TOMOYO Linux Cross Reference
Linux/kernel/events/core.c

   /*
    * Performance events core code:
    *
    *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
    *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
    *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra
    *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
    *
    * For licensing details see kernel-base/COPYING
   */
  
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/cpu.h>
  #include <linux/smp.h>
  #include <linux/idr.h>
  #include <linux/file.h>
  #include <linux/poll.h>
  #include <linux/slab.h>
  #include <linux/hash.h>
  #include <linux/tick.h>
  #include <linux/sysfs.h>
  #include <linux/dcache.h>
  #include <linux/percpu.h>
  #include <linux/ptrace.h>
  #include <linux/reboot.h>
  #include <linux/vmstat.h>
  #include <linux/device.h>
  #include <linux/export.h>
  #include <linux/vmalloc.h>
  #include <linux/hardirq.h>
  #include <linux/rculist.h>
  #include <linux/uaccess.h>
  #include <linux/syscalls.h>
  #include <linux/anon_inodes.h>
  #include <linux/kernel_stat.h>
  #include <linux/cgroup.h>
  #include <linux/perf_event.h>
  #include <linux/trace_events.h>
  #include <linux/hw_breakpoint.h>
  #include <linux/mm_types.h>
  #include <linux/module.h>
  #include <linux/mman.h>
  #include <linux/compat.h>
  #include <linux/bpf.h>
  #include <linux/filter.h>
  #include <linux/namei.h>
  #include <linux/parser.h>
  
  #include "internal.h"
  
  #include <asm/irq_regs.h>
  
  typedef int (*remote_function_f)(void *);
  
  struct remote_function_call {
          struct task_struct      *p;
          remote_function_f       func;
          void                    *info;
          int                     ret;
  };
  
  static void remote_function(void *data)
  {
          struct remote_function_call *tfc = data;
          struct task_struct *p = tfc->p;
  
          if (p) {
                  /* -EAGAIN */
                  if (task_cpu(p) != smp_processor_id())
                          return;
  
                  /*
                   * Now that we're on right CPU with IRQs disabled, we can test
                   * if we hit the right task without races.
                   */
  
                  tfc->ret = -ESRCH; /* No such (running) process */
                  if (p != current)
                          return;
          }
  
          tfc->ret = tfc->func(tfc->info);
  }
  
  /**
   * task_function_call - call a function on the cpu on which a task runs
   * @p:          the task to evaluate
   * @func:       the function to be called
   * @info:       the function call argument
   *
   * Calls the function @func when the task is currently running. This might
   * be on the current CPU, which just calls the function directly
   *
   * returns: @func return value, or
   *          -ESRCH  - when the process isn't running
   *          -EAGAIN - when the process moved away
   */
  static int
 task_function_call(struct task_struct *p, remote_function_f func, void *info)
 {
         struct remote_function_call data = {
                 .p      = p,
                 .func   = func,
                 .info   = info,
                 .ret    = -EAGAIN,
         };
         int ret;
 
         do {
                 ret = smp_call_function_single(task_cpu(p), remote_function, &data, 1);
                 if (!ret)
                         ret = data.ret;
         } while (ret == -EAGAIN);
 
         return ret;
 }
 
 /**
  * cpu_function_call - call a function on the cpu
  * @func:       the function to be called
  * @info:       the function call argument
  *
  * Calls the function @func on the remote cpu.
  *
  * returns: @func return value or -ENXIO when the cpu is offline
  */
 static int cpu_function_call(int cpu, remote_function_f func, void *info)
 {
         struct remote_function_call data = {
                 .p      = NULL,
                 .func   = func,
                 .info   = info,
                 .ret    = -ENXIO, /* No such CPU */
         };
 
         smp_call_function_single(cpu, remote_function, &data, 1);
 
         return data.ret;
 }
 
 static inline struct perf_cpu_context *
 __get_cpu_context(struct perf_event_context *ctx)
 {
         return this_cpu_ptr(ctx->pmu->pmu_cpu_context);
 }
 
 static void perf_ctx_lock(struct perf_cpu_context *cpuctx,
                           struct perf_event_context *ctx)
 {
         raw_spin_lock(&cpuctx->ctx.lock);
         if (ctx)
                 raw_spin_lock(&ctx->lock);
 }
 
 static void perf_ctx_unlock(struct perf_cpu_context *cpuctx,
                             struct perf_event_context *ctx)
 {
         if (ctx)
                 raw_spin_unlock(&ctx->lock);
         raw_spin_unlock(&cpuctx->ctx.lock);
 }
 
 #define TASK_TOMBSTONE ((void *)-1L)
 
 static bool is_kernel_event(struct perf_event *event)
 {
         return READ_ONCE(event->owner) == TASK_TOMBSTONE;
 }
 
 /*
  * On task ctx scheduling...
  *
  * When !ctx->nr_events a task context will not be scheduled. This means
  * we can disable the scheduler hooks (for performance) without leaving
  * pending task ctx state.
  *
  * This however results in two special cases:
  *
  *  - removing the last event from a task ctx; this is relatively straight
  *    forward and is done in __perf_remove_from_context.
  *
  *  - adding the first event to a task ctx; this is tricky because we cannot
  *    rely on ctx->is_active and therefore cannot use event_function_call().
  *    See perf_install_in_context().
  *
  * If ctx->nr_events, then ctx->is_active and cpuctx->task_ctx are set.
  */
 
 typedef void (*event_f)(struct perf_event *, struct perf_cpu_context *,
                         struct perf_event_context *, void *);
 
 struct event_function_struct {
         struct perf_event *event;
         event_f func;
         void *data;
 };
 
 static int event_function(void *info)
 {
         struct event_function_struct *efs = info;
         struct perf_event *event = efs->event;
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
         struct perf_event_context *task_ctx = cpuctx->task_ctx;
         int ret = 0;
 
         WARN_ON_ONCE(!irqs_disabled());
 
         perf_ctx_lock(cpuctx, task_ctx);
         /*
          * Since we do the IPI call without holding ctx->lock things can have
          * changed, double check we hit the task we set out to hit.
          */
         if (ctx->task) {
                 if (ctx->task != current) {
                         ret = -ESRCH;
                         goto unlock;
                 }
 
                 /*
                  * We only use event_function_call() on established contexts,
                  * and event_function() is only ever called when active (or
                  * rather, we'll have bailed in task_function_call() or the
                  * above ctx->task != current test), therefore we must have
                  * ctx->is_active here.
                  */
                 WARN_ON_ONCE(!ctx->is_active);
                 /*
                  * And since we have ctx->is_active, cpuctx->task_ctx must
                  * match.
                  */
                 WARN_ON_ONCE(task_ctx != ctx);
         } else {
                 WARN_ON_ONCE(&cpuctx->ctx != ctx);
         }
 
         efs->func(event, cpuctx, ctx, efs->data);
 unlock:
         perf_ctx_unlock(cpuctx, task_ctx);
 
         return ret;
 }
 
 static void event_function_call(struct perf_event *event, event_f func, void *data)
 {
         struct perf_event_context *ctx = event->ctx;
         struct task_struct *task = READ_ONCE(ctx->task); /* verified in event_function */
         struct event_function_struct efs = {
                 .event = event,
                 .func = func,
                 .data = data,
         };
 
         if (!event->parent) {
                 /*
                  * If this is a !child event, we must hold ctx::mutex to
                  * stabilize the the event->ctx relation. See
                  * perf_event_ctx_lock().
                  */
                 lockdep_assert_held(&ctx->mutex);
         }
 
         if (!task) {
                 cpu_function_call(event->cpu, event_function, &efs);
                 return;
         }
 
         if (task == TASK_TOMBSTONE)
                 return;
 
 again:
         if (!task_function_call(task, event_function, &efs))
                 return;
 
         raw_spin_lock_irq(&ctx->lock);
         /*
          * Reload the task pointer, it might have been changed by
          * a concurrent perf_event_context_sched_out().
          */
         task = ctx->task;
         if (task == TASK_TOMBSTONE) {
                 raw_spin_unlock_irq(&ctx->lock);
                 return;
         }
         if (ctx->is_active) {
                 raw_spin_unlock_irq(&ctx->lock);
                 goto again;
         }
         func(event, NULL, ctx, data);
         raw_spin_unlock_irq(&ctx->lock);
 }
 
 /*
  * Similar to event_function_call() + event_function(), but hard assumes IRQs
  * are already disabled and we're on the right CPU.
  */
 static void event_function_local(struct perf_event *event, event_f func, void *data)
 {
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
         struct task_struct *task = READ_ONCE(ctx->task);
         struct perf_event_context *task_ctx = NULL;
 
         WARN_ON_ONCE(!irqs_disabled());
 
         if (task) {
                 if (task == TASK_TOMBSTONE)
                         return;
 
                 task_ctx = ctx;
         }
 
         perf_ctx_lock(cpuctx, task_ctx);
 
         task = ctx->task;
         if (task == TASK_TOMBSTONE)
                 goto unlock;
 
         if (task) {
                 /*
                  * We must be either inactive or active and the right task,
                  * otherwise we're screwed, since we cannot IPI to somewhere
                  * else.
                  */
                 if (ctx->is_active) {
                         if (WARN_ON_ONCE(task != current))
                                 goto unlock;
 
                         if (WARN_ON_ONCE(cpuctx->task_ctx != ctx))
                                 goto unlock;
                 }
         } else {
                 WARN_ON_ONCE(&cpuctx->ctx != ctx);
         }
 
         func(event, cpuctx, ctx, data);
 unlock:
         perf_ctx_unlock(cpuctx, task_ctx);
 }
 
 #define PERF_FLAG_ALL (PERF_FLAG_FD_NO_GROUP |\
                        PERF_FLAG_FD_OUTPUT  |\
                        PERF_FLAG_PID_CGROUP |\
                        PERF_FLAG_FD_CLOEXEC)
 
 /*
  * branch priv levels that need permission checks
  */
 #define PERF_SAMPLE_BRANCH_PERM_PLM \
         (PERF_SAMPLE_BRANCH_KERNEL |\
          PERF_SAMPLE_BRANCH_HV)
 
 enum event_type_t {
         EVENT_FLEXIBLE = 0x1,
         EVENT_PINNED = 0x2,
         EVENT_TIME = 0x4,
         EVENT_ALL = EVENT_FLEXIBLE | EVENT_PINNED,
 };
 
 /*
  * perf_sched_events : >0 events exist
  * perf_cgroup_events: >0 per-cpu cgroup events exist on this cpu
  */
 
 static void perf_sched_delayed(struct work_struct *work);
 DEFINE_STATIC_KEY_FALSE(perf_sched_events);
 static DECLARE_DELAYED_WORK(perf_sched_work, perf_sched_delayed);
 static DEFINE_MUTEX(perf_sched_mutex);
 static atomic_t perf_sched_count;
 
 static DEFINE_PER_CPU(atomic_t, perf_cgroup_events);
 static DEFINE_PER_CPU(int, perf_sched_cb_usages);
 
 static atomic_t nr_mmap_events __read_mostly;
 static atomic_t nr_comm_events __read_mostly;
 static atomic_t nr_task_events __read_mostly;
 static atomic_t nr_freq_events __read_mostly;
 static atomic_t nr_switch_events __read_mostly;
 
 static LIST_HEAD(pmus);
 static DEFINE_MUTEX(pmus_lock);
 static struct srcu_struct pmus_srcu;
 
 /*
  * perf event paranoia level:
  *  -1 - not paranoid at all
  *   0 - disallow raw tracepoint access for unpriv
  *   1 - disallow cpu events for unpriv
  *   2 - disallow kernel profiling for unpriv
  */
 int sysctl_perf_event_paranoid __read_mostly = 2;
 
 /* Minimum for 512 kiB + 1 user control page */
 int sysctl_perf_event_mlock __read_mostly = 512 + (PAGE_SIZE / 1024); /* 'free' kiB per user */
 
 /*
  * max perf event sample rate
  */
 #define DEFAULT_MAX_SAMPLE_RATE         100000
 #define DEFAULT_SAMPLE_PERIOD_NS        (NSEC_PER_SEC / DEFAULT_MAX_SAMPLE_RATE)
 #define DEFAULT_CPU_TIME_MAX_PERCENT    25
 
 int sysctl_perf_event_sample_rate __read_mostly = DEFAULT_MAX_SAMPLE_RATE;
 
 static int max_samples_per_tick __read_mostly   = DIV_ROUND_UP(DEFAULT_MAX_SAMPLE_RATE, HZ);
 static int perf_sample_period_ns __read_mostly  = DEFAULT_SAMPLE_PERIOD_NS;
 
 static int perf_sample_allowed_ns __read_mostly =
         DEFAULT_SAMPLE_PERIOD_NS * DEFAULT_CPU_TIME_MAX_PERCENT / 100;
 
 static void update_perf_cpu_limits(void)
 {
         u64 tmp = perf_sample_period_ns;
 
         tmp *= sysctl_perf_cpu_time_max_percent;
         tmp = div_u64(tmp, 100);
         if (!tmp)
                 tmp = 1;
 
         WRITE_ONCE(perf_sample_allowed_ns, tmp);
 }
 
 static int perf_rotate_context(struct perf_cpu_context *cpuctx);
 
 int perf_proc_update_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos)
 {
         int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 
         if (ret || !write)
                 return ret;
 
         max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ);
         perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
         update_perf_cpu_limits();
 
         return 0;
 }
 
 int sysctl_perf_cpu_time_max_percent __read_mostly = DEFAULT_CPU_TIME_MAX_PERCENT;
 
 int perf_cpu_time_max_percent_handler(struct ctl_table *table, int write,
                                 void __user *buffer, size_t *lenp,
                                 loff_t *ppos)
 {
         int ret = proc_dointvec(table, write, buffer, lenp, ppos);
 
         if (ret || !write)
                 return ret;
 
         if (sysctl_perf_cpu_time_max_percent == 100 ||
             sysctl_perf_cpu_time_max_percent == 0) {
                 printk(KERN_WARNING
                        "perf: Dynamic interrupt throttling disabled, can hang your system!\n");
                 WRITE_ONCE(perf_sample_allowed_ns, 0);
         } else {
                 update_perf_cpu_limits();
         }
 
         return 0;
 }
 
 /*
  * perf samples are done in some very critical code paths (NMIs).
  * If they take too much CPU time, the system can lock up and not
  * get any real work done.  This will drop the sample rate when
  * we detect that events are taking too long.
  */
 #define NR_ACCUMULATED_SAMPLES 128
 static DEFINE_PER_CPU(u64, running_sample_length);
 
 static u64 __report_avg;
 static u64 __report_allowed;
 
 static void perf_duration_warn(struct irq_work *w)
 {
         printk_ratelimited(KERN_WARNING
                 "perf: interrupt took too long (%lld > %lld), lowering "
                 "kernel.perf_event_max_sample_rate to %d\n",
                 __report_avg, __report_allowed,
                 sysctl_perf_event_sample_rate);
 }
 
 static DEFINE_IRQ_WORK(perf_duration_work, perf_duration_warn);
 
 void perf_sample_event_took(u64 sample_len_ns)
 {
         u64 max_len = READ_ONCE(perf_sample_allowed_ns);
         u64 running_len;
         u64 avg_len;
         u32 max;
 
         if (max_len == 0)
                 return;
 
         /* Decay the counter by 1 average sample. */
         running_len = __this_cpu_read(running_sample_length);
         running_len -= running_len/NR_ACCUMULATED_SAMPLES;
         running_len += sample_len_ns;
         __this_cpu_write(running_sample_length, running_len);
 
         /*
          * Note: this will be biased artifically low until we have
          * seen NR_ACCUMULATED_SAMPLES. Doing it this way keeps us
          * from having to maintain a count.
          */
         avg_len = running_len/NR_ACCUMULATED_SAMPLES;
         if (avg_len <= max_len)
                 return;
 
         __report_avg = avg_len;
         __report_allowed = max_len;
 
         /*
          * Compute a throttle threshold 25% below the current duration.
          */
         avg_len += avg_len / 4;
         max = (TICK_NSEC / 100) * sysctl_perf_cpu_time_max_percent;
         if (avg_len < max)
                 max /= (u32)avg_len;
         else
                 max = 1;
 
         WRITE_ONCE(perf_sample_allowed_ns, avg_len);
         WRITE_ONCE(max_samples_per_tick, max);
 
         sysctl_perf_event_sample_rate = max * HZ;
         perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate;
 
         if (!irq_work_queue(&perf_duration_work)) {
                 early_printk("perf: interrupt took too long (%lld > %lld), lowering "
                              "kernel.perf_event_max_sample_rate to %d\n",
                              __report_avg, __report_allowed,
                              sysctl_perf_event_sample_rate);
         }
 }
 
 static atomic64_t perf_event_id;
 
 static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                               enum event_type_t event_type);
 
 static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                              enum event_type_t event_type,
                              struct task_struct *task);
 
 static void update_context_time(struct perf_event_context *ctx);
 static u64 perf_event_time(struct perf_event *event);
 
 void __weak perf_event_print_debug(void)        { }
 
 extern __weak const char *perf_pmu_name(void)
 {
         return "pmu";
 }
 
 static inline u64 perf_clock(void)
 {
         return local_clock();
 }
 
 static inline u64 perf_event_clock(struct perf_event *event)
 {
         return event->clock();
 }
 
 #ifdef CONFIG_CGROUP_PERF
 
 static inline bool
 perf_cgroup_match(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
 
         /* @event doesn't care about cgroup */
         if (!event->cgrp)
                 return true;
 
         /* wants specific cgroup scope but @cpuctx isn't associated with any */
         if (!cpuctx->cgrp)
                 return false;
 
         /*
          * Cgroup scoping is recursive.  An event enabled for a cgroup is
          * also enabled for all its descendant cgroups.  If @cpuctx's
          * cgroup is a descendant of @event's (the test covers identity
          * case), it's a match.
          */
         return cgroup_is_descendant(cpuctx->cgrp->css.cgroup,
                                     event->cgrp->css.cgroup);
 }
 
 static inline void perf_detach_cgroup(struct perf_event *event)
 {
         css_put(&event->cgrp->css);
         event->cgrp = NULL;
 }
 
 static inline int is_cgroup_event(struct perf_event *event)
 {
         return event->cgrp != NULL;
 }
 
 static inline u64 perf_cgroup_event_time(struct perf_event *event)
 {
         struct perf_cgroup_info *t;
 
         t = per_cpu_ptr(event->cgrp->info, event->cpu);
         return t->time;
 }
 
 static inline void __update_cgrp_time(struct perf_cgroup *cgrp)
 {
         struct perf_cgroup_info *info;
         u64 now;
 
         now = perf_clock();
 
         info = this_cpu_ptr(cgrp->info);
 
         info->time += now - info->timestamp;
         info->timestamp = now;
 }
 
 static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
 {
         struct perf_cgroup *cgrp_out = cpuctx->cgrp;
         if (cgrp_out)
                 __update_cgrp_time(cgrp_out);
 }
 
 static inline void update_cgrp_time_from_event(struct perf_event *event)
 {
         struct perf_cgroup *cgrp;
 
         /*
          * ensure we access cgroup data only when needed and
          * when we know the cgroup is pinned (css_get)
          */
         if (!is_cgroup_event(event))
                 return;
 
         cgrp = perf_cgroup_from_task(current, event->ctx);
         /*
          * Do not update time when cgroup is not active
          */
         if (cgrp == event->cgrp)
                 __update_cgrp_time(event->cgrp);
 }
 
 static inline void
 perf_cgroup_set_timestamp(struct task_struct *task,
                           struct perf_event_context *ctx)
 {
         struct perf_cgroup *cgrp;
         struct perf_cgroup_info *info;
 
         /*
          * ctx->lock held by caller
          * ensure we do not access cgroup data
          * unless we have the cgroup pinned (css_get)
          */
         if (!task || !ctx->nr_cgroups)
                 return;
 
         cgrp = perf_cgroup_from_task(task, ctx);
         info = this_cpu_ptr(cgrp->info);
         info->timestamp = ctx->timestamp;
 }
 
 #define PERF_CGROUP_SWOUT       0x1 /* cgroup switch out every event */
 #define PERF_CGROUP_SWIN        0x2 /* cgroup switch in events based on task */
 
 /*
  * reschedule events based on the cgroup constraint of task.
  *
  * mode SWOUT : schedule out everything
  * mode SWIN : schedule in based on cgroup for next
  */
 static void perf_cgroup_switch(struct task_struct *task, int mode)
 {
         struct perf_cpu_context *cpuctx;
         struct pmu *pmu;
         unsigned long flags;
 
         /*
          * disable interrupts to avoid geting nr_cgroup
          * changes via __perf_event_disable(). Also
          * avoids preemption.
          */
         local_irq_save(flags);
 
         /*
          * we reschedule only in the presence of cgroup
          * constrained events.
          */
 
         list_for_each_entry_rcu(pmu, &pmus, entry) {
                 cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
                 if (cpuctx->unique_pmu != pmu)
                         continue; /* ensure we process each cpuctx once */
 
                 /*
                  * perf_cgroup_events says at least one
                  * context on this CPU has cgroup events.
                  *
                  * ctx->nr_cgroups reports the number of cgroup
                  * events for a context.
                  */
                 if (cpuctx->ctx.nr_cgroups > 0) {
                         perf_ctx_lock(cpuctx, cpuctx->task_ctx);
                         perf_pmu_disable(cpuctx->ctx.pmu);
 
                         if (mode & PERF_CGROUP_SWOUT) {
                                 cpu_ctx_sched_out(cpuctx, EVENT_ALL);
                                 /*
                                  * must not be done before ctxswout due
                                  * to event_filter_match() in event_sched_out()
                                  */
                                 cpuctx->cgrp = NULL;
                         }
 
                         if (mode & PERF_CGROUP_SWIN) {
                                 WARN_ON_ONCE(cpuctx->cgrp);
                                 /*
                                  * set cgrp before ctxsw in to allow
                                  * event_filter_match() to not have to pass
                                  * task around
                                  * we pass the cpuctx->ctx to perf_cgroup_from_task()
                                  * because cgorup events are only per-cpu
                                  */
                                 cpuctx->cgrp = perf_cgroup_from_task(task, &cpuctx->ctx);
                                 cpu_ctx_sched_in(cpuctx, EVENT_ALL, task);
                         }
                         perf_pmu_enable(cpuctx->ctx.pmu);
                         perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
                 }
         }
 
         local_irq_restore(flags);
 }
 
 static inline void perf_cgroup_sched_out(struct task_struct *task,
                                          struct task_struct *next)
 {
         struct perf_cgroup *cgrp1;
         struct perf_cgroup *cgrp2 = NULL;
 
         rcu_read_lock();
         /*
          * we come here when we know perf_cgroup_events > 0
          * we do not need to pass the ctx here because we know
          * we are holding the rcu lock
          */
         cgrp1 = perf_cgroup_from_task(task, NULL);
         cgrp2 = perf_cgroup_from_task(next, NULL);
 
         /*
          * only schedule out current cgroup events if we know
          * that we are switching to a different cgroup. Otherwise,
          * do no touch the cgroup events.
          */
         if (cgrp1 != cgrp2)
                 perf_cgroup_switch(task, PERF_CGROUP_SWOUT);
 
         rcu_read_unlock();
 }
 
 static inline void perf_cgroup_sched_in(struct task_struct *prev,
                                         struct task_struct *task)
 {
         struct perf_cgroup *cgrp1;
         struct perf_cgroup *cgrp2 = NULL;
 
         rcu_read_lock();
         /*
          * we come here when we know perf_cgroup_events > 0
          * we do not need to pass the ctx here because we know
          * we are holding the rcu lock
          */
         cgrp1 = perf_cgroup_from_task(task, NULL);
         cgrp2 = perf_cgroup_from_task(prev, NULL);
 
         /*
          * only need to schedule in cgroup events if we are changing
          * cgroup during ctxsw. Cgroup events were not scheduled
          * out of ctxsw out if that was not the case.
          */
         if (cgrp1 != cgrp2)
                 perf_cgroup_switch(task, PERF_CGROUP_SWIN);
 
         rcu_read_unlock();
 }
 
 static inline int perf_cgroup_connect(int fd, struct perf_event *event,
                                       struct perf_event_attr *attr,
                                       struct perf_event *group_leader)
 {
         struct perf_cgroup *cgrp;
         struct cgroup_subsys_state *css;
         struct fd f = fdget(fd);
         int ret = 0;
 
         if (!f.file)
                 return -EBADF;
 
         css = css_tryget_online_from_dir(f.file->f_path.dentry,
                                          &perf_event_cgrp_subsys);
         if (IS_ERR(css)) {
                 ret = PTR_ERR(css);
                 goto out;
         }
 
         cgrp = container_of(css, struct perf_cgroup, css);
         event->cgrp = cgrp;
 
         /*
          * all events in a group must monitor
          * the same cgroup because a task belongs
          * to only one perf cgroup at a time
          */
         if (group_leader && group_leader->cgrp != cgrp) {
                 perf_detach_cgroup(event);
                 ret = -EINVAL;
         }
 out:
         fdput(f);
         return ret;
 }
 
 static inline void
 perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
 {
         struct perf_cgroup_info *t;
         t = per_cpu_ptr(event->cgrp->info, event->cpu);
         event->shadow_ctx_time = now - t->timestamp;
 }
 
 static inline void
 perf_cgroup_defer_enabled(struct perf_event *event)
 {
         /*
          * when the current task's perf cgroup does not match
          * the event's, we need to remember to call the
          * perf_mark_enable() function the first time a task with
          * a matching perf cgroup is scheduled in.
          */
         if (is_cgroup_event(event) && !perf_cgroup_match(event))
                 event->cgrp_defer_enabled = 1;
 }
 
 static inline void
 perf_cgroup_mark_enabled(struct perf_event *event,
                          struct perf_event_context *ctx)
 {
         struct perf_event *sub;
         u64 tstamp = perf_event_time(event);
 
         if (!event->cgrp_defer_enabled)
                 return;
 
         event->cgrp_defer_enabled = 0;
 
         event->tstamp_enabled = tstamp - event->total_time_enabled;
         list_for_each_entry(sub, &event->sibling_list, group_entry) {
                 if (sub->state >= PERF_EVENT_STATE_INACTIVE) {
                         sub->tstamp_enabled = tstamp - sub->total_time_enabled;
                         sub->cgrp_defer_enabled = 0;
                 }
         }
 }
 #else /* !CONFIG_CGROUP_PERF */
 
 static inline bool
 perf_cgroup_match(struct perf_event *event)
 {
         return true;
 }
 
 static inline void perf_detach_cgroup(struct perf_event *event)
 {}
 
 static inline int is_cgroup_event(struct perf_event *event)
 {
         return 0;
 }
 
 static inline u64 perf_cgroup_event_cgrp_time(struct perf_event *event)
 {
         return 0;
 }
 
 static inline void update_cgrp_time_from_event(struct perf_event *event)
 {
 }
 
 static inline void update_cgrp_time_from_cpuctx(struct perf_cpu_context *cpuctx)
 {
 }
 
 static inline void perf_cgroup_sched_out(struct task_struct *task,
                                          struct task_struct *next)
 {
 }
 
 static inline void perf_cgroup_sched_in(struct task_struct *prev,
                                         struct task_struct *task)
 {
 }
 
 static inline int perf_cgroup_connect(pid_t pid, struct perf_event *event,
                                       struct perf_event_attr *attr,
                                       struct perf_event *group_leader)
 {
         return -EINVAL;
 }
 
 static inline void
 perf_cgroup_set_timestamp(struct task_struct *task,
                           struct perf_event_context *ctx)
 {
 }
 
 void
 perf_cgroup_switch(struct task_struct *task, struct task_struct *next)
 {
 }
 
 static inline void
 perf_cgroup_set_shadow_time(struct perf_event *event, u64 now)
 {
 }
 
 static inline u64 perf_cgroup_event_time(struct perf_event *event)
 {
         return 0;
 }
 
 static inline void
 perf_cgroup_defer_enabled(struct perf_event *event)
 {
 }
 
 static inline void
 perf_cgroup_mark_enabled(struct perf_event *event,
                          struct perf_event_context *ctx)
 {
 }
 #endif
 
 /*
  * set default to be dependent on timer tick just
  * like original code
  */
 #define PERF_CPU_HRTIMER (1000 / HZ)
 /*
  * function must be called with interrupts disbled
  */
 static enum hrtimer_restart perf_mux_hrtimer_handler(struct hrtimer *hr)
 {
         struct perf_cpu_context *cpuctx;
         int rotations = 0;
 
         WARN_ON(!irqs_disabled());
 
         cpuctx = container_of(hr, struct perf_cpu_context, hrtimer);
         rotations = perf_rotate_context(cpuctx);
 
         raw_spin_lock(&cpuctx->hrtimer_lock);
         if (rotations)
                 hrtimer_forward_now(hr, cpuctx->hrtimer_interval);
         else
                 cpuctx->hrtimer_active = 0;
         raw_spin_unlock(&cpuctx->hrtimer_lock);
 
         return rotations ? HRTIMER_RESTART : HRTIMER_NORESTART;
 }
 
 static void __perf_mux_hrtimer_init(struct perf_cpu_context *cpuctx, int cpu)
 {
         struct hrtimer *timer = &cpuctx->hrtimer;
         struct pmu *pmu = cpuctx->ctx.pmu;
         u64 interval;
 
         /* no multiplexing needed for SW PMU */
         if (pmu->task_ctx_nr == perf_sw_context)
                 return;
 
         /*
          * check default is sane, if not set then force to
          * default interval (1/tick)
          */
         interval = pmu->hrtimer_interval_ms;
         if (interval < 1)
                 interval = pmu->hrtimer_interval_ms = PERF_CPU_HRTIMER;
 
         cpuctx->hrtimer_interval = ns_to_ktime(NSEC_PER_MSEC * interval);
 
         raw_spin_lock_init(&cpuctx->hrtimer_lock);
         hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED);
         timer->function = perf_mux_hrtimer_handler;
 }
 
 static int perf_mux_hrtimer_restart(struct perf_cpu_context *cpuctx)
 {
         struct hrtimer *timer = &cpuctx->hrtimer;
         struct pmu *pmu = cpuctx->ctx.pmu;
         unsigned long flags;
 
         /* not for SW PMU */
         if (pmu->task_ctx_nr == perf_sw_context)
                 return 0;
 
         raw_spin_lock_irqsave(&cpuctx->hrtimer_lock, flags);
         if (!cpuctx->hrtimer_active) {
                 cpuctx->hrtimer_active = 1;
                 hrtimer_forward_now(timer, cpuctx->hrtimer_interval);
                 hrtimer_start_expires(timer, HRTIMER_MODE_ABS_PINNED);
         }
         raw_spin_unlock_irqrestore(&cpuctx->hrtimer_lock, flags);
 
         return 0;
 }
 
 void perf_pmu_disable(struct pmu *pmu)
 {
         int *count = this_cpu_ptr(pmu->pmu_disable_count);
         if (!(*count)++)
                 pmu->pmu_disable(pmu);
 }
 
 void perf_pmu_enable(struct pmu *pmu)
 {
         int *count = this_cpu_ptr(pmu->pmu_disable_count);
         if (!--(*count))
                 pmu->pmu_enable(pmu);
 }
 
 static DEFINE_PER_CPU(struct list_head, active_ctx_list);
 
 /*
  * perf_event_ctx_activate(), perf_event_ctx_deactivate(), and
  * perf_event_task_tick() are fully serialized because they're strictly cpu
  * affine and perf_event_ctx{activate,deactivate} are called with IRQs
  * disabled, while perf_event_task_tick is called from IRQ context.
  */
 static void perf_event_ctx_activate(struct perf_event_context *ctx)
 {
         struct list_head *head = this_cpu_ptr(&active_ctx_list);
 
         WARN_ON(!irqs_disabled());
 
         WARN_ON(!list_empty(&ctx->active_ctx_list));
 
         list_add(&ctx->active_ctx_list, head);
 }
 
 static void perf_event_ctx_deactivate(struct perf_event_context *ctx)
 {
         WARN_ON(!irqs_disabled());
 
         WARN_ON(list_empty(&ctx->active_ctx_list));
 
         list_del_init(&ctx->active_ctx_list);
 }
 
 static void get_ctx(struct perf_event_context *ctx)
 {
         WARN_ON(!atomic_inc_not_zero(&ctx->refcount));
 }
 
 static void free_ctx(struct rcu_head *head)
 {
         struct perf_event_context *ctx;
 
         ctx = container_of(head, struct perf_event_context, rcu_head);
         kfree(ctx->task_ctx_data);
         kfree(ctx);
 }
 
 static void put_ctx(struct perf_event_context *ctx)
 {
         if (atomic_dec_and_test(&ctx->refcount)) {
                 if (ctx->parent_ctx)
                         put_ctx(ctx->parent_ctx);
                 if (ctx->task && ctx->task != TASK_TOMBSTONE)
                         put_task_struct(ctx->task);
                 call_rcu(&ctx->rcu_head, free_ctx);
         }
 }
 
 /*
  * Because of perf_event::ctx migration in sys_perf_event_open::move_group and
  * perf_pmu_migrate_context() we need some magic.
  *
  * Those places that change perf_event::ctx will hold both
  * perf_event_ctx::mutex of the 'old' and 'new' ctx value.
  *
  * Lock ordering is by mutex address. There are two other sites where
  * perf_event_context::mutex nests and those are:
  *
  *  - perf_event_exit_task_context()    [ child , 0 ]
  *      perf_event_exit_event()
  *        put_event()                   [ parent, 1 ]
  *
  *  - perf_event_init_context()         [ parent, 0 ]
  *      inherit_task_group()
  *        inherit_group()
  *          inherit_event()
  *            perf_event_alloc()
  *              perf_init_event()
  *                perf_try_init_event() [ child , 1 ]
  *
  * While it appears there is an obvious deadlock here -- the parent and child
  * nesting levels are inverted between the two. This is in fact safe because
  * life-time rules separate them. That is an exiting task cannot fork, and a
  * spawning task cannot (yet) exit.
  *
  * But remember that that these are parent<->child context relations, and
  * migration does not affect children, therefore these two orderings should not
  * interact.
  *
  * The change in perf_event::ctx does not affect children (as claimed above)
  * because the sys_perf_event_open() case will install a new event and break
  * the ctx parent<->child relation, and perf_pmu_migrate_context() is only
  * concerned with cpuctx and that doesn't have children.
  *
  * The places that change perf_event::ctx will issue:
  *
  *   perf_remove_from_context();
  *   synchronize_rcu();
  *   perf_install_in_context();
  *
  * to affect the change. The remove_from_context() + synchronize_rcu() should
  * quiesce the event, after which we can install it in the new location. This
  * means that only external vectors (perf_fops, prctl) can perturb the event
  * while in transit. Therefore all such accessors should also acquire
  * perf_event_context::mutex to serialize against this.
  *
  * However; because event->ctx can change while we're waiting to acquire
  * ctx->mutex we must be careful and use the below perf_event_ctx_lock()
  * function.
  *
  * Lock order:
  *    cred_guard_mutex
  *      task_struct::perf_event_mutex
  *        perf_event_context::mutex
  *          perf_event::child_mutex;
  *            perf_event_context::lock
  *          perf_event::mmap_mutex
  *          mmap_sem
  */
 static struct perf_event_context *
 perf_event_ctx_lock_nested(struct perf_event *event, int nesting)
 {
         struct perf_event_context *ctx;
 
 again:
         rcu_read_lock();
         ctx = ACCESS_ONCE(event->ctx);
         if (!atomic_inc_not_zero(&ctx->refcount)) {
                 rcu_read_unlock();
                 goto again;
         }
         rcu_read_unlock();
 
         mutex_lock_nested(&ctx->mutex, nesting);
         if (event->ctx != ctx) {
                 mutex_unlock(&ctx->mutex);
                 put_ctx(ctx);
                 goto again;
         }
 
         return ctx;
 }
 
 static inline struct perf_event_context *
 perf_event_ctx_lock(struct perf_event *event)
 {
         return perf_event_ctx_lock_nested(event, 0);
 }
 
 static void perf_event_ctx_unlock(struct perf_event *event,
                                   struct perf_event_context *ctx)
 {
         mutex_unlock(&ctx->mutex);
         put_ctx(ctx);
 }
 
 /*
  * This must be done under the ctx->lock, such as to serialize against
  * context_equiv(), therefore we cannot call put_ctx() since that might end up
  * calling scheduler related locks and ctx->lock nests inside those.
  */
 static __must_check struct perf_event_context *
 unclone_ctx(struct perf_event_context *ctx)
 {
         struct perf_event_context *parent_ctx = ctx->parent_ctx;
 
         lockdep_assert_held(&ctx->lock);
 
         if (parent_ctx)
                 ctx->parent_ctx = NULL;
         ctx->generation++;
 
         return parent_ctx;
 }
 
 static u32 perf_event_pid(struct perf_event *event, struct task_struct *p)
 {
         /*
          * only top level events have the pid namespace they were created in
          */
         if (event->parent)
                 event = event->parent;
 
         return task_tgid_nr_ns(p, event->ns);
 }
 
 static u32 perf_event_tid(struct perf_event *event, struct task_struct *p)
 {
         /*
          * only top level events have the pid namespace they were created in
          */
         if (event->parent)
                 event = event->parent;
 
         return task_pid_nr_ns(p, event->ns);
 }
 
 /*
  * If we inherit events we want to return the parent event id
  * to userspace.
  */
 static u64 primary_event_id(struct perf_event *event)
 {
         u64 id = event->id;
 
         if (event->parent)
                 id = event->parent->id;
 
         return id;
 }
 
 /*
  * Get the perf_event_context for a task and lock it.
  *
  * This has to cope with with the fact that until it is locked,
  * the context could get moved to another task.
  */
 static struct perf_event_context *
 perf_lock_task_context(struct task_struct *task, int ctxn, unsigned long *flags)
 {
         struct perf_event_context *ctx;
 
 retry:
         /*
          * One of the few rules of preemptible RCU is that one cannot do
          * rcu_read_unlock() while holding a scheduler (or nested) lock when
          * part of the read side critical section was irqs-enabled -- see
          * rcu_read_unlock_special().
          *
          * Since ctx->lock nests under rq->lock we must ensure the entire read
          * side critical section has interrupts disabled.
          */
         local_irq_save(*flags);
         rcu_read_lock();
         ctx = rcu_dereference(task->perf_event_ctxp[ctxn]);
         if (ctx) {
                 /*
                  * If this context is a clone of another, it might
                  * get swapped for another underneath us by
                  * perf_event_task_sched_out, though the
                  * rcu_read_lock() protects us from any context
                  * getting freed.  Lock the context and check if it
                  * got swapped before we could get the lock, and retry
                  * if so.  If we locked the right context, then it
                  * can't get swapped on us any more.
                  */
                 raw_spin_lock(&ctx->lock);
                 if (ctx != rcu_dereference(task->perf_event_ctxp[ctxn])) {
                         raw_spin_unlock(&ctx->lock);
                         rcu_read_unlock();
                         local_irq_restore(*flags);
                         goto retry;
                 }
 
                 if (ctx->task == TASK_TOMBSTONE ||
                     !atomic_inc_not_zero(&ctx->refcount)) {
                         raw_spin_unlock(&ctx->lock);
                         ctx = NULL;
                 } else {
                         WARN_ON_ONCE(ctx->task != task);
                 }
         }
         rcu_read_unlock();
         if (!ctx)
                 local_irq_restore(*flags);
         return ctx;
 }
 
 /*
  * Get the context for a task and increment its pin_count so it
  * can't get swapped to another task.  This also increments its
  * reference count so that the context can't get freed.
  */
 static struct perf_event_context *
 perf_pin_task_context(struct task_struct *task, int ctxn)
 {
         struct perf_event_context *ctx;
         unsigned long flags;
 
         ctx = perf_lock_task_context(task, ctxn, &flags);
         if (ctx) {
                 ++ctx->pin_count;
                 raw_spin_unlock_irqrestore(&ctx->lock, flags);
         }
         return ctx;
 }
 
 static void perf_unpin_context(struct perf_event_context *ctx)
 {
         unsigned long flags;
 
         raw_spin_lock_irqsave(&ctx->lock, flags);
         --ctx->pin_count;
         raw_spin_unlock_irqrestore(&ctx->lock, flags);
 }
 
 /*
  * Update the record of the current time in a context.
  */
 static void update_context_time(struct perf_event_context *ctx)
 {
         u64 now = perf_clock();
 
         ctx->time += now - ctx->timestamp;
         ctx->timestamp = now;
 }
 
 static u64 perf_event_time(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
 
         if (is_cgroup_event(event))
                 return perf_cgroup_event_time(event);
 
         return ctx ? ctx->time : 0;
 }
 
 /*
  * Update the total_time_enabled and total_time_running fields for a event.
  */
 static void update_event_times(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
         u64 run_end;
 
         lockdep_assert_held(&ctx->lock);
 
         if (event->state < PERF_EVENT_STATE_INACTIVE ||
             event->group_leader->state < PERF_EVENT_STATE_INACTIVE)
                 return;
 
         /*
          * in cgroup mode, time_enabled represents
          * the time the event was enabled AND active
          * tasks were in the monitored cgroup. This is
          * independent of the activity of the context as
          * there may be a mix of cgroup and non-cgroup events.
          *
          * That is why we treat cgroup events differently
          * here.
          */
         if (is_cgroup_event(event))
                 run_end = perf_cgroup_event_time(event);
         else if (ctx->is_active)
                 run_end = ctx->time;
         else
                 run_end = event->tstamp_stopped;
 
         event->total_time_enabled = run_end - event->tstamp_enabled;
 
         if (event->state == PERF_EVENT_STATE_INACTIVE)
                 run_end = event->tstamp_stopped;
         else
                 run_end = perf_event_time(event);
 
         event->total_time_running = run_end - event->tstamp_running;
 
 }
 
 /*
  * Update total_time_enabled and total_time_running for all events in a group.
  */
 static void update_group_times(struct perf_event *leader)
 {
         struct perf_event *event;
 
         update_event_times(leader);
         list_for_each_entry(event, &leader->sibling_list, group_entry)
                 update_event_times(event);
 }
 
 static struct list_head *
 ctx_group_list(struct perf_event *event, struct perf_event_context *ctx)
 {
         if (event->attr.pinned)
                 return &ctx->pinned_groups;
         else
                 return &ctx->flexible_groups;
 }
 
 /*
  * Add a event from the lists for its context.
  * Must be called with ctx->mutex and ctx->lock held.
  */
 static void
 list_add_event(struct perf_event *event, struct perf_event_context *ctx)
 {
         lockdep_assert_held(&ctx->lock);
 
         WARN_ON_ONCE(event->attach_state & PERF_ATTACH_CONTEXT);
         event->attach_state |= PERF_ATTACH_CONTEXT;
 
         /*
          * If we're a stand alone event or group leader, we go to the context
          * list, group events are kept attached to the group so that
          * perf_group_detach can, at all times, locate all siblings.
          */
         if (event->group_leader == event) {
                 struct list_head *list;
 
                 if (is_software_event(event))
                         event->group_flags |= PERF_GROUP_SOFTWARE;
 
                 list = ctx_group_list(event, ctx);
                 list_add_tail(&event->group_entry, list);
         }
 
         if (is_cgroup_event(event))
                 ctx->nr_cgroups++;
 
         list_add_rcu(&event->event_entry, &ctx->event_list);
         ctx->nr_events++;
         if (event->attr.inherit_stat)
                 ctx->nr_stat++;
 
         ctx->generation++;
 }
 
 /*
  * Initialize event state based on the perf_event_attr::disabled.
  */
 static inline void perf_event__state_init(struct perf_event *event)
 {
         event->state = event->attr.disabled ? PERF_EVENT_STATE_OFF :
                                               PERF_EVENT_STATE_INACTIVE;
 }
 
 static void __perf_event_read_size(struct perf_event *event, int nr_siblings)
 {
         int entry = sizeof(u64); /* value */
         int size = 0;
         int nr = 1;
 
         if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                 size += sizeof(u64);
 
         if (event->attr.read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                 size += sizeof(u64);
 
         if (event->attr.read_format & PERF_FORMAT_ID)
                 entry += sizeof(u64);
 
         if (event->attr.read_format & PERF_FORMAT_GROUP) {
                 nr += nr_siblings;
                 size += sizeof(u64);
         }
 
         size += entry * nr;
         event->read_size = size;
 }
 
 static void __perf_event_header_size(struct perf_event *event, u64 sample_type)
 {
         struct perf_sample_data *data;
         u16 size = 0;
 
         if (sample_type & PERF_SAMPLE_IP)
                 size += sizeof(data->ip);
 
         if (sample_type & PERF_SAMPLE_ADDR)
                 size += sizeof(data->addr);
 
         if (sample_type & PERF_SAMPLE_PERIOD)
                 size += sizeof(data->period);
 
         if (sample_type & PERF_SAMPLE_WEIGHT)
                 size += sizeof(data->weight);
 
         if (sample_type & PERF_SAMPLE_READ)
                 size += event->read_size;
 
         if (sample_type & PERF_SAMPLE_DATA_SRC)
                 size += sizeof(data->data_src.val);
 
         if (sample_type & PERF_SAMPLE_TRANSACTION)
                 size += sizeof(data->txn);
 
         event->header_size = size;
 }
 
 /*
  * Called at perf_event creation and when events are attached/detached from a
  * group.
  */
 static void perf_event__header_size(struct perf_event *event)
 {
         __perf_event_read_size(event,
                                event->group_leader->nr_siblings);
         __perf_event_header_size(event, event->attr.sample_type);
 }
 
 static void perf_event__id_header_size(struct perf_event *event)
 {
         struct perf_sample_data *data;
         u64 sample_type = event->attr.sample_type;
         u16 size = 0;
 
         if (sample_type & PERF_SAMPLE_TID)
                 size += sizeof(data->tid_entry);
 
         if (sample_type & PERF_SAMPLE_TIME)
                 size += sizeof(data->time);
 
         if (sample_type & PERF_SAMPLE_IDENTIFIER)
                 size += sizeof(data->id);
 
         if (sample_type & PERF_SAMPLE_ID)
                 size += sizeof(data->id);
 
         if (sample_type & PERF_SAMPLE_STREAM_ID)
                 size += sizeof(data->stream_id);
 
         if (sample_type & PERF_SAMPLE_CPU)
                 size += sizeof(data->cpu_entry);
 
         event->id_header_size = size;
 }
 
 static bool perf_event_validate_size(struct perf_event *event)
 {
         /*
          * The values computed here will be over-written when we actually
          * attach the event.
          */
         __perf_event_read_size(event, event->group_leader->nr_siblings + 1);
         __perf_event_header_size(event, event->attr.sample_type & ~PERF_SAMPLE_READ);
         perf_event__id_header_size(event);
 
         /*
          * Sum the lot; should not exceed the 64k limit we have on records.
          * Conservative limit to allow for callchains and other variable fields.
          */
         if (event->read_size + event->header_size +
             event->id_header_size + sizeof(struct perf_event_header) >= 16*1024)
                 return false;
 
         return true;
 }
 
 static void perf_group_attach(struct perf_event *event)
 {
         struct perf_event *group_leader = event->group_leader, *pos;
 
         /*
          * We can have double attach due to group movement in perf_event_open.
          */
         if (event->attach_state & PERF_ATTACH_GROUP)
                 return;
 
         event->attach_state |= PERF_ATTACH_GROUP;
 
         if (group_leader == event)
                 return;
 
         WARN_ON_ONCE(group_leader->ctx != event->ctx);
 
         if (group_leader->group_flags & PERF_GROUP_SOFTWARE &&
                         !is_software_event(event))
                 group_leader->group_flags &= ~PERF_GROUP_SOFTWARE;
 
         list_add_tail(&event->group_entry, &group_leader->sibling_list);
         group_leader->nr_siblings++;
 
         perf_event__header_size(group_leader);
 
         list_for_each_entry(pos, &group_leader->sibling_list, group_entry)
                 perf_event__header_size(pos);
 }
 
 /*
  * Remove a event from the lists for its context.
  * Must be called with ctx->mutex and ctx->lock held.
  */
 static void
 list_del_event(struct perf_event *event, struct perf_event_context *ctx)
 {
         struct perf_cpu_context *cpuctx;
 
         WARN_ON_ONCE(event->ctx != ctx);
         lockdep_assert_held(&ctx->lock);
 
         /*
          * We can have double detach due to exit/hot-unplug + close.
          */
         if (!(event->attach_state & PERF_ATTACH_CONTEXT))
                 return;
 
         event->attach_state &= ~PERF_ATTACH_CONTEXT;
 
         if (is_cgroup_event(event)) {
                 ctx->nr_cgroups--;
                 /*
                  * Because cgroup events are always per-cpu events, this will
                  * always be called from the right CPU.
                  */
                 cpuctx = __get_cpu_context(ctx);
                 /*
                  * If there are no more cgroup events then clear cgrp to avoid
                  * stale pointer in update_cgrp_time_from_cpuctx().
                  */
                 if (!ctx->nr_cgroups)
                         cpuctx->cgrp = NULL;
         }
 
         ctx->nr_events--;
         if (event->attr.inherit_stat)
                 ctx->nr_stat--;
 
         list_del_rcu(&event->event_entry);
 
         if (event->group_leader == event)
                 list_del_init(&event->group_entry);
 
         update_group_times(event);
 
         /*
          * If event was in error state, then keep it
          * that way, otherwise bogus counts will be
          * returned on read(). The only way to get out
          * of error state is by explicit re-enabling
          * of the event
          */
         if (event->state > PERF_EVENT_STATE_OFF)
                 event->state = PERF_EVENT_STATE_OFF;
 
         ctx->generation++;
 }
 
 static void perf_group_detach(struct perf_event *event)
 {
         struct perf_event *sibling, *tmp;
         struct list_head *list = NULL;
 
         /*
          * We can have double detach due to exit/hot-unplug + close.
          */
         if (!(event->attach_state & PERF_ATTACH_GROUP))
                 return;
 
         event->attach_state &= ~PERF_ATTACH_GROUP;
 
         /*
          * If this is a sibling, remove it from its group.
          */
         if (event->group_leader != event) {
                 list_del_init(&event->group_entry);
                 event->group_leader->nr_siblings--;
                 goto out;
         }
 
         if (!list_empty(&event->group_entry))
                 list = &event->group_entry;
 
         /*
          * If this was a group event with sibling events then
          * upgrade the siblings to singleton events by adding them
          * to whatever list we are on.
          */
         list_for_each_entry_safe(sibling, tmp, &event->sibling_list, group_entry) {
                 if (list)
                         list_move_tail(&sibling->group_entry, list);
                 sibling->group_leader = sibling;
 
                 /* Inherit group flags from the previous leader */
                 sibling->group_flags = event->group_flags;
 
                 WARN_ON_ONCE(sibling->ctx != event->ctx);
         }
 
 out:
         perf_event__header_size(event->group_leader);
 
         list_for_each_entry(tmp, &event->group_leader->sibling_list, group_entry)
                 perf_event__header_size(tmp);
 }
 
 static bool is_orphaned_event(struct perf_event *event)
 {
         return event->state == PERF_EVENT_STATE_DEAD;
 }
 
 static inline int __pmu_filter_match(struct perf_event *event)
 {
         struct pmu *pmu = event->pmu;
         return pmu->filter_match ? pmu->filter_match(event) : 1;
 }
 
 /*
  * Check whether we should attempt to schedule an event group based on
  * PMU-specific filtering. An event group can consist of HW and SW events,
  * potentially with a SW leader, so we must check all the filters, to
  * determine whether a group is schedulable:
  */
 static inline int pmu_filter_match(struct perf_event *event)
 {
         struct perf_event *child;
 
         if (!__pmu_filter_match(event))
                 return 0;
 
         list_for_each_entry(child, &event->sibling_list, group_entry) {
                 if (!__pmu_filter_match(child))
                         return 0;
         }
 
         return 1;
 }
 
 static inline int
 event_filter_match(struct perf_event *event)
 {
         return (event->cpu == -1 || event->cpu == smp_processor_id())
             && perf_cgroup_match(event) && pmu_filter_match(event);
 }
 
 static void
 event_sched_out(struct perf_event *event,
                   struct perf_cpu_context *cpuctx,
                   struct perf_event_context *ctx)
 {
         u64 tstamp = perf_event_time(event);
         u64 delta;
 
         WARN_ON_ONCE(event->ctx != ctx);
         lockdep_assert_held(&ctx->lock);
 
         /*
          * An event which could not be activated because of
          * filter mismatch still needs to have its timings
          * maintained, otherwise bogus information is return
          * via read() for time_enabled, time_running:
          */
         if (event->state == PERF_EVENT_STATE_INACTIVE
             && !event_filter_match(event)) {
                 delta = tstamp - event->tstamp_stopped;
                 event->tstamp_running += delta;
                 event->tstamp_stopped = tstamp;
         }
 
         if (event->state != PERF_EVENT_STATE_ACTIVE)
                 return;
 
         perf_pmu_disable(event->pmu);
 
         event->tstamp_stopped = tstamp;
         event->pmu->del(event, 0);
         event->oncpu = -1;
         event->state = PERF_EVENT_STATE_INACTIVE;
         if (event->pending_disable) {
                 event->pending_disable = 0;
                 event->state = PERF_EVENT_STATE_OFF;
         }
 
         if (!is_software_event(event))
                 cpuctx->active_oncpu--;
         if (!--ctx->nr_active)
                 perf_event_ctx_deactivate(ctx);
         if (event->attr.freq && event->attr.sample_freq)
                 ctx->nr_freq--;
         if (event->attr.exclusive || !cpuctx->active_oncpu)
                 cpuctx->exclusive = 0;
 
         perf_pmu_enable(event->pmu);
 }
 
 static void
 group_sched_out(struct perf_event *group_event,
                 struct perf_cpu_context *cpuctx,
                 struct perf_event_context *ctx)
 {
         struct perf_event *event;
         int state = group_event->state;
 
         event_sched_out(group_event, cpuctx, ctx);
 
         /*
          * Schedule out siblings (if any):
          */
         list_for_each_entry(event, &group_event->sibling_list, group_entry)
                 event_sched_out(event, cpuctx, ctx);
 
         if (state == PERF_EVENT_STATE_ACTIVE && group_event->attr.exclusive)
                 cpuctx->exclusive = 0;
 }
 
 #define DETACH_GROUP    0x01UL
 
 /*
  * Cross CPU call to remove a performance event
  *
  * We disable the event on the hardware level first. After that we
  * remove it from the context list.
  */
 static void
 __perf_remove_from_context(struct perf_event *event,
                            struct perf_cpu_context *cpuctx,
                            struct perf_event_context *ctx,
                            void *info)
 {
         unsigned long flags = (unsigned long)info;
 
         event_sched_out(event, cpuctx, ctx);
         if (flags & DETACH_GROUP)
                 perf_group_detach(event);
         list_del_event(event, ctx);
 
         if (!ctx->nr_events && ctx->is_active) {
                 ctx->is_active = 0;
                 if (ctx->task) {
                         WARN_ON_ONCE(cpuctx->task_ctx != ctx);
                         cpuctx->task_ctx = NULL;
                 }
         }
 }
 
 /*
  * Remove the event from a task's (or a CPU's) list of events.
  *
  * If event->ctx is a cloned context, callers must make sure that
  * every task struct that event->ctx->task could possibly point to
  * remains valid.  This is OK when called from perf_release since
  * that only calls us on the top-level context, which can't be a clone.
  * When called from perf_event_exit_task, it's OK because the
  * context has been detached from its task.
  */
 static void perf_remove_from_context(struct perf_event *event, unsigned long flags)
 {
         lockdep_assert_held(&event->ctx->mutex);
 
         event_function_call(event, __perf_remove_from_context, (void *)flags);
 }
 
 /*
  * Cross CPU call to disable a performance event
  */
 static void __perf_event_disable(struct perf_event *event,
                                  struct perf_cpu_context *cpuctx,
                                  struct perf_event_context *ctx,
                                  void *info)
 {
         if (event->state < PERF_EVENT_STATE_INACTIVE)
                 return;
 
         update_context_time(ctx);
         update_cgrp_time_from_event(event);
         update_group_times(event);
         if (event == event->group_leader)
                 group_sched_out(event, cpuctx, ctx);
         else
                 event_sched_out(event, cpuctx, ctx);
         event->state = PERF_EVENT_STATE_OFF;
 }
 
 /*
  * Disable a event.
  *
  * If event->ctx is a cloned context, callers must make sure that
  * every task struct that event->ctx->task could possibly point to
  * remains valid.  This condition is satisifed when called through
  * perf_event_for_each_child or perf_event_for_each because they
  * hold the top-level event's child_mutex, so any descendant that
  * goes to exit will block in perf_event_exit_event().
  *
  * When called from perf_pending_event it's OK because event->ctx
  * is the current context on this CPU and preemption is disabled,
  * hence we can't get into perf_event_task_sched_out for this context.
  */
 static void _perf_event_disable(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
 
         raw_spin_lock_irq(&ctx->lock);
         if (event->state <= PERF_EVENT_STATE_OFF) {
                 raw_spin_unlock_irq(&ctx->lock);
                 return;
         }
         raw_spin_unlock_irq(&ctx->lock);
 
         event_function_call(event, __perf_event_disable, NULL);
 }
 
 void perf_event_disable_local(struct perf_event *event)
 {
         event_function_local(event, __perf_event_disable, NULL);
 }
 
 /*
  * Strictly speaking kernel users cannot create groups and therefore this
  * interface does not need the perf_event_ctx_lock() magic.
  */
 void perf_event_disable(struct perf_event *event)
 {
         struct perf_event_context *ctx;
 
         ctx = perf_event_ctx_lock(event);
         _perf_event_disable(event);
         perf_event_ctx_unlock(event, ctx);
 }
 EXPORT_SYMBOL_GPL(perf_event_disable);
 
 static void perf_set_shadow_time(struct perf_event *event,
                                  struct perf_event_context *ctx,
                                  u64 tstamp)
 {
         /*
          * use the correct time source for the time snapshot
          *
          * We could get by without this by leveraging the
          * fact that to get to this function, the caller
          * has most likely already called update_context_time()
          * and update_cgrp_time_xx() and thus both timestamp
          * are identical (or very close). Given that tstamp is,
          * already adjusted for cgroup, we could say that:
          *    tstamp - ctx->timestamp
          * is equivalent to
          *    tstamp - cgrp->timestamp.
          *
          * Then, in perf_output_read(), the calculation would
          * work with no changes because:
          * - event is guaranteed scheduled in
          * - no scheduled out in between
          * - thus the timestamp would be the same
          *
          * But this is a bit hairy.
          *
          * So instead, we have an explicit cgroup call to remain
          * within the time time source all along. We believe it
          * is cleaner and simpler to understand.
          */
         if (is_cgroup_event(event))
                 perf_cgroup_set_shadow_time(event, tstamp);
         else
                 event->shadow_ctx_time = tstamp - ctx->timestamp;
 }
 
 #define MAX_INTERRUPTS (~0ULL)
 
 static void perf_log_throttle(struct perf_event *event, int enable);
 static void perf_log_itrace_start(struct perf_event *event);
 
 static int
 event_sched_in(struct perf_event *event,
                  struct perf_cpu_context *cpuctx,
                  struct perf_event_context *ctx)
 {
         u64 tstamp = perf_event_time(event);
         int ret = 0;
 
         lockdep_assert_held(&ctx->lock);
 
         if (event->state <= PERF_EVENT_STATE_OFF)
                 return 0;
 
         WRITE_ONCE(event->oncpu, smp_processor_id());
         /*
          * Order event::oncpu write to happen before the ACTIVE state
          * is visible.
          */
         smp_wmb();
         WRITE_ONCE(event->state, PERF_EVENT_STATE_ACTIVE);
 
         /*
          * Unthrottle events, since we scheduled we might have missed several
          * ticks already, also for a heavily scheduling task there is little
          * guarantee it'll get a tick in a timely manner.
          */
         if (unlikely(event->hw.interrupts == MAX_INTERRUPTS)) {
                 perf_log_throttle(event, 1);
                 event->hw.interrupts = 0;
         }
 
         /*
          * The new state must be visible before we turn it on in the hardware:
          */
         smp_wmb();
 
         perf_pmu_disable(event->pmu);
 
         perf_set_shadow_time(event, ctx, tstamp);
 
         perf_log_itrace_start(event);
 
         if (event->pmu->add(event, PERF_EF_START)) {
                 event->state = PERF_EVENT_STATE_INACTIVE;
                 event->oncpu = -1;
                 ret = -EAGAIN;
                 goto out;
         }
 
         event->tstamp_running += tstamp - event->tstamp_stopped;
 
         if (!is_software_event(event))
                 cpuctx->active_oncpu++;
         if (!ctx->nr_active++)
                 perf_event_ctx_activate(ctx);
         if (event->attr.freq && event->attr.sample_freq)
                 ctx->nr_freq++;
 
         if (event->attr.exclusive)
                 cpuctx->exclusive = 1;
 
 out:
         perf_pmu_enable(event->pmu);
 
         return ret;
 }
 
 static int
 group_sched_in(struct perf_event *group_event,
                struct perf_cpu_context *cpuctx,
                struct perf_event_context *ctx)
 {
         struct perf_event *event, *partial_group = NULL;
         struct pmu *pmu = ctx->pmu;
         u64 now = ctx->time;
         bool simulate = false;
 
         if (group_event->state == PERF_EVENT_STATE_OFF)
                 return 0;
 
         pmu->start_txn(pmu, PERF_PMU_TXN_ADD);
 
         if (event_sched_in(group_event, cpuctx, ctx)) {
                 pmu->cancel_txn(pmu);
                 perf_mux_hrtimer_restart(cpuctx);
                 return -EAGAIN;
         }
 
         /*
          * Schedule in siblings as one group (if any):
          */
         list_for_each_entry(event, &group_event->sibling_list, group_entry) {
                 if (event_sched_in(event, cpuctx, ctx)) {
                         partial_group = event;
                         goto group_error;
                 }
         }
 
         if (!pmu->commit_txn(pmu))
                 return 0;
 
 group_error:
         /*
          * Groups can be scheduled in as one unit only, so undo any
          * partial group before returning:
          * The events up to the failed event are scheduled out normally,
          * tstamp_stopped will be updated.
          *
          * The failed events and the remaining siblings need to have
          * their timings updated as if they had gone thru event_sched_in()
          * and event_sched_out(). This is required to get consistent timings
          * across the group. This also takes care of the case where the group
          * could never be scheduled by ensuring tstamp_stopped is set to mark
          * the time the event was actually stopped, such that time delta
          * calculation in update_event_times() is correct.
          */
         list_for_each_entry(event, &group_event->sibling_list, group_entry) {
                 if (event == partial_group)
                         simulate = true;
 
                 if (simulate) {
                         event->tstamp_running += now - event->tstamp_stopped;
                         event->tstamp_stopped = now;
                 } else {
                         event_sched_out(event, cpuctx, ctx);
                 }
         }
         event_sched_out(group_event, cpuctx, ctx);
 
         pmu->cancel_txn(pmu);
 
         perf_mux_hrtimer_restart(cpuctx);
 
         return -EAGAIN;
 }
 
 /*
  * Work out whether we can put this event group on the CPU now.
  */
 static int group_can_go_on(struct perf_event *event,
                            struct perf_cpu_context *cpuctx,
                            int can_add_hw)
 {
         /*
          * Groups consisting entirely of software events can always go on.
          */
         if (event->group_flags & PERF_GROUP_SOFTWARE)
                 return 1;
         /*
          * If an exclusive group is already on, no other hardware
          * events can go on.
          */
         if (cpuctx->exclusive)
                 return 0;
         /*
          * If this group is exclusive and there are already
          * events on the CPU, it can't go on.
          */
         if (event->attr.exclusive && cpuctx->active_oncpu)
                 return 0;
         /*
          * Otherwise, try to add it if all previous groups were able
          * to go on.
          */
         return can_add_hw;
 }
 
 static void add_event_to_ctx(struct perf_event *event,
                                struct perf_event_context *ctx)
 {
         u64 tstamp = perf_event_time(event);
 
         list_add_event(event, ctx);
         perf_group_attach(event);
         event->tstamp_enabled = tstamp;
         event->tstamp_running = tstamp;
         event->tstamp_stopped = tstamp;
 }
 
 static void ctx_sched_out(struct perf_event_context *ctx,
                           struct perf_cpu_context *cpuctx,
                           enum event_type_t event_type);
 static void
 ctx_sched_in(struct perf_event_context *ctx,
              struct perf_cpu_context *cpuctx,
              enum event_type_t event_type,
              struct task_struct *task);
 
 static void task_ctx_sched_out(struct perf_cpu_context *cpuctx,
                                struct perf_event_context *ctx)
 {
         if (!cpuctx->task_ctx)
                 return;
 
         if (WARN_ON_ONCE(ctx != cpuctx->task_ctx))
                 return;
 
         ctx_sched_out(ctx, cpuctx, EVENT_ALL);
 }
 
 static void perf_event_sched_in(struct perf_cpu_context *cpuctx,
                                 struct perf_event_context *ctx,
                                 struct task_struct *task)
 {
         cpu_ctx_sched_in(cpuctx, EVENT_PINNED, task);
         if (ctx)
                 ctx_sched_in(ctx, cpuctx, EVENT_PINNED, task);
         cpu_ctx_sched_in(cpuctx, EVENT_FLEXIBLE, task);
         if (ctx)
                 ctx_sched_in(ctx, cpuctx, EVENT_FLEXIBLE, task);
 }
 
 static void ctx_resched(struct perf_cpu_context *cpuctx,
                         struct perf_event_context *task_ctx)
 {
         perf_pmu_disable(cpuctx->ctx.pmu);
         if (task_ctx)
                 task_ctx_sched_out(cpuctx, task_ctx);
         cpu_ctx_sched_out(cpuctx, EVENT_ALL);
         perf_event_sched_in(cpuctx, task_ctx, current);
         perf_pmu_enable(cpuctx->ctx.pmu);
 }
 
 /*
  * Cross CPU call to install and enable a performance event
  *
  * Very similar to remote_function() + event_function() but cannot assume that
  * things like ctx->is_active and cpuctx->task_ctx are set.
  */
 static int  __perf_install_in_context(void *info)
 {
         struct perf_event *event = info;
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
         struct perf_event_context *task_ctx = cpuctx->task_ctx;
         bool activate = true;
         int ret = 0;
 
         raw_spin_lock(&cpuctx->ctx.lock);
         if (ctx->task) {
                 raw_spin_lock(&ctx->lock);
                 task_ctx = ctx;
 
                 /* If we're on the wrong CPU, try again */
                 if (task_cpu(ctx->task) != smp_processor_id()) {
                         ret = -ESRCH;
                         goto unlock;
                 }
 
                 /*
                  * If we're on the right CPU, see if the task we target is
                  * current, if not we don't have to activate the ctx, a future
                  * context switch will do that for us.
                  */
                 if (ctx->task != current)
                         activate = false;
                 else
                         WARN_ON_ONCE(cpuctx->task_ctx && cpuctx->task_ctx != ctx);
 
         } else if (task_ctx) {
                 raw_spin_lock(&task_ctx->lock);
         }
 
         if (activate) {
                 ctx_sched_out(ctx, cpuctx, EVENT_TIME);
                 add_event_to_ctx(event, ctx);
                 ctx_resched(cpuctx, task_ctx);
         } else {
                 add_event_to_ctx(event, ctx);
         }
 
 unlock:
         perf_ctx_unlock(cpuctx, task_ctx);
 
         return ret;
 }
 
 /*
  * Attach a performance event to a context.
  *
  * Very similar to event_function_call, see comment there.
  */
 static void
 perf_install_in_context(struct perf_event_context *ctx,
                         struct perf_event *event,
                         int cpu)
 {
         struct task_struct *task = READ_ONCE(ctx->task);
 
         lockdep_assert_held(&ctx->mutex);
 
         event->ctx = ctx;
         if (event->cpu != -1)
                 event->cpu = cpu;
 
         if (!task) {
                 cpu_function_call(cpu, __perf_install_in_context, event);
                 return;
         }
 
         /*
          * Should not happen, we validate the ctx is still alive before calling.
          */
         if (WARN_ON_ONCE(task == TASK_TOMBSTONE))
                 return;
 
         /*
          * Installing events is tricky because we cannot rely on ctx->is_active
          * to be set in case this is the nr_events 0 -> 1 transition.
          */
 again:
         /*
          * Cannot use task_function_call() because we need to run on the task's
          * CPU regardless of whether its current or not.
          */
         if (!cpu_function_call(task_cpu(task), __perf_install_in_context, event))
                 return;
 
         raw_spin_lock_irq(&ctx->lock);
         task = ctx->task;
         if (WARN_ON_ONCE(task == TASK_TOMBSTONE)) {
                 /*
                  * Cannot happen because we already checked above (which also
                  * cannot happen), and we hold ctx->mutex, which serializes us
                  * against perf_event_exit_task_context().
                  */
                 raw_spin_unlock_irq(&ctx->lock);
                 return;
         }
         raw_spin_unlock_irq(&ctx->lock);
         /*
          * Since !ctx->is_active doesn't mean anything, we must IPI
          * unconditionally.
          */
         goto again;
 }
 
 /*
  * Put a event into inactive state and update time fields.
  * Enabling the leader of a group effectively enables all
  * the group members that aren't explicitly disabled, so we
  * have to update their ->tstamp_enabled also.
  * Note: this works for group members as well as group leaders
  * since the non-leader members' sibling_lists will be empty.
  */
 static void __perf_event_mark_enabled(struct perf_event *event)
 {
         struct perf_event *sub;
         u64 tstamp = perf_event_time(event);
 
         event->state = PERF_EVENT_STATE_INACTIVE;
         event->tstamp_enabled = tstamp - event->total_time_enabled;
         list_for_each_entry(sub, &event->sibling_list, group_entry) {
                 if (sub->state >= PERF_EVENT_STATE_INACTIVE)
                         sub->tstamp_enabled = tstamp - sub->total_time_enabled;
         }
 }
 
 /*
  * Cross CPU call to enable a performance event
  */
 static void __perf_event_enable(struct perf_event *event,
                                 struct perf_cpu_context *cpuctx,
                                 struct perf_event_context *ctx,
                                 void *info)
 {
         struct perf_event *leader = event->group_leader;
         struct perf_event_context *task_ctx;
 
         if (event->state >= PERF_EVENT_STATE_INACTIVE ||
             event->state <= PERF_EVENT_STATE_ERROR)
                 return;
 
         if (ctx->is_active)
                 ctx_sched_out(ctx, cpuctx, EVENT_TIME);
 
         __perf_event_mark_enabled(event);
 
         if (!ctx->is_active)
                 return;
 
         if (!event_filter_match(event)) {
                 if (is_cgroup_event(event))
                         perf_cgroup_defer_enabled(event);
                 ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
                 return;
         }
 
         /*
          * If the event is in a group and isn't the group leader,
          * then don't put it on unless the group is on.
          */
         if (leader != event && leader->state != PERF_EVENT_STATE_ACTIVE) {
                 ctx_sched_in(ctx, cpuctx, EVENT_TIME, current);
                 return;
         }
 
         task_ctx = cpuctx->task_ctx;
         if (ctx->task)
                 WARN_ON_ONCE(task_ctx != ctx);
 
         ctx_resched(cpuctx, task_ctx);
 }
 
 /*
  * Enable a event.
  *
  * If event->ctx is a cloned context, callers must make sure that
  * every task struct that event->ctx->task could possibly point to
  * remains valid.  This condition is satisfied when called through
  * perf_event_for_each_child or perf_event_for_each as described
  * for perf_event_disable.
  */
 static void _perf_event_enable(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
 
         raw_spin_lock_irq(&ctx->lock);
         if (event->state >= PERF_EVENT_STATE_INACTIVE ||
             event->state <  PERF_EVENT_STATE_ERROR) {
                 raw_spin_unlock_irq(&ctx->lock);
                 return;
         }
 
         /*
          * If the event is in error state, clear that first.
          *
          * That way, if we see the event in error state below, we know that it
          * has gone back into error state, as distinct from the task having
          * been scheduled away before the cross-call arrived.
          */
         if (event->state == PERF_EVENT_STATE_ERROR)
                 event->state = PERF_EVENT_STATE_OFF;
         raw_spin_unlock_irq(&ctx->lock);
 
         event_function_call(event, __perf_event_enable, NULL);
 }
 
 /*
  * See perf_event_disable();
  */
 void perf_event_enable(struct perf_event *event)
 {
         struct perf_event_context *ctx;
 
         ctx = perf_event_ctx_lock(event);
         _perf_event_enable(event);
         perf_event_ctx_unlock(event, ctx);
 }
 EXPORT_SYMBOL_GPL(perf_event_enable);
 
 struct stop_event_data {
         struct perf_event       *event;
         unsigned int            restart;
 };
 
 static int __perf_event_stop(void *info)
 {
         struct stop_event_data *sd = info;
         struct perf_event *event = sd->event;
 
         /* if it's already INACTIVE, do nothing */
         if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
                 return 0;
 
         /* matches smp_wmb() in event_sched_in() */
         smp_rmb();
 
         /*
          * There is a window with interrupts enabled before we get here,
          * so we need to check again lest we try to stop another CPU's event.
          */
         if (READ_ONCE(event->oncpu) != smp_processor_id())
                 return -EAGAIN;
 
         event->pmu->stop(event, PERF_EF_UPDATE);
 
         /*
          * May race with the actual stop (through perf_pmu_output_stop()),
          * but it is only used for events with AUX ring buffer, and such
          * events will refuse to restart because of rb::aux_mmap_count==0,
          * see comments in perf_aux_output_begin().
          *
          * Since this is happening on a event-local CPU, no trace is lost
          * while restarting.
          */
         if (sd->restart)
                 event->pmu->start(event, PERF_EF_START);
 
         return 0;
 }
 
 static int perf_event_restart(struct perf_event *event)
 {
         struct stop_event_data sd = {
                 .event          = event,
                 .restart        = 1,
         };
         int ret = 0;
 
         do {
                 if (READ_ONCE(event->state) != PERF_EVENT_STATE_ACTIVE)
                         return 0;
 
                 /* matches smp_wmb() in event_sched_in() */
                 smp_rmb();
 
                 /*
                  * We only want to restart ACTIVE events, so if the event goes
                  * inactive here (event->oncpu==-1), there's nothing more to do;
                  * fall through with ret==-ENXIO.
                  */
                 ret = cpu_function_call(READ_ONCE(event->oncpu),
                                         __perf_event_stop, &sd);
         } while (ret == -EAGAIN);
 
         return ret;
 }
 
 /*
  * In order to contain the amount of racy and tricky in the address filter
  * configuration management, it is a two part process:
  *
  * (p1) when userspace mappings change as a result of (1) or (2) or (3) below,
  *      we update the addresses of corresponding vmas in
  *      event::addr_filters_offs array and bump the event::addr_filters_gen;
  * (p2) when an event is scheduled in (pmu::add), it calls
  *      perf_event_addr_filters_sync() which calls pmu::addr_filters_sync()
  *      if the generation has changed since the previous call.
  *
  * If (p1) happens while the event is active, we restart it to force (p2).
  *
  * (1) perf_addr_filters_apply(): adjusting filters' offsets based on
  *     pre-existing mappings, called once when new filters arrive via SET_FILTER
  *     ioctl;
  * (2) perf_addr_filters_adjust(): adjusting filters' offsets based on newly
  *     registered mapping, called for every new mmap(), with mm::mmap_sem down
  *     for reading;
  * (3) perf_event_addr_filters_exec(): clearing filters' offsets in the process
  *     of exec.
  */
 void perf_event_addr_filters_sync(struct perf_event *event)
 {
         struct perf_addr_filters_head *ifh = perf_event_addr_filters(event);
 
         if (!has_addr_filter(event))
                 return;
 
         raw_spin_lock(&ifh->lock);
         if (event->addr_filters_gen != event->hw.addr_filters_gen) {
                 event->pmu->addr_filters_sync(event);
                 event->hw.addr_filters_gen = event->addr_filters_gen;
         }
         raw_spin_unlock(&ifh->lock);
 }
 EXPORT_SYMBOL_GPL(perf_event_addr_filters_sync);
 
 static int _perf_event_refresh(struct perf_event *event, int refresh)
 {
         /*
          * not supported on inherited events
          */
         if (event->attr.inherit || !is_sampling_event(event))
                 return -EINVAL;
 
         atomic_add(refresh, &event->event_limit);
         _perf_event_enable(event);
 
         return 0;
 }
 
 /*
  * See perf_event_disable()
  */
 int perf_event_refresh(struct perf_event *event, int refresh)
 {
         struct perf_event_context *ctx;
         int ret;
 
         ctx = perf_event_ctx_lock(event);
         ret = _perf_event_refresh(event, refresh);
         perf_event_ctx_unlock(event, ctx);
 
         return ret;
 }
 EXPORT_SYMBOL_GPL(perf_event_refresh);
 
 static void ctx_sched_out(struct perf_event_context *ctx,
                           struct perf_cpu_context *cpuctx,
                           enum event_type_t event_type)
 {
         int is_active = ctx->is_active;
         struct perf_event *event;
 
         lockdep_assert_held(&ctx->lock);
 
         if (likely(!ctx->nr_events)) {
                 /*
                  * See __perf_remove_from_context().
                  */
                 WARN_ON_ONCE(ctx->is_active);
                 if (ctx->task)
                         WARN_ON_ONCE(cpuctx->task_ctx);
                 return;
         }
 
         ctx->is_active &= ~event_type;
         if (!(ctx->is_active & EVENT_ALL))
                 ctx->is_active = 0;
 
         if (ctx->task) {
                 WARN_ON_ONCE(cpuctx->task_ctx != ctx);
                 if (!ctx->is_active)
                         cpuctx->task_ctx = NULL;
         }
 
         /*
          * Always update time if it was set; not only when it changes.
          * Otherwise we can 'forget' to update time for any but the last
          * context we sched out. For example:
          *
          *   ctx_sched_out(.event_type = EVENT_FLEXIBLE)
          *   ctx_sched_out(.event_type = EVENT_PINNED)
          *
          * would only update time for the pinned events.
          */
         if (is_active & EVENT_TIME) {
                 /* update (and stop) ctx time */
                 update_context_time(ctx);
                 update_cgrp_time_from_cpuctx(cpuctx);
         }
 
         is_active ^= ctx->is_active; /* changed bits */
 
         if (!ctx->nr_active || !(is_active & EVENT_ALL))
                 return;
 
         perf_pmu_disable(ctx->pmu);
         if (is_active & EVENT_PINNED) {
                 list_for_each_entry(event, &ctx->pinned_groups, group_entry)
                         group_sched_out(event, cpuctx, ctx);
         }
 
         if (is_active & EVENT_FLEXIBLE) {
                 list_for_each_entry(event, &ctx->flexible_groups, group_entry)
                         group_sched_out(event, cpuctx, ctx);
         }
         perf_pmu_enable(ctx->pmu);
 }
 
 /*
  * Test whether two contexts are equivalent, i.e. whether they have both been
  * cloned from the same version of the same context.
  *
  * Equivalence is measured using a generation number in the context that is
  * incremented on each modification to it; see unclone_ctx(), list_add_event()
  * and list_del_event().
  */
 static int context_equiv(struct perf_event_context *ctx1,
                          struct perf_event_context *ctx2)
 {
         lockdep_assert_held(&ctx1->lock);
         lockdep_assert_held(&ctx2->lock);
 
         /* Pinning disables the swap optimization */
         if (ctx1->pin_count || ctx2->pin_count)
                 return 0;
 
         /* If ctx1 is the parent of ctx2 */
         if (ctx1 == ctx2->parent_ctx && ctx1->generation == ctx2->parent_gen)
                 return 1;
 
         /* If ctx2 is the parent of ctx1 */
         if (ctx1->parent_ctx == ctx2 && ctx1->parent_gen == ctx2->generation)
                 return 1;
 
         /*
          * If ctx1 and ctx2 have the same parent; we flatten the parent
          * hierarchy, see perf_event_init_context().
          */
         if (ctx1->parent_ctx && ctx1->parent_ctx == ctx2->parent_ctx &&
                         ctx1->parent_gen == ctx2->parent_gen)
                 return 1;
 
         /* Unmatched */
         return 0;
 }
 
 static void __perf_event_sync_stat(struct perf_event *event,
                                      struct perf_event *next_event)
 {
         u64 value;
 
         if (!event->attr.inherit_stat)
                 return;
 
         /*
          * Update the event value, we cannot use perf_event_read()
          * because we're in the middle of a context switch and have IRQs
          * disabled, which upsets smp_call_function_single(), however
          * we know the event must be on the current CPU, therefore we
          * don't need to use it.
          */
         switch (event->state) {
         case PERF_EVENT_STATE_ACTIVE:
                 event->pmu->read(event);
                 /* fall-through */
 
         case PERF_EVENT_STATE_INACTIVE:
                 update_event_times(event);
                 break;
 
         default:
                 break;
         }
 
         /*
          * In order to keep per-task stats reliable we need to flip the event
          * values when we flip the contexts.
          */
         value = local64_read(&next_event->count);
         value = local64_xchg(&event->count, value);
         local64_set(&next_event->count, value);
 
         swap(event->total_time_enabled, next_event->total_time_enabled);
         swap(event->total_time_running, next_event->total_time_running);
 
         /*
          * Since we swizzled the values, update the user visible data too.
          */
         perf_event_update_userpage(event);
         perf_event_update_userpage(next_event);
 }
 
 static void perf_event_sync_stat(struct perf_event_context *ctx,
                                    struct perf_event_context *next_ctx)
 {
         struct perf_event *event, *next_event;
 
         if (!ctx->nr_stat)
                 return;
 
         update_context_time(ctx);
 
         event = list_first_entry(&ctx->event_list,
                                    struct perf_event, event_entry);
 
         next_event = list_first_entry(&next_ctx->event_list,
                                         struct perf_event, event_entry);
 
         while (&event->event_entry != &ctx->event_list &&
                &next_event->event_entry != &next_ctx->event_list) {
 
                 __perf_event_sync_stat(event, next_event);
 
                 event = list_next_entry(event, event_entry);
                 next_event = list_next_entry(next_event, event_entry);
         }
 }
 
 static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
                                          struct task_struct *next)
 {
         struct perf_event_context *ctx = task->perf_event_ctxp[ctxn];
         struct perf_event_context *next_ctx;
         struct perf_event_context *parent, *next_parent;
         struct perf_cpu_context *cpuctx;
         int do_switch = 1;
 
         if (likely(!ctx))
                 return;
 
         cpuctx = __get_cpu_context(ctx);
         if (!cpuctx->task_ctx)
                 return;
 
         rcu_read_lock();
         next_ctx = next->perf_event_ctxp[ctxn];
         if (!next_ctx)
                 goto unlock;
 
         parent = rcu_dereference(ctx->parent_ctx);
         next_parent = rcu_dereference(next_ctx->parent_ctx);
 
         /* If neither context have a parent context; they cannot be clones. */
         if (!parent && !next_parent)
                 goto unlock;
 
         if (next_parent == ctx || next_ctx == parent || next_parent == parent) {
                 /*
                  * Looks like the two contexts are clones, so we might be
                  * able to optimize the context switch.  We lock both
                  * contexts and check that they are clones under the
                  * lock (including re-checking that neither has been
                  * uncloned in the meantime).  It doesn't matter which
                  * order we take the locks because no other cpu could
                  * be trying to lock both of these tasks.
                  */
                 raw_spin_lock(&ctx->lock);
                 raw_spin_lock_nested(&next_ctx->lock, SINGLE_DEPTH_NESTING);
                 if (context_equiv(ctx, next_ctx)) {
                         WRITE_ONCE(ctx->task, next);
                         WRITE_ONCE(next_ctx->task, task);
 
                         swap(ctx->task_ctx_data, next_ctx->task_ctx_data);
 
                         /*
                          * RCU_INIT_POINTER here is safe because we've not
                          * modified the ctx and the above modification of
                          * ctx->task and ctx->task_ctx_data are immaterial
                          * since those values are always verified under
                          * ctx->lock which we're now holding.
                          */
                         RCU_INIT_POINTER(task->perf_event_ctxp[ctxn], next_ctx);
                         RCU_INIT_POINTER(next->perf_event_ctxp[ctxn], ctx);
 
                         do_switch = 0;
 
                         perf_event_sync_stat(ctx, next_ctx);
                 }
                 raw_spin_unlock(&next_ctx->lock);
                 raw_spin_unlock(&ctx->lock);
         }
 unlock:
         rcu_read_unlock();
 
         if (do_switch) {
                 raw_spin_lock(&ctx->lock);
                 task_ctx_sched_out(cpuctx, ctx);
                 raw_spin_unlock(&ctx->lock);
         }
 }
 
 void perf_sched_cb_dec(struct pmu *pmu)
 {
         this_cpu_dec(perf_sched_cb_usages);
 }
 
 void perf_sched_cb_inc(struct pmu *pmu)
 {
         this_cpu_inc(perf_sched_cb_usages);
 }
 
 /*
  * This function provides the context switch callback to the lower code
  * layer. It is invoked ONLY when the context switch callback is enabled.
  */
 static void perf_pmu_sched_task(struct task_struct *prev,
                                 struct task_struct *next,
                                 bool sched_in)
 {
         struct perf_cpu_context *cpuctx;
         struct pmu *pmu;
         unsigned long flags;
 
         if (prev == next)
                 return;
 
         local_irq_save(flags);
 
         rcu_read_lock();
 
         list_for_each_entry_rcu(pmu, &pmus, entry) {
                 if (pmu->sched_task) {
                         cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
 
                         perf_ctx_lock(cpuctx, cpuctx->task_ctx);
 
                         perf_pmu_disable(pmu);
 
                         pmu->sched_task(cpuctx->task_ctx, sched_in);
 
                         perf_pmu_enable(pmu);
 
                         perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
                 }
         }
 
         rcu_read_unlock();
 
         local_irq_restore(flags);
 }
 
 static void perf_event_switch(struct task_struct *task,
                               struct task_struct *next_prev, bool sched_in);
 
 #define for_each_task_context_nr(ctxn)                                  \
         for ((ctxn) = 0; (ctxn) < perf_nr_task_contexts; (ctxn)++)
 
 /*
  * Called from scheduler to remove the events of the current task,
  * with interrupts disabled.
  *
  * We stop each event and update the event value in event->count.
  *
  * This does not protect us against NMI, but disable()
  * sets the disabled bit in the control field of event _before_
  * accessing the event control register. If a NMI hits, then it will
  * not restart the event.
  */
 void __perf_event_task_sched_out(struct task_struct *task,
                                  struct task_struct *next)
 {
         int ctxn;
 
         if (__this_cpu_read(perf_sched_cb_usages))
                 perf_pmu_sched_task(task, next, false);
 
         if (atomic_read(&nr_switch_events))
                 perf_event_switch(task, next, false);
 
         for_each_task_context_nr(ctxn)
                 perf_event_context_sched_out(task, ctxn, next);
 
         /*
          * if cgroup events exist on this CPU, then we need
          * to check if we have to switch out PMU state.
          * cgroup event are system-wide mode only
          */
         if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
                 perf_cgroup_sched_out(task, next);
 }
 
 /*
  * Called with IRQs disabled
  */
 static void cpu_ctx_sched_out(struct perf_cpu_context *cpuctx,
                               enum event_type_t event_type)
 {
         ctx_sched_out(&cpuctx->ctx, cpuctx, event_type);
 }
 
 static void
 ctx_pinned_sched_in(struct perf_event_context *ctx,
                     struct perf_cpu_context *cpuctx)
 {
         struct perf_event *event;
 
         list_for_each_entry(event, &ctx->pinned_groups, group_entry) {
                 if (event->state <= PERF_EVENT_STATE_OFF)
                         continue;
                 if (!event_filter_match(event))
                         continue;
 
                 /* may need to reset tstamp_enabled */
                 if (is_cgroup_event(event))
                         perf_cgroup_mark_enabled(event, ctx);
 
                 if (group_can_go_on(event, cpuctx, 1))
                         group_sched_in(event, cpuctx, ctx);
 
                 /*
                  * If this pinned group hasn't been scheduled,
                  * put it in error state.
                  */
                 if (event->state == PERF_EVENT_STATE_INACTIVE) {
                         update_group_times(event);
                         event->state = PERF_EVENT_STATE_ERROR;
                 }
         }
 }
 
 static void
 ctx_flexible_sched_in(struct perf_event_context *ctx,
                       struct perf_cpu_context *cpuctx)
 {
         struct perf_event *event;
         int can_add_hw = 1;
 
         list_for_each_entry(event, &ctx->flexible_groups, group_entry) {
                 /* Ignore events in OFF or ERROR state */
                 if (event->state <= PERF_EVENT_STATE_OFF)
                         continue;
                 /*
                  * Listen to the 'cpu' scheduling filter constraint
                  * of events:
                  */
                 if (!event_filter_match(event))
                         continue;
 
                 /* may need to reset tstamp_enabled */
                 if (is_cgroup_event(event))
                         perf_cgroup_mark_enabled(event, ctx);
 
                 if (group_can_go_on(event, cpuctx, can_add_hw)) {
                         if (group_sched_in(event, cpuctx, ctx))
                                 can_add_hw = 0;
                 }
         }
 }
 
 static void
 ctx_sched_in(struct perf_event_context *ctx,
              struct perf_cpu_context *cpuctx,
              enum event_type_t event_type,
              struct task_struct *task)
 {
         int is_active = ctx->is_active;
         u64 now;
 
         lockdep_assert_held(&ctx->lock);
 
         if (likely(!ctx->nr_events))
                 return;
 
         ctx->is_active |= (event_type | EVENT_TIME);
         if (ctx->task) {
                 if (!is_active)
                         cpuctx->task_ctx = ctx;
                 else
                         WARN_ON_ONCE(cpuctx->task_ctx != ctx);
         }
 
         is_active ^= ctx->is_active; /* changed bits */
 
         if (is_active & EVENT_TIME) {
                 /* start ctx time */
                 now = perf_clock();
                 ctx->timestamp = now;
                 perf_cgroup_set_timestamp(task, ctx);
         }
 
         /*
          * First go through the list and put on any pinned groups
          * in order to give them the best chance of going on.
          */
         if (is_active & EVENT_PINNED)
                 ctx_pinned_sched_in(ctx, cpuctx);
 
         /* Then walk through the lower prio flexible groups */
         if (is_active & EVENT_FLEXIBLE)
                 ctx_flexible_sched_in(ctx, cpuctx);
 }
 
 static void cpu_ctx_sched_in(struct perf_cpu_context *cpuctx,
                              enum event_type_t event_type,
                              struct task_struct *task)
 {
         struct perf_event_context *ctx = &cpuctx->ctx;
 
         ctx_sched_in(ctx, cpuctx, event_type, task);
 }
 
 static void perf_event_context_sched_in(struct perf_event_context *ctx,
                                         struct task_struct *task)
 {
         struct perf_cpu_context *cpuctx;
 
         cpuctx = __get_cpu_context(ctx);
         if (cpuctx->task_ctx == ctx)
                 return;
 
         perf_ctx_lock(cpuctx, ctx);
         perf_pmu_disable(ctx->pmu);
         /*
          * We want to keep the following priority order:
          * cpu pinned (that don't need to move), task pinned,
          * cpu flexible, task flexible.
          */
         cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
         perf_event_sched_in(cpuctx, ctx, task);
         perf_pmu_enable(ctx->pmu);
         perf_ctx_unlock(cpuctx, ctx);
 }
 
 /*
  * Called from scheduler to add the events of the current task
  * with interrupts disabled.
  *
  * We restore the event value and then enable it.
  *
  * This does not protect us against NMI, but enable()
  * sets the enabled bit in the control field of event _before_
  * accessing the event control register. If a NMI hits, then it will
  * keep the event running.
  */
 void __perf_event_task_sched_in(struct task_struct *prev,
                                 struct task_struct *task)
 {
         struct perf_event_context *ctx;
         int ctxn;
 
         /*
          * If cgroup events exist on this CPU, then we need to check if we have
          * to switch in PMU state; cgroup event are system-wide mode only.
          *
          * Since cgroup events are CPU events, we must schedule these in before
          * we schedule in the task events.
          */
         if (atomic_read(this_cpu_ptr(&perf_cgroup_events)))
                 perf_cgroup_sched_in(prev, task);
 
         for_each_task_context_nr(ctxn) {
                 ctx = task->perf_event_ctxp[ctxn];
                 if (likely(!ctx))
                         continue;
 
                 perf_event_context_sched_in(ctx, task);
         }
 
         if (atomic_read(&nr_switch_events))
                 perf_event_switch(task, prev, true);
 
         if (__this_cpu_read(perf_sched_cb_usages))
                 perf_pmu_sched_task(prev, task, true);
 }
 
 static u64 perf_calculate_period(struct perf_event *event, u64 nsec, u64 count)
 {
         u64 frequency = event->attr.sample_freq;
         u64 sec = NSEC_PER_SEC;
         u64 divisor, dividend;
 
         int count_fls, nsec_fls, frequency_fls, sec_fls;
 
         count_fls = fls64(count);
         nsec_fls = fls64(nsec);
         frequency_fls = fls64(frequency);
         sec_fls = 30;
 
         /*
          * We got @count in @nsec, with a target of sample_freq HZ
          * the target period becomes:
          *
          *             @count * 10^9
          * period = -------------------
          *          @nsec * sample_freq
          *
          */
 
         /*
          * Reduce accuracy by one bit such that @a and @b converge
          * to a similar magnitude.
          */
 #define REDUCE_FLS(a, b)                \
 do {                                    \
         if (a##_fls > b##_fls) {        \
                 a >>= 1;                \
                 a##_fls--;              \
         } else {                        \
                 b >>= 1;                \
                 b##_fls--;              \
         }                               \
 } while (0)
 
         /*
          * Reduce accuracy until either term fits in a u64, then proceed with
          * the other, so that finally we can do a u64/u64 division.
          */
         while (count_fls + sec_fls > 64 && nsec_fls + frequency_fls > 64) {
                 REDUCE_FLS(nsec, frequency);
                 REDUCE_FLS(sec, count);
         }
 
         if (count_fls + sec_fls > 64) {
                 divisor = nsec * frequency;
 
                 while (count_fls + sec_fls > 64) {
                         REDUCE_FLS(count, sec);
                         divisor >>= 1;
                 }
 
                 dividend = count * sec;
         } else {
                 dividend = count * sec;
 
                 while (nsec_fls + frequency_fls > 64) {
                         REDUCE_FLS(nsec, frequency);
                         dividend >>= 1;
                 }
 
                 divisor = nsec * frequency;
         }
 
         if (!divisor)
                 return dividend;
 
         return div64_u64(dividend, divisor);
 }
 
 static DEFINE_PER_CPU(int, perf_throttled_count);
 static DEFINE_PER_CPU(u64, perf_throttled_seq);
 
 static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count, bool disable)
 {
         struct hw_perf_event *hwc = &event->hw;
         s64 period, sample_period;
         s64 delta;
 
         period = perf_calculate_period(event, nsec, count);
 
         delta = (s64)(period - hwc->sample_period);
         delta = (delta + 7) / 8; /* low pass filter */
 
         sample_period = hwc->sample_period + delta;
 
         if (!sample_period)
                 sample_period = 1;
 
         hwc->sample_period = sample_period;
 
         if (local64_read(&hwc->period_left) > 8*sample_period) {
                 if (disable)
                         event->pmu->stop(event, PERF_EF_UPDATE);
 
                 local64_set(&hwc->period_left, 0);
 
                 if (disable)
                         event->pmu->start(event, PERF_EF_RELOAD);
         }
 }
 
 /*
  * combine freq adjustment with unthrottling to avoid two passes over the
  * events. At the same time, make sure, having freq events does not change
  * the rate of unthrottling as that would introduce bias.
  */
 static void perf_adjust_freq_unthr_context(struct perf_event_context *ctx,
                                            int needs_unthr)
 {
         struct perf_event *event;
         struct hw_perf_event *hwc;
         u64 now, period = TICK_NSEC;
         s64 delta;
 
         /*
          * only need to iterate over all events iff:
          * - context have events in frequency mode (needs freq adjust)
          * - there are events to unthrottle on this cpu
          */
         if (!(ctx->nr_freq || needs_unthr))
                 return;
 
         raw_spin_lock(&ctx->lock);
         perf_pmu_disable(ctx->pmu);
 
         list_for_each_entry_rcu(event, &ctx->event_list, event_entry) {
                 if (event->state != PERF_EVENT_STATE_ACTIVE)
                         continue;
 
                 if (!event_filter_match(event))
                         continue;
 
                 perf_pmu_disable(event->pmu);
 
                 hwc = &event->hw;
 
                 if (hwc->interrupts == MAX_INTERRUPTS) {
                         hwc->interrupts = 0;
                         perf_log_throttle(event, 1);
                         event->pmu->start(event, 0);
                 }
 
                 if (!event->attr.freq || !event->attr.sample_freq)
                         goto next;
 
                 /*
                  * stop the event and update event->count
                  */
                 event->pmu->stop(event, PERF_EF_UPDATE);
 
                 now = local64_read(&event->count);
                 delta = now - hwc->freq_count_stamp;
                 hwc->freq_count_stamp = now;
 
                 /*
                  * restart the event
                  * reload only if value has changed
                  * we have stopped the event so tell that
                  * to perf_adjust_period() to avoid stopping it
                  * twice.
                  */
                 if (delta > 0)
                         perf_adjust_period(event, period, delta, false);
 
                 event->pmu->start(event, delta > 0 ? PERF_EF_RELOAD : 0);
         next:
                 perf_pmu_enable(event->pmu);
         }
 
         perf_pmu_enable(ctx->pmu);
         raw_spin_unlock(&ctx->lock);
 }
 
 /*
  * Round-robin a context's events:
  */
 static void rotate_ctx(struct perf_event_context *ctx)
 {
         /*
          * Rotate the first entry last of non-pinned groups. Rotation might be
          * disabled by the inheritance code.
          */
         if (!ctx->rotate_disable)
                 list_rotate_left(&ctx->flexible_groups);
 }
 
 static int perf_rotate_context(struct perf_cpu_context *cpuctx)
 {
         struct perf_event_context *ctx = NULL;
         int rotate = 0;
 
         if (cpuctx->ctx.nr_events) {
                 if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active)
                         rotate = 1;
         }
 
         ctx = cpuctx->task_ctx;
         if (ctx && ctx->nr_events) {
                 if (ctx->nr_events != ctx->nr_active)
                         rotate = 1;
         }
 
         if (!rotate)
                 goto done;
 
         perf_ctx_lock(cpuctx, cpuctx->task_ctx);
         perf_pmu_disable(cpuctx->ctx.pmu);
 
         cpu_ctx_sched_out(cpuctx, EVENT_FLEXIBLE);
         if (ctx)
                 ctx_sched_out(ctx, cpuctx, EVENT_FLEXIBLE);
 
         rotate_ctx(&cpuctx->ctx);
         if (ctx)
                 rotate_ctx(ctx);
 
         perf_event_sched_in(cpuctx, ctx, current);
 
         perf_pmu_enable(cpuctx->ctx.pmu);
         perf_ctx_unlock(cpuctx, cpuctx->task_ctx);
 done:
 
         return rotate;
 }
 
 void perf_event_task_tick(void)
 {
         struct list_head *head = this_cpu_ptr(&active_ctx_list);
         struct perf_event_context *ctx, *tmp;
         int throttled;
 
         WARN_ON(!irqs_disabled());
 
         __this_cpu_inc(perf_throttled_seq);
         throttled = __this_cpu_xchg(perf_throttled_count, 0);
         tick_dep_clear_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS);
 
         list_for_each_entry_safe(ctx, tmp, head, active_ctx_list)
                 perf_adjust_freq_unthr_context(ctx, throttled);
 }
 
 static int event_enable_on_exec(struct perf_event *event,
                                 struct perf_event_context *ctx)
 {
         if (!event->attr.enable_on_exec)
                 return 0;
 
         event->attr.enable_on_exec = 0;
         if (event->state >= PERF_EVENT_STATE_INACTIVE)
                 return 0;
 
         __perf_event_mark_enabled(event);
 
         return 1;
 }
 
 /*
  * Enable all of a task's events that have been marked enable-on-exec.
  * This expects task == current.
  */
 static void perf_event_enable_on_exec(int ctxn)
 {
         struct perf_event_context *ctx, *clone_ctx = NULL;
         struct perf_cpu_context *cpuctx;
         struct perf_event *event;
         unsigned long flags;
         int enabled = 0;
 
         local_irq_save(flags);
         ctx = current->perf_event_ctxp[ctxn];
         if (!ctx || !ctx->nr_events)
                 goto out;
 
         cpuctx = __get_cpu_context(ctx);
         perf_ctx_lock(cpuctx, ctx);
         ctx_sched_out(ctx, cpuctx, EVENT_TIME);
         list_for_each_entry(event, &ctx->event_list, event_entry)
                 enabled |= event_enable_on_exec(event, ctx);
 
         /*
          * Unclone and reschedule this context if we enabled any event.
          */
         if (enabled) {
                 clone_ctx = unclone_ctx(ctx);
                 ctx_resched(cpuctx, ctx);
         }
         perf_ctx_unlock(cpuctx, ctx);
 
 out:
         local_irq_restore(flags);
 
         if (clone_ctx)
                 put_ctx(clone_ctx);
 }
 
 struct perf_read_data {
         struct perf_event *event;
         bool group;
         int ret;
 };
 
 /*
  * Cross CPU call to read the hardware event
  */
 static void __perf_event_read(void *info)
 {
         struct perf_read_data *data = info;
         struct perf_event *sub, *event = data->event;
         struct perf_event_context *ctx = event->ctx;
         struct perf_cpu_context *cpuctx = __get_cpu_context(ctx);
         struct pmu *pmu = event->pmu;
 
         /*
          * If this is a task context, we need to check whether it is
          * the current task context of this cpu.  If not it has been
          * scheduled out before the smp call arrived.  In that case
          * event->count would have been updated to a recent sample
          * when the event was scheduled out.
          */
         if (ctx->task && cpuctx->task_ctx != ctx)
                 return;
 
         raw_spin_lock(&ctx->lock);
         if (ctx->is_active) {
                 update_context_time(ctx);
                 update_cgrp_time_from_event(event);
         }
 
         update_event_times(event);
         if (event->state != PERF_EVENT_STATE_ACTIVE)
                 goto unlock;
 
         if (!data->group) {
                 pmu->read(event);
                 data->ret = 0;
                 goto unlock;
         }
 
         pmu->start_txn(pmu, PERF_PMU_TXN_READ);
 
         pmu->read(event);
 
         list_for_each_entry(sub, &event->sibling_list, group_entry) {
                 update_event_times(sub);
                 if (sub->state == PERF_EVENT_STATE_ACTIVE) {
                         /*
                          * Use sibling's PMU rather than @event's since
                          * sibling could be on different (eg: software) PMU.
                          */
                         sub->pmu->read(sub);
                 }
         }
 
         data->ret = pmu->commit_txn(pmu);
 
 unlock:
         raw_spin_unlock(&ctx->lock);
 }
 
 static inline u64 perf_event_count(struct perf_event *event)
 {
         if (event->pmu->count)
                 return event->pmu->count(event);
 
         return __perf_event_count(event);
 }
 
 /*
  * NMI-safe method to read a local event, that is an event that
  * is:
  *   - either for the current task, or for this CPU
  *   - does not have inherit set, for inherited task events
  *     will not be local and we cannot read them atomically
  *   - must not have a pmu::count method
  */
 u64 perf_event_read_local(struct perf_event *event)
 {
         unsigned long flags;
         u64 val;
 
         /*
          * Disabling interrupts avoids all counter scheduling (context
          * switches, timer based rotation and IPIs).
          */
         local_irq_save(flags);
 
         /* If this is a per-task event, it must be for current */
         WARN_ON_ONCE((event->attach_state & PERF_ATTACH_TASK) &&
                      event->hw.target != current);
 
         /* If this is a per-CPU event, it must be for this CPU */
         WARN_ON_ONCE(!(event->attach_state & PERF_ATTACH_TASK) &&
                      event->cpu != smp_processor_id());
 
         /*
          * It must not be an event with inherit set, we cannot read
          * all child counters from atomic context.
          */
         WARN_ON_ONCE(event->attr.inherit);
 
         /*
          * It must not have a pmu::count method, those are not
          * NMI safe.
          */
         WARN_ON_ONCE(event->pmu->count);
 
         /*
          * If the event is currently on this CPU, its either a per-task event,
          * or local to this CPU. Furthermore it means its ACTIVE (otherwise
          * oncpu == -1).
          */
         if (event->oncpu == smp_processor_id())
                 event->pmu->read(event);
 
         val = local64_read(&event->count);
         local_irq_restore(flags);
 
         return val;
 }
 
 static int perf_event_read(struct perf_event *event, bool group)
 {
         int ret = 0;
 
         /*
          * If event is enabled and currently active on a CPU, update the
          * value in the event structure:
          */
         if (event->state == PERF_EVENT_STATE_ACTIVE) {
                 struct perf_read_data data = {
                         .event = event,
                         .group = group,
                         .ret = 0,
                 };
                 smp_call_function_single(event->oncpu,
                                          __perf_event_read, &data, 1);
                 ret = data.ret;
         } else if (event->state == PERF_EVENT_STATE_INACTIVE) {
                 struct perf_event_context *ctx = event->ctx;
                 unsigned long flags;
 
                 raw_spin_lock_irqsave(&ctx->lock, flags);
                 /*
                  * may read while context is not active
                  * (e.g., thread is blocked), in that case
                  * we cannot update context time
                  */
                 if (ctx->is_active) {
                         update_context_time(ctx);
                         update_cgrp_time_from_event(event);
                 }
                 if (group)
                         update_group_times(event);
                 else
                         update_event_times(event);
                 raw_spin_unlock_irqrestore(&ctx->lock, flags);
         }
 
         return ret;
 }
 
 /*
  * Initialize the perf_event context in a task_struct:
  */
 static void __perf_event_init_context(struct perf_event_context *ctx)
 {
         raw_spin_lock_init(&ctx->lock);
         mutex_init(&ctx->mutex);
         INIT_LIST_HEAD(&ctx->active_ctx_list);
         INIT_LIST_HEAD(&ctx->pinned_groups);
         INIT_LIST_HEAD(&ctx->flexible_groups);
         INIT_LIST_HEAD(&ctx->event_list);
         atomic_set(&ctx->refcount, 1);
 }
 
 static struct perf_event_context *
 alloc_perf_context(struct pmu *pmu, struct task_struct *task)
 {
         struct perf_event_context *ctx;
 
         ctx = kzalloc(sizeof(struct perf_event_context), GFP_KERNEL);
         if (!ctx)
                 return NULL;
 
         __perf_event_init_context(ctx);
         if (task) {
                 ctx->task = task;
                 get_task_struct(task);
         }
         ctx->pmu = pmu;
 
         return ctx;
 }
 
 static struct task_struct *
 find_lively_task_by_vpid(pid_t vpid)
 {
         struct task_struct *task;
 
         rcu_read_lock();
         if (!vpid)
                 task = current;
         else
                 task = find_task_by_vpid(vpid);
         if (task)
                 get_task_struct(task);
         rcu_read_unlock();
 
         if (!task)
                 return ERR_PTR(-ESRCH);
 
         return task;
 }
 
 /*
  * Returns a matching context with refcount and pincount.
  */
 static struct perf_event_context *
 find_get_context(struct pmu *pmu, struct task_struct *task,
                 struct perf_event *event)
 {
         struct perf_event_context *ctx, *clone_ctx = NULL;
         struct perf_cpu_context *cpuctx;
         void *task_ctx_data = NULL;
         unsigned long flags;
         int ctxn, err;
         int cpu = event->cpu;
 
         if (!task) {
                 /* Must be root to operate on a CPU event: */
                 if (perf_paranoid_cpu() && !capable(CAP_SYS_ADMIN))
                         return ERR_PTR(-EACCES);
 
                 /*
                  * We could be clever and allow to attach a event to an
                  * offline CPU and activate it when the CPU comes up, but
                  * that's for later.
                  */
                 if (!cpu_online(cpu))
                         return ERR_PTR(-ENODEV);
 
                 cpuctx = per_cpu_ptr(pmu->pmu_cpu_context, cpu);
                 ctx = &cpuctx->ctx;
                 get_ctx(ctx);
                 ++ctx->pin_count;
 
                 return ctx;
         }
 
         err = -EINVAL;
         ctxn = pmu->task_ctx_nr;
         if (ctxn < 0)
                 goto errout;
 
         if (event->attach_state & PERF_ATTACH_TASK_DATA) {
                 task_ctx_data = kzalloc(pmu->task_ctx_size, GFP_KERNEL);
                 if (!task_ctx_data) {
                         err = -ENOMEM;
                         goto errout;
                 }
         }
 
 retry:
         ctx = perf_lock_task_context(task, ctxn, &flags);
         if (ctx) {
                 clone_ctx = unclone_ctx(ctx);
                 ++ctx->pin_count;
 
                 if (task_ctx_data && !ctx->task_ctx_data) {
                         ctx->task_ctx_data = task_ctx_data;
                         task_ctx_data = NULL;
                 }
                 raw_spin_unlock_irqrestore(&ctx->lock, flags);
 
                 if (clone_ctx)
                         put_ctx(clone_ctx);
         } else {
                 ctx = alloc_perf_context(pmu, task);
                 err = -ENOMEM;
                 if (!ctx)
                         goto errout;
 
                 if (task_ctx_data) {
                         ctx->task_ctx_data = task_ctx_data;
                         task_ctx_data = NULL;
                 }
 
                 err = 0;
                 mutex_lock(&task->perf_event_mutex);
                 /*
                  * If it has already passed perf_event_exit_task().
                  * we must see PF_EXITING, it takes this mutex too.
                  */
                 if (task->flags & PF_EXITING)
                         err = -ESRCH;
                 else if (task->perf_event_ctxp[ctxn])
                         err = -EAGAIN;
                 else {
                         get_ctx(ctx);
                         ++ctx->pin_count;
                         rcu_assign_pointer(task->perf_event_ctxp[ctxn], ctx);
                 }
                 mutex_unlock(&task->perf_event_mutex);
 
                 if (unlikely(err)) {
                         put_ctx(ctx);
 
                         if (err == -EAGAIN)
                                 goto retry;
                         goto errout;
                 }
         }
 
         kfree(task_ctx_data);
         return ctx;
 
 errout:
         kfree(task_ctx_data);
         return ERR_PTR(err);
 }
 
 static void perf_event_free_filter(struct perf_event *event);
 static void perf_event_free_bpf_prog(struct perf_event *event);
 
 static void free_event_rcu(struct rcu_head *head)
 {
         struct perf_event *event;
 
         event = container_of(head, struct perf_event, rcu_head);
         if (event->ns)
                 put_pid_ns(event->ns);
         perf_event_free_filter(event);
         kfree(event);
 }
 
 static void ring_buffer_attach(struct perf_event *event,
                                struct ring_buffer *rb);
 
 static void unaccount_event_cpu(struct perf_event *event, int cpu)
 {
         if (event->parent)
                 return;
 
         if (is_cgroup_event(event))
                 atomic_dec(&per_cpu(perf_cgroup_events, cpu));
 }
 
 #ifdef CONFIG_NO_HZ_FULL
 static DEFINE_SPINLOCK(nr_freq_lock);
 #endif
 
 static void unaccount_freq_event_nohz(void)
 {
 #ifdef CONFIG_NO_HZ_FULL
         spin_lock(&nr_freq_lock);
         if (atomic_dec_and_test(&nr_freq_events))
                 tick_nohz_dep_clear(TICK_DEP_BIT_PERF_EVENTS);
         spin_unlock(&nr_freq_lock);
 #endif
 }
 
 static void unaccount_freq_event(void)
 {
         if (tick_nohz_full_enabled())
                 unaccount_freq_event_nohz();
         else
                 atomic_dec(&nr_freq_events);
 }
 
 static void unaccount_event(struct perf_event *event)
 {
         bool dec = false;
 
         if (event->parent)
                 return;
 
         if (event->attach_state & PERF_ATTACH_TASK)
                 dec = true;
         if (event->attr.mmap || event->attr.mmap_data)
                 atomic_dec(&nr_mmap_events);
         if (event->attr.comm)
                 atomic_dec(&nr_comm_events);
         if (event->attr.task)
                 atomic_dec(&nr_task_events);
         if (event->attr.freq)
                 unaccount_freq_event();
         if (event->attr.context_switch) {
                 dec = true;
                 atomic_dec(&nr_switch_events);
         }
         if (is_cgroup_event(event))
                 dec = true;
         if (has_branch_stack(event))
                 dec = true;
 
         if (dec) {
                 if (!atomic_add_unless(&perf_sched_count, -1, 1))
                         schedule_delayed_work(&perf_sched_work, HZ);
         }
 
         unaccount_event_cpu(event, event->cpu);
 }
 
 static void perf_sched_delayed(struct work_struct *work)
 {
         mutex_lock(&perf_sched_mutex);
         if (atomic_dec_and_test(&perf_sched_count))
                 static_branch_disable(&perf_sched_events);
         mutex_unlock(&perf_sched_mutex);
 }
 
 /*
  * The following implement mutual exclusion of events on "exclusive" pmus
  * (PERF_PMU_CAP_EXCLUSIVE). Such pmus can only have one event scheduled
  * at a time, so we disallow creating events that might conflict, namely:
  *
  *  1) cpu-wide events in the presence of per-task events,
  *  2) per-task events in the presence of cpu-wide events,
  *  3) two matching events on the same context.
  *
  * The former two cases are handled in the allocation path (perf_event_alloc(),
  * _free_event()), the latter -- before the first perf_install_in_context().
  */
 static int exclusive_event_init(struct perf_event *event)
 {
         struct pmu *pmu = event->pmu;
 
         if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
                 return 0;
 
         /*
          * Prevent co-existence of per-task and cpu-wide events on the
          * same exclusive pmu.
          *
          * Negative pmu::exclusive_cnt means there are cpu-wide
          * events on this "exclusive" pmu, positive means there are
          * per-task events.
          *
          * Since this is called in perf_event_alloc() path, event::ctx
          * doesn't exist yet; it is, however, safe to use PERF_ATTACH_TASK
          * to mean "per-task event", because unlike other attach states it
          * never gets cleared.
          */
         if (event->attach_state & PERF_ATTACH_TASK) {
                 if (!atomic_inc_unless_negative(&pmu->exclusive_cnt))
                         return -EBUSY;
         } else {
                 if (!atomic_dec_unless_positive(&pmu->exclusive_cnt))
                         return -EBUSY;
         }
 
         return 0;
 }
 
 static void exclusive_event_destroy(struct perf_event *event)
 {
         struct pmu *pmu = event->pmu;
 
         if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
                 return;
 
         /* see comment in exclusive_event_init() */
         if (event->attach_state & PERF_ATTACH_TASK)
                 atomic_dec(&pmu->exclusive_cnt);
         else
                 atomic_inc(&pmu->exclusive_cnt);
 }
 
 static bool exclusive_event_match(struct perf_event *e1, struct perf_event *e2)
 {
         if ((e1->pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE) &&
             (e1->cpu == e2->cpu ||
              e1->cpu == -1 ||
              e2->cpu == -1))
                 return true;
         return false;
 }
 
 /* Called under the same ctx::mutex as perf_install_in_context() */
 static bool exclusive_event_installable(struct perf_event *event,
                                         struct perf_event_context *ctx)
 {
         struct perf_event *iter_event;
         struct pmu *pmu = event->pmu;
 
         if (!(pmu->capabilities & PERF_PMU_CAP_EXCLUSIVE))
                 return true;
 
         list_for_each_entry(iter_event, &ctx->event_list, event_entry) {
                 if (exclusive_event_match(iter_event, event))
                         return false;
         }
 
         return true;
 }
 
 static void perf_addr_filters_splice(struct perf_event *event,
                                        struct list_head *head);
 
 static void _free_event(struct perf_event *event)
 {
         irq_work_sync(&event->pending);
 
         unaccount_event(event);
 
         if (event->rb) {
                 /*
                  * Can happen when we close an event with re-directed output.
                  *
                  * Since we have a 0 refcount, perf_mmap_close() will skip
                  * over us; possibly making our ring_buffer_put() the last.
                  */
                 mutex_lock(&event->mmap_mutex);
                 ring_buffer_attach(event, NULL);
                 mutex_unlock(&event->mmap_mutex);
         }
 
         if (is_cgroup_event(event))
                 perf_detach_cgroup(event);
 
         if (!event->parent) {
                 if (event->attr.sample_type & PERF_SAMPLE_CALLCHAIN)
                         put_callchain_buffers();
         }
 
         perf_event_free_bpf_prog(event);
         perf_addr_filters_splice(event, NULL);
         kfree(event->addr_filters_offs);
 
         if (event->destroy)
                 event->destroy(event);
 
         if (event->ctx)
                 put_ctx(event->ctx);
 
         exclusive_event_destroy(event);
         module_put(event->pmu->module);
 
         call_rcu(&event->rcu_head, free_event_rcu);
 }
 
 /*
  * Used to free events which have a known refcount of 1, such as in error paths
  * where the event isn't exposed yet and inherited events.
  */
 static void free_event(struct perf_event *event)
 {
         if (WARN(atomic_long_cmpxchg(&event->refcount, 1, 0) != 1,
                                 "unexpected event refcount: %ld; ptr=%p\n",
                                 atomic_long_read(&event->refcount), event)) {
                 /* leak to avoid use-after-free */
                 return;
         }
 
         _free_event(event);
 }
 
 /*
  * Remove user event from the owner task.
  */
 static void perf_remove_from_owner(struct perf_event *event)
 {
         struct task_struct *owner;
 
         rcu_read_lock();
         /*
          * Matches the smp_store_release() in perf_event_exit_task(). If we
          * observe !owner it means the list deletion is complete and we can
          * indeed free this event, otherwise we need to serialize on
          * owner->perf_event_mutex.
          */
         owner = lockless_dereference(event->owner);
         if (owner) {
                 /*
                  * Since delayed_put_task_struct() also drops the last
                  * task reference we can safely take a new reference
                  * while holding the rcu_read_lock().
                  */
                 get_task_struct(owner);
         }
         rcu_read_unlock();
 
         if (owner) {
                 /*
                  * If we're here through perf_event_exit_task() we're already
                  * holding ctx->mutex which would be an inversion wrt. the
                  * normal lock order.
                  *
                  * However we can safely take this lock because its the child
                  * ctx->mutex.
                  */
                 mutex_lock_nested(&owner->perf_event_mutex, SINGLE_DEPTH_NESTING);
 
                 /*
                  * We have to re-check the event->owner field, if it is cleared
                  * we raced with perf_event_exit_task(), acquiring the mutex
                  * ensured they're done, and we can proceed with freeing the
                  * event.
                  */
                 if (event->owner) {
                         list_del_init(&event->owner_entry);
                         smp_store_release(&event->owner, NULL);
                 }
                 mutex_unlock(&owner->perf_event_mutex);
                 put_task_struct(owner);
         }
 }
 
 static void put_event(struct perf_event *event)
 {
         if (!atomic_long_dec_and_test(&event->refcount))
                 return;
 
         _free_event(event);
 }
 
 /*
  * Kill an event dead; while event:refcount will preserve the event
  * object, it will not preserve its functionality. Once the last 'user'
  * gives up the object, we'll destroy the thing.
  */
 int perf_event_release_kernel(struct perf_event *event)
 {
         struct perf_event_context *ctx = event->ctx;
         struct perf_event *child, *tmp;
 
         /*
          * If we got here through err_file: fput(event_file); we will not have
          * attached to a context yet.
          */
         if (!ctx) {
                 WARN_ON_ONCE(event->attach_state &
                                 (PERF_ATTACH_CONTEXT|PERF_ATTACH_GROUP));
                 goto no_ctx;
         }
 
         if (!is_kernel_event(event))
                 perf_remove_from_owner(event);
 
         ctx = perf_event_ctx_lock(event);
         WARN_ON_ONCE(ctx->parent_ctx);
         perf_remove_from_context(event, DETACH_GROUP);
 
         raw_spin_lock_irq(&ctx->lock);
         /*
          * Mark this even as STATE_DEAD, there is no external reference to it
          * anymore.
          *
          * Anybody acquiring event->child_mutex after the below loop _must_
          * also see this, most importantly inherit_event() which will avoid
          * placing more children on the list.
          *
          * Thus this guarantees that we will in fact observe and kill _ALL_
          * child events.
          */
         event->state = PERF_EVENT_STATE_DEAD;
         raw_spin_unlock_irq(&ctx->lock);
 
         perf_event_ctx_unlock(event, ctx);
 
 again:
         mutex_lock(&event->child_mutex);
         list_for_each_entry(child, &event->child_list, child_list) {
 
                 /*
                  * Cannot change, child events are not migrated, see the
                  * comment with perf_event_ctx_lock_nested().
                  */
                 ctx = lockless_dereference(child->ctx);
                 /*
                  * Since child_mutex nests inside ctx::mutex, we must jump
                  * through hoops. We start by grabbing a reference on the ctx.
                  *
                  * Since the event cannot get freed while we hold the
                  * child_mutex, the context must also exist and have a !0
                  * reference count.
                  */
                 get_ctx(ctx);
 
                 /*
                  * Now that we have a ctx ref, we can drop child_mutex, and
                  * acquire ctx::mutex without fear of it going away. Then we
                  * can re-acquire child_mutex.
                  */
                 mutex_unlock(&event->child_mutex);
                 mutex_lock(&ctx->mutex);
                 mutex_lock(&event->child_mutex);
 
                 /*
                  * Now that we hold ctx::mutex and child_mutex, revalidate our
                  * state, if child is still the first entry, it didn't get freed
                  * and we can continue doing so.
                  */
                 tmp = list_first_entry_or_null(&event->child_list,
                                                struct perf_event, child_list);
                 if (tmp == child) {
                         perf_remove_from_context(child, DETACH_GROUP);
                         list_del(&child->child_list);
                         free_event(child);
                         /*
                          * This matches the refcount bump in inherit_event();
                          * this can't be the last reference.
                          */
                         put_event(event);
                 }
 
                 mutex_unlock(&event->child_mutex);
                 mutex_unlock(&ctx->mutex);
                 put_ctx(ctx);
                 goto again;
         }
         mutex_unlock(&event->child_mutex);
 
 no_ctx:
         put_event(event); /* Must be the 'last' reference */
         return 0;
 }
 EXPORT_SYMBOL_GPL(perf_event_release_kernel);
 
 /*
  * Called when the last reference to the file is gone.
  */
 static int perf_release(struct inode *inode, struct file *file)
 {
         perf_event_release_kernel(file->private_data);
         return 0;
 }
 
 u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running)
 {
         struct perf_event *child;
         u64 total = 0;
 
         *enabled = 0;
         *running = 0;
 
         mutex_lock(&event->child_mutex);
 
         (void)perf_event_read(event, false);
         total += perf_event_count(event);
 
         *enabled += event->total_time_enabled +
                         atomic64_read(&event->child_total_time_enabled);
         *running += event->total_time_running +
                         atomic64_read(&event->child_total_time_running);
 
         list_for_each_entry(child, &event->child_list, child_list) {
                 (void)perf_event_read(child, false);
                 total += perf_event_count(child);
                 *enabled += child->total_time_enabled;
                 *running += child->total_time_running;
         }
         mutex_unlock(&event->child_mutex);
 
         return total;
 }
 EXPORT_SYMBOL_GPL(perf_event_read_value);
 
 static int __perf_read_group_add(struct perf_event *leader,
                                         u64 read_format, u64 *values)
 {
         struct perf_event *sub;
         int n = 1; /* skip @nr */
         int ret;
 
         ret = perf_event_read(leader, true);
         if (ret)
                 return ret;
 
         /*
          * Since we co-schedule groups, {enabled,running} times of siblings
          * will be identical to those of the leader, so we only publish one
          * set.
          */
         if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
                 values[n++] += leader->total_time_enabled +
                         atomic64_read(&leader->child_total_time_enabled);
         }
 
         if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
                 values[n++] += leader->total_time_running +
                         atomic64_read(&leader->child_total_time_running);
         }
 
         /*
          * Write {count,id} tuples for every sibling.
          */
         values[n++] += perf_event_count(leader);
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(leader);
 
         list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                 values[n++] += perf_event_count(sub);
                 if (read_format & PERF_FORMAT_ID)
                         values[n++] = primary_event_id(sub);
         }
 
         return 0;
 }
 
 static int perf_read_group(struct perf_event *event,
                                    u64 read_format, char __user *buf)
 {
         struct perf_event *leader = event->group_leader, *child;
         struct perf_event_context *ctx = leader->ctx;
         int ret;
         u64 *values;
 
         lockdep_assert_held(&ctx->mutex);
 
         values = kzalloc(event->read_size, GFP_KERNEL);
         if (!values)
                 return -ENOMEM;
 
         values[0] = 1 + leader->nr_siblings;
 
         /*
          * By locking the child_mutex of the leader we effectively
          * lock the child list of all siblings.. XXX explain how.
          */
         mutex_lock(&leader->child_mutex);
 
         ret = __perf_read_group_add(leader, read_format, values);
         if (ret)
                 goto unlock;
 
         list_for_each_entry(child, &leader->child_list, child_list) {
                 ret = __perf_read_group_add(child, read_format, values);
                 if (ret)
                         goto unlock;
         }
 
         mutex_unlock(&leader->child_mutex);
 
         ret = event->read_size;
         if (copy_to_user(buf, values, event->read_size))
                 ret = -EFAULT;
         goto out;
 
 unlock:
         mutex_unlock(&leader->child_mutex);
 out:
         kfree(values);
         return ret;
 }
 
 static int perf_read_one(struct perf_event *event,
                                  u64 read_format, char __user *buf)
 {
         u64 enabled, running;
         u64 values[4];
         int n = 0;
 
         values[n++] = perf_event_read_value(event, &enabled, &running);
         if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                 values[n++] = enabled;
         if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                 values[n++] = running;
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(event);
 
         if (copy_to_user(buf, values, n * sizeof(u64)))
                 return -EFAULT;
 
         return n * sizeof(u64);
 }
 
 static bool is_event_hup(struct perf_event *event)
 {
         bool no_children;
 
         if (event->state > PERF_EVENT_STATE_EXIT)
                 return false;
 
         mutex_lock(&event->child_mutex);
         no_children = list_empty(&event->child_list);
         mutex_unlock(&event->child_mutex);
         return no_children;
 }
 
 /*
  * Read the performance event - simple non blocking version for now
  */
 static ssize_t
 __perf_read(struct perf_event *event, char __user *buf, size_t count)
 {
         u64 read_format = event->attr.read_format;
         int ret;
 
         /*
          * Return end-of-file for a read on a event that is in
          * error state (i.e. because it was pinned but it couldn't be
          * scheduled on to the CPU at some point).
          */
         if (event->state == PERF_EVENT_STATE_ERROR)
                 return 0;
 
         if (count < event->read_size)
                 return -ENOSPC;
 
         WARN_ON_ONCE(event->ctx->parent_ctx);
         if (read_format & PERF_FORMAT_GROUP)
                 ret = perf_read_group(event, read_format, buf);
         else
                 ret = perf_read_one(event, read_format, buf);
 
         return ret;
 }
 
 static ssize_t
 perf_read(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 {
         struct perf_event *event = file->private_data;
         struct perf_event_context *ctx;
         int ret;
 
         ctx = perf_event_ctx_lock(event);
         ret = __perf_read(event, buf, count);
         perf_event_ctx_unlock(event, ctx);
 
         return ret;
 }
 
 static unsigned int perf_poll(struct file *file, poll_table *wait)
 {
         struct perf_event *event = file->private_data;
         struct ring_buffer *rb;
         unsigned int events = POLLHUP;
 
         poll_wait(file, &event->waitq, wait);
 
         if (is_event_hup(event))
                 return events;
 
         /*
          * Pin the event->rb by taking event->mmap_mutex; otherwise
          * perf_event_set_output() can swizzle our rb and make us miss wakeups.
          */
         mutex_lock(&event->mmap_mutex);
         rb = event->rb;
         if (rb)
                 events = atomic_xchg(&rb->poll, 0);
         mutex_unlock(&event->mmap_mutex);
         return events;
 }
 
 static void _perf_event_reset(struct perf_event *event)
 {
         (void)perf_event_read(event, false);
         local64_set(&event->count, 0);
         perf_event_update_userpage(event);
 }
 
 /*
  * Holding the top-level event's child_mutex means that any
  * descendant process that has inherited this event will block
  * in perf_event_exit_event() if it goes to exit, thus satisfying the
  * task existence requirements of perf_event_enable/disable.
  */
 static void perf_event_for_each_child(struct perf_event *event,
                                         void (*func)(struct perf_event *))
 {
         struct perf_event *child;
 
         WARN_ON_ONCE(event->ctx->parent_ctx);
 
         mutex_lock(&event->child_mutex);
         func(event);
         list_for_each_entry(child, &event->child_list, child_list)
                 func(child);
         mutex_unlock(&event->child_mutex);
 }
 
 static void perf_event_for_each(struct perf_event *event,
                                   void (*func)(struct perf_event *))
 {
         struct perf_event_context *ctx = event->ctx;
         struct perf_event *sibling;
 
         lockdep_assert_held(&ctx->mutex);
 
         event = event->group_leader;
 
         perf_event_for_each_child(event, func);
         list_for_each_entry(sibling, &event->sibling_list, group_entry)
                 perf_event_for_each_child(sibling, func);
 }
 
 static void __perf_event_period(struct perf_event *event,
                                 struct perf_cpu_context *cpuctx,
                                 struct perf_event_context *ctx,
                                 void *info)
 {
         u64 value = *((u64 *)info);
         bool active;
 
         if (event->attr.freq) {
                 event->attr.sample_freq = value;
         } else {
                 event->attr.sample_period = value;
                 event->hw.sample_period = value;
         }
 
         active = (event->state == PERF_EVENT_STATE_ACTIVE);
         if (active) {
                 perf_pmu_disable(ctx->pmu);
                 /*
                  * We could be throttled; unthrottle now to avoid the tick
                  * trying to unthrottle while we already re-started the event.
                  */
                 if (event->hw.interrupts == MAX_INTERRUPTS) {
                         event->hw.interrupts = 0;
                         perf_log_throttle(event, 1);
                 }
                 event->pmu->stop(event, PERF_EF_UPDATE);
         }
 
         local64_set(&event->hw.period_left, 0);
 
         if (active) {
                 event->pmu->start(event, PERF_EF_RELOAD);
                 perf_pmu_enable(ctx->pmu);
         }
 }
 
 static int perf_event_period(struct perf_event *event, u64 __user *arg)
 {
         u64 value;
 
         if (!is_sampling_event(event))
                 return -EINVAL;
 
         if (copy_from_user(&value, arg, sizeof(value)))
                 return -EFAULT;
 
         if (!value)
                 return -EINVAL;
 
         if (event->attr.freq && value > sysctl_perf_event_sample_rate)
                 return -EINVAL;
 
         event_function_call(event, __perf_event_period, &value);
 
         return 0;
 }
 
 static const struct file_operations perf_fops;
 
 static inline int perf_fget_light(int fd, struct fd *p)
 {
         struct fd f = fdget(fd);
         if (!f.file)
                 return -EBADF;
 
         if (f.file->f_op != &perf_fops) {
                 fdput(f);
                 return -EBADF;
         }
         *p = f;
         return 0;
 }
 
 static int perf_event_set_output(struct perf_event *event,
                                  struct perf_event *output_event);
 static int perf_event_set_filter(struct perf_event *event, void __user *arg);
 static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd);
 
 static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned long arg)
 {
         void (*func)(struct perf_event *);
         u32 flags = arg;
 
         switch (cmd) {
         case PERF_EVENT_IOC_ENABLE:
                 func = _perf_event_enable;
                 break;
         case PERF_EVENT_IOC_DISABLE:
                 func = _perf_event_disable;
                 break;
         case PERF_EVENT_IOC_RESET:
                 func = _perf_event_reset;
                 break;
 
         case PERF_EVENT_IOC_REFRESH:
                 return _perf_event_refresh(event, arg);
 
         case PERF_EVENT_IOC_PERIOD:
                 return perf_event_period(event, (u64 __user *)arg);
 
         case PERF_EVENT_IOC_ID:
         {
                 u64 id = primary_event_id(event);
 
                 if (copy_to_user((void __user *)arg, &id, sizeof(id)))
                         return -EFAULT;
                 return 0;
         }
 
         case PERF_EVENT_IOC_SET_OUTPUT:
         {
                 int ret;
                 if (arg != -1) {
                         struct perf_event *output_event;
                         struct fd output;
                         ret = perf_fget_light(arg, &output);
                         if (ret)
                                 return ret;
                         output_event = output.file->private_data;
                         ret = perf_event_set_output(event, output_event);
                         fdput(output);
                 } else {
                         ret = perf_event_set_output(event, NULL);
                 }
                 return ret;
         }
 
         case PERF_EVENT_IOC_SET_FILTER:
                 return perf_event_set_filter(event, (void __user *)arg);
 
         case PERF_EVENT_IOC_SET_BPF:
                 return perf_event_set_bpf_prog(event, arg);
 
         case PERF_EVENT_IOC_PAUSE_OUTPUT: {
                 struct ring_buffer *rb;
 
                 rcu_read_lock();
                 rb = rcu_dereference(event->rb);
                 if (!rb || !rb->nr_pages) {
                         rcu_read_unlock();
                         return -EINVAL;
                 }
                 rb_toggle_paused(rb, !!arg);
                 rcu_read_unlock();
                 return 0;
         }
         default:
                 return -ENOTTY;
         }
 
         if (flags & PERF_IOC_FLAG_GROUP)
                 perf_event_for_each(event, func);
         else
                 perf_event_for_each_child(event, func);
 
         return 0;
 }
 
 static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 {
         struct perf_event *event = file->private_data;
         struct perf_event_context *ctx;
         long ret;
 
         ctx = perf_event_ctx_lock(event);
         ret = _perf_ioctl(event, cmd, arg);
         perf_event_ctx_unlock(event, ctx);
 
         return ret;
 }
 
 #ifdef CONFIG_COMPAT
 static long perf_compat_ioctl(struct file *file, unsigned int cmd,
                                 unsigned long arg)
 {
         switch (_IOC_NR(cmd)) {
         case _IOC_NR(PERF_EVENT_IOC_SET_FILTER):
         case _IOC_NR(PERF_EVENT_IOC_ID):
                 /* Fix up pointer size (usually 4 -> 8 in 32-on-64-bit case */
                 if (_IOC_SIZE(cmd) == sizeof(compat_uptr_t)) {
                         cmd &= ~IOCSIZE_MASK;
                         cmd |= sizeof(void *) << IOCSIZE_SHIFT;
                 }
                 break;
         }
         return perf_ioctl(file, cmd, arg);
 }
 #else
 # define perf_compat_ioctl NULL
 #endif
 
 int perf_event_task_enable(void)
 {
         struct perf_event_context *ctx;
         struct perf_event *event;
 
         mutex_lock(&current->perf_event_mutex);
         list_for_each_entry(event, &current->perf_event_list, owner_entry) {
                 ctx = perf_event_ctx_lock(event);
                 perf_event_for_each_child(event, _perf_event_enable);
                 perf_event_ctx_unlock(event, ctx);
         }
         mutex_unlock(&current->perf_event_mutex);
 
         return 0;
 }
 
 int perf_event_task_disable(void)
 {
         struct perf_event_context *ctx;
         struct perf_event *event;
 
         mutex_lock(&current->perf_event_mutex);
         list_for_each_entry(event, &current->perf_event_list, owner_entry) {
                 ctx = perf_event_ctx_lock(event);
                 perf_event_for_each_child(event, _perf_event_disable);
                 perf_event_ctx_unlock(event, ctx);
         }
         mutex_unlock(&current->perf_event_mutex);
 
         return 0;
 }
 
 static int perf_event_index(struct perf_event *event)
 {
         if (event->hw.state & PERF_HES_STOPPED)
                 return 0;
 
         if (event->state != PERF_EVENT_STATE_ACTIVE)
                 return 0;
 
         return event->pmu->event_idx(event);
 }
 
 static void calc_timer_values(struct perf_event *event,
                                 u64 *now,
                                 u64 *enabled,
                                 u64 *running)
 {
         u64 ctx_time;
 
         *now = perf_clock();
         ctx_time = event->shadow_ctx_time + *now;
         *enabled = ctx_time - event->tstamp_enabled;
         *running = ctx_time - event->tstamp_running;
 }
 
 static void perf_event_init_userpage(struct perf_event *event)
 {
         struct perf_event_mmap_page *userpg;
         struct ring_buffer *rb;
 
         rcu_read_lock();
         rb = rcu_dereference(event->rb);
         if (!rb)
                 goto unlock;
 
         userpg = rb->user_page;
 
         /* Allow new userspace to detect that bit 0 is deprecated */
         userpg->cap_bit0_is_deprecated = 1;
         userpg->size = offsetof(struct perf_event_mmap_page, __reserved);
         userpg->data_offset = PAGE_SIZE;
         userpg->data_size = perf_data_size(rb);
 
 unlock:
         rcu_read_unlock();
 }
 
 void __weak arch_perf_update_userpage(
         struct perf_event *event, struct perf_event_mmap_page *userpg, u64 now)
 {
 }
 
 /*
  * Callers need to ensure there can be no nesting of this function, otherwise
  * the seqlock logic goes bad. We can not serialize this because the arch
  * code calls this from NMI context.
  */
 void perf_event_update_userpage(struct perf_event *event)
 {
         struct perf_event_mmap_page *userpg;
         struct ring_buffer *rb;
         u64 enabled, running, now;
 
         rcu_read_lock();
         rb = rcu_dereference(event->rb);
         if (!rb)
                 goto unlock;
 
         /*
          * compute total_time_enabled, total_time_running
          * based on snapshot values taken when the event
          * was last scheduled in.
          *
          * we cannot simply called update_context_time()
          * because of locking issue as we can be called in
          * NMI context
          */
         calc_timer_values(event, &now, &enabled, &running);
 
         userpg = rb->user_page;
         /*
          * Disable preemption so as to not let the corresponding user-space
          * spin too long if we get preempted.
          */
         preempt_disable();
         ++userpg->lock;
         barrier();
         userpg->index = perf_event_index(event);
         userpg->offset = perf_event_count(event);
         if (userpg->index)
                 userpg->offset -= local64_read(&event->hw.prev_count);
 
         userpg->time_enabled = enabled +
                         atomic64_read(&event->child_total_time_enabled);
 
         userpg->time_running = running +
                         atomic64_read(&event->child_total_time_running);
 
         arch_perf_update_userpage(event, userpg, now);
 
         barrier();
         ++userpg->lock;
         preempt_enable();
 unlock:
         rcu_read_unlock();
 }
 
 static int perf_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
         struct perf_event *event = vma->vm_file->private_data;
         struct ring_buffer *rb;
         int ret = VM_FAULT_SIGBUS;
 
         if (vmf->flags & FAULT_FLAG_MKWRITE) {
                 if (vmf->pgoff == 0)
                         ret = 0;
                 return ret;
         }
 
         rcu_read_lock();
         rb = rcu_dereference(event->rb);
         if (!rb)
                 goto unlock;
 
         if (vmf->pgoff && (vmf->flags & FAULT_FLAG_WRITE))
                 goto unlock;
 
         vmf->page = perf_mmap_to_page(rb, vmf->pgoff);
         if (!vmf->page)
                 goto unlock;
 
         get_page(vmf->page);
         vmf->page->mapping = vma->vm_file->f_mapping;
         vmf->page->index   = vmf->pgoff;
 
         ret = 0;
 unlock:
         rcu_read_unlock();
 
         return ret;
 }
 
 static void ring_buffer_attach(struct perf_event *event,
                                struct ring_buffer *rb)
 {
         struct ring_buffer *old_rb = NULL;
         unsigned long flags;
 
         if (event->rb) {
                 /*
                  * Should be impossible, we set this when removing
                  * event->rb_entry and wait/clear when adding event->rb_entry.
                  */
                 WARN_ON_ONCE(event->rcu_pending);
 
                 old_rb = event->rb;
                 spin_lock_irqsave(&old_rb->event_lock, flags);
                 list_del_rcu(&event->rb_entry);
                 spin_unlock_irqrestore(&old_rb->event_lock, flags);
 
                 event->rcu_batches = get_state_synchronize_rcu();
                 event->rcu_pending = 1;
         }
 
         if (rb) {
                 if (event->rcu_pending) {
                         cond_synchronize_rcu(event->rcu_batches);
                         event->rcu_pending = 0;
                 }
 
                 spin_lock_irqsave(&rb->event_lock, flags);
                 list_add_rcu(&event->rb_entry, &rb->event_list);
                 spin_unlock_irqrestore(&rb->event_lock, flags);
         }
 
         rcu_assign_pointer(event->rb, rb);
 
         if (old_rb) {
                 ring_buffer_put(old_rb);
                 /*
                  * Since we detached before setting the new rb, so that we
                  * could attach the new rb, we could have missed a wakeup.
                  * Provide it now.
                  */
                 wake_up_all(&event->waitq);
         }
 }
 
 static void ring_buffer_wakeup(struct perf_event *event)
 {
         struct ring_buffer *rb;
 
         rcu_read_lock();
         rb = rcu_dereference(event->rb);
         if (rb) {
                 list_for_each_entry_rcu(event, &rb->event_list, rb_entry)
                         wake_up_all(&event->waitq);
         }
         rcu_read_unlock();
 }
 
 struct ring_buffer *ring_buffer_get(struct perf_event *event)
 {
         struct ring_buffer *rb;
 
         rcu_read_lock();
         rb = rcu_dereference(event->rb);
         if (rb) {
                 if (!atomic_inc_not_zero(&rb->refcount))
                         rb = NULL;
         }
         rcu_read_unlock();
 
         return rb;
 }
 
 void ring_buffer_put(struct ring_buffer *rb)
 {
         if (!atomic_dec_and_test(&rb->refcount))
                 return;
 
         WARN_ON_ONCE(!list_empty(&rb->event_list));
 
         call_rcu(&rb->rcu_head, rb_free_rcu);
 }
 
 static void perf_mmap_open(struct vm_area_struct *vma)
 {
         struct perf_event *event = vma->vm_file->private_data;
 
         atomic_inc(&event->mmap_count);
         atomic_inc(&event->rb->mmap_count);
 
         if (vma->vm_pgoff)
                 atomic_inc(&event->rb->aux_mmap_count);
 
         if (event->pmu->event_mapped)
                 event->pmu->event_mapped(event);
 }
 
 static void perf_pmu_output_stop(struct perf_event *event);
 
 /*
  * A buffer can be mmap()ed multiple times; either directly through the same
  * event, or through other events by use of perf_event_set_output().
  *
  * In order to undo the VM accounting done by perf_mmap() we need to destroy
  * the buffer here, where we still have a VM context. This means we need
  * to detach all events redirecting to us.
  */
 static void perf_mmap_close(struct vm_area_struct *vma)
 {
         struct perf_event *event = vma->vm_file->private_data;
 
         struct ring_buffer *rb = ring_buffer_get(event);
         struct user_struct *mmap_user = rb->mmap_user;
         int mmap_locked = rb->mmap_locked;
         unsigned long size = perf_data_size(rb);
 
         if (event->pmu->event_unmapped)
                 event->pmu->event_unmapped(event);
 
         /*
          * rb->aux_mmap_count will always drop before rb->mmap_count and
          * event->mmap_count, so it is ok to use event->mmap_mutex to
          * serialize with perf_mmap here.
          */
         if (rb_has_aux(rb) && vma->vm_pgoff == rb->aux_pgoff &&
             atomic_dec_and_mutex_lock(&rb->aux_mmap_count, &event->mmap_mutex)) {
                 /*
                  * Stop all AUX events that are writing to this buffer,
                  * so that we can free its AUX pages and corresponding PMU
                  * data. Note that after rb::aux_mmap_count dropped to zero,
                  * they won't start any more (see perf_aux_output_begin()).
                  */
                 perf_pmu_output_stop(event);
 
                 /* now it's safe to free the pages */
                 atomic_long_sub(rb->aux_nr_pages, &mmap_user->locked_vm);
                 vma->vm_mm->pinned_vm -= rb->aux_mmap_locked;
 
                 /* this has to be the last one */
                 rb_free_aux(rb);
                 WARN_ON_ONCE(atomic_read(&rb->aux_refcount));
 
                 mutex_unlock(&event->mmap_mutex);
         }
 
         atomic_dec(&rb->mmap_count);
 
         if (!atomic_dec_and_mutex_lock(&event->mmap_count, &event->mmap_mutex))
                 goto out_put;
 
         ring_buffer_attach(event, NULL);
         mutex_unlock(&event->mmap_mutex);
 
         /* If there's still other mmap()s of this buffer, we're done. */
         if (atomic_read(&rb->mmap_count))
                 goto out_put;
 
         /*
          * No other mmap()s, detach from all other events that might redirect
          * into the now unreachable buffer. Somewhat complicated by the
          * fact that rb::event_lock otherwise nests inside mmap_mutex.
          */
 again:
         rcu_read_lock();
         list_for_each_entry_rcu(event, &rb->event_list, rb_entry) {
                 if (!atomic_long_inc_not_zero(&event->refcount)) {
                         /*
                          * This event is en-route to free_event() which will
                          * detach it and remove it from the list.
                          */
                         continue;
                 }
                 rcu_read_unlock();
 
                 mutex_lock(&event->mmap_mutex);
                 /*
                  * Check we didn't race with perf_event_set_output() which can
                  * swizzle the rb from under us while we were waiting to
                  * acquire mmap_mutex.
                  *
                  * If we find a different rb; ignore this event, a next
                  * iteration will no longer find it on the list. We have to
                  * still restart the iteration to make sure we're not now
                  * iterating the wrong list.
                  */
                 if (event->rb == rb)
                         ring_buffer_attach(event, NULL);
 
                 mutex_unlock(&event->mmap_mutex);
                 put_event(event);
 
                 /*
                  * Restart the iteration; either we're on the wrong list or
                  * destroyed its integrity by doing a deletion.
                  */
                 goto again;
         }
         rcu_read_unlock();
 
         /*
          * It could be there's still a few 0-ref events on the list; they'll
          * get cleaned up by free_event() -- they'll also still have their
          * ref on the rb and will free it whenever they are done with it.
          *
          * Aside from that, this buffer is 'fully' detached and unmapped,
          * undo the VM accounting.
          */
 
         atomic_long_sub((size >> PAGE_SHIFT) + 1, &mmap_user->locked_vm);
         vma->vm_mm->pinned_vm -= mmap_locked;
         free_uid(mmap_user);
 
 out_put:
         ring_buffer_put(rb); /* could be last */
 }
 
 static const struct vm_operations_struct perf_mmap_vmops = {
         .open           = perf_mmap_open,
         .close          = perf_mmap_close, /* non mergable */
         .fault          = perf_mmap_fault,
         .page_mkwrite   = perf_mmap_fault,
 };
 
 static int perf_mmap(struct file *file, struct vm_area_struct *vma)
 {
         struct perf_event *event = file->private_data;
         unsigned long user_locked, user_lock_limit;
         struct user_struct *user = current_user();
         unsigned long locked, lock_limit;
         struct ring_buffer *rb = NULL;
         unsigned long vma_size;
         unsigned long nr_pages;
         long user_extra = 0, extra = 0;
         int ret = 0, flags = 0;
 
         /*
          * Don't allow mmap() of inherited per-task counters. This would
          * create a performance issue due to all children writing to the
          * same rb.
          */
         if (event->cpu == -1 && event->attr.inherit)
                 return -EINVAL;
 
         if (!(vma->vm_flags & VM_SHARED))
                 return -EINVAL;
 
         vma_size = vma->vm_end - vma->vm_start;
 
         if (vma->vm_pgoff == 0) {
                 nr_pages = (vma_size / PAGE_SIZE) - 1;
         } else {
                 /*
                  * AUX area mapping: if rb->aux_nr_pages != 0, it's already
                  * mapped, all subsequent mappings should have the same size
                  * and offset. Must be above the normal perf buffer.
                  */
                 u64 aux_offset, aux_size;
 
                 if (!event->rb)
                         return -EINVAL;
 
                 nr_pages = vma_size / PAGE_SIZE;
 
                 mutex_lock(&event->mmap_mutex);
                 ret = -EINVAL;
 
                 rb = event->rb;
                 if (!rb)
                         goto aux_unlock;
 
                 aux_offset = ACCESS_ONCE(rb->user_page->aux_offset);
                 aux_size = ACCESS_ONCE(rb->user_page->aux_size);
 
                 if (aux_offset < perf_data_size(rb) + PAGE_SIZE)
                         goto aux_unlock;
 
                 if (aux_offset != vma->vm_pgoff << PAGE_SHIFT)
                         goto aux_unlock;
 
                 /* already mapped with a different offset */
                 if (rb_has_aux(rb) && rb->aux_pgoff != vma->vm_pgoff)
                         goto aux_unlock;
 
                 if (aux_size != vma_size || aux_size != nr_pages * PAGE_SIZE)
                         goto aux_unlock;
 
                 /* already mapped with a different size */
                 if (rb_has_aux(rb) && rb->aux_nr_pages != nr_pages)
                         goto aux_unlock;
 
                 if (!is_power_of_2(nr_pages))
                         goto aux_unlock;
 
                 if (!atomic_inc_not_zero(&rb->mmap_count))
                         goto aux_unlock;
 
                 if (rb_has_aux(rb)) {
                         atomic_inc(&rb->aux_mmap_count);
                         ret = 0;
                         goto unlock;
                 }
 
                 atomic_set(&rb->aux_mmap_count, 1);
                 user_extra = nr_pages;
 
                 goto accounting;
         }
 
         /*
          * If we have rb pages ensure they're a power-of-two number, so we
          * can do bitmasks instead of modulo.
          */
         if (nr_pages != 0 && !is_power_of_2(nr_pages))
                 return -EINVAL;
 
         if (vma_size != PAGE_SIZE * (1 + nr_pages))
                 return -EINVAL;
 
         WARN_ON_ONCE(event->ctx->parent_ctx);
 again:
         mutex_lock(&event->mmap_mutex);
         if (event->rb) {
                 if (event->rb->nr_pages != nr_pages) {
                         ret = -EINVAL;
                         goto unlock;
                 }
 
                 if (!atomic_inc_not_zero(&event->rb->mmap_count)) {
                         /*
                          * Raced against perf_mmap_close() through
                          * perf_event_set_output(). Try again, hope for better
                          * luck.
                          */
                         mutex_unlock(&event->mmap_mutex);
                         goto again;
                 }
 
                 goto unlock;
         }
 
         user_extra = nr_pages + 1;
 
 accounting:
         user_lock_limit = sysctl_perf_event_mlock >> (PAGE_SHIFT - 10);
 
         /*
          * Increase the limit linearly with more CPUs:
          */
         user_lock_limit *= num_online_cpus();
 
         user_locked = atomic_long_read(&user->locked_vm) + user_extra;
 
         if (user_locked > user_lock_limit)
                 extra = user_locked - user_lock_limit;
 
         lock_limit = rlimit(RLIMIT_MEMLOCK);
         lock_limit >>= PAGE_SHIFT;
         locked = vma->vm_mm->pinned_vm + extra;
 
         if ((locked > lock_limit) && perf_paranoid_tracepoint_raw() &&
                 !capable(CAP_IPC_LOCK)) {
                 ret = -EPERM;
                 goto unlock;
         }
 
         WARN_ON(!rb && event->rb);
 
         if (vma->vm_flags & VM_WRITE)
                 flags |= RING_BUFFER_WRITABLE;
 
         if (!rb) {
                 rb = rb_alloc(nr_pages,
                               event->attr.watermark ? event->attr.wakeup_watermark : 0,
                               event->cpu, flags);
 
                 if (!rb) {
                         ret = -ENOMEM;
                         goto unlock;
                 }
 
                 atomic_set(&rb->mmap_count, 1);
                 rb->mmap_user = get_current_user();
                 rb->mmap_locked = extra;
 
                 ring_buffer_attach(event, rb);
 
                 perf_event_init_userpage(event);
                 perf_event_update_userpage(event);
         } else {
                 ret = rb_alloc_aux(rb, event, vma->vm_pgoff, nr_pages,
                                    event->attr.aux_watermark, flags);
                 if (!ret)
                         rb->aux_mmap_locked = extra;
         }
 
 unlock:
         if (!ret) {
                 atomic_long_add(user_extra, &user->locked_vm);
                 vma->vm_mm->pinned_vm += extra;
 
                 atomic_inc(&event->mmap_count);
         } else if (rb) {
                 atomic_dec(&rb->mmap_count);
         }
 aux_unlock:
         mutex_unlock(&event->mmap_mutex);
 
         /*
          * Since pinned accounting is per vm we cannot allow fork() to copy our
          * vma.
          */
         vma->vm_flags |= VM_DONTCOPY | VM_DONTEXPAND | VM_DONTDUMP;
         vma->vm_ops = &perf_mmap_vmops;
 
         if (event->pmu->event_mapped)
                 event->pmu->event_mapped(event);
 
         return ret;
 }
 
 static int perf_fasync(int fd, struct file *filp, int on)
 {
         struct inode *inode = file_inode(filp);
         struct perf_event *event = filp->private_data;
         int retval;
 
         inode_lock(inode);
         retval = fasync_helper(fd, filp, on, &event->fasync);
         inode_unlock(inode);
 
         if (retval < 0)
                 return retval;
 
         return 0;
 }
 
 static const struct file_operations perf_fops = {
         .llseek                 = no_llseek,
         .release                = perf_release,
         .read                   = perf_read,
         .poll                   = perf_poll,
         .unlocked_ioctl         = perf_ioctl,
         .compat_ioctl           = perf_compat_ioctl,
         .mmap                   = perf_mmap,
         .fasync                 = perf_fasync,
 };
 
 /*
  * Perf event wakeup
  *
  * If there's data, ensure we set the poll() state and publish everything
  * to user-space before waking everybody up.
  */
 
 static inline struct fasync_struct **perf_event_fasync(struct perf_event *event)
 {
         /* only the parent has fasync state */
         if (event->parent)
                 event = event->parent;
         return &event->fasync;
 }
 
 void perf_event_wakeup(struct perf_event *event)
 {
         ring_buffer_wakeup(event);
 
         if (event->pending_kill) {
                 kill_fasync(perf_event_fasync(event), SIGIO, event->pending_kill);
                 event->pending_kill = 0;
         }
 }
 
 static void perf_pending_event(struct irq_work *entry)
 {
         struct perf_event *event = container_of(entry,
                         struct perf_event, pending);
         int rctx;
 
         rctx = perf_swevent_get_recursion_context();
         /*
          * If we 'fail' here, that's OK, it means recursion is already disabled
          * and we won't recurse 'further'.
          */
 
         if (event->pending_disable) {
                 event->pending_disable = 0;
                 perf_event_disable_local(event);
         }
 
         if (event->pending_wakeup) {
                 event->pending_wakeup = 0;
                 perf_event_wakeup(event);
         }
 
         if (rctx >= 0)
                 perf_swevent_put_recursion_context(rctx);
 }
 
 /*
  * We assume there is only KVM supporting the callbacks.
  * Later on, we might change it to a list if there is
  * another virtualization implementation supporting the callbacks.
  */
 struct perf_guest_info_callbacks *perf_guest_cbs;
 
 int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
 {
         perf_guest_cbs = cbs;
         return 0;
 }
 EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
 
 int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
 {
         perf_guest_cbs = NULL;
         return 0;
 }
 EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
 
 static void
 perf_output_sample_regs(struct perf_output_handle *handle,
                         struct pt_regs *regs, u64 mask)
 {
         int bit;
 
         for_each_set_bit(bit, (const unsigned long *) &mask,
                          sizeof(mask) * BITS_PER_BYTE) {
                 u64 val;
 
                 val = perf_reg_value(regs, bit);
                 perf_output_put(handle, val);
         }
 }
 
 static void perf_sample_regs_user(struct perf_regs *regs_user,
                                   struct pt_regs *regs,
                                   struct pt_regs *regs_user_copy)
 {
         if (user_mode(regs)) {
                 regs_user->abi = perf_reg_abi(current);
                 regs_user->regs = regs;
         } else if (current->mm) {
                 perf_get_regs_user(regs_user, regs, regs_user_copy);
         } else {
                 regs_user->abi = PERF_SAMPLE_REGS_ABI_NONE;
                 regs_user->regs = NULL;
         }
 }
 
 static void perf_sample_regs_intr(struct perf_regs *regs_intr,
                                   struct pt_regs *regs)
 {
         regs_intr->regs = regs;
         regs_intr->abi  = perf_reg_abi(current);
 }
 
 
 /*
  * Get remaining task size from user stack pointer.
  *
  * It'd be better to take stack vma map and limit this more
  * precisly, but there's no way to get it safely under interrupt,
  * so using TASK_SIZE as limit.
  */
 static u64 perf_ustack_task_size(struct pt_regs *regs)
 {
         unsigned long addr = perf_user_stack_pointer(regs);
 
         if (!addr || addr >= TASK_SIZE)
                 return 0;
 
         return TASK_SIZE - addr;
 }
 
 static u16
 perf_sample_ustack_size(u16 stack_size, u16 header_size,
                         struct pt_regs *regs)
 {
         u64 task_size;
 
         /* No regs, no stack pointer, no dump. */
         if (!regs)
                 return 0;
 
         /*
          * Check if we fit in with the requested stack size into the:
          * - TASK_SIZE
          *   If we don't, we limit the size to the TASK_SIZE.
          *
          * - remaining sample size
          *   If we don't, we customize the stack size to
          *   fit in to the remaining sample size.
          */
 
         task_size  = min((u64) USHRT_MAX, perf_ustack_task_size(regs));
         stack_size = min(stack_size, (u16) task_size);
 
         /* Current header size plus static size and dynamic size. */
         header_size += 2 * sizeof(u64);
 
         /* Do we fit in with the current stack dump size? */
         if ((u16) (header_size + stack_size) < header_size) {
                 /*
                  * If we overflow the maximum size for the sample,
                  * we customize the stack dump size to fit in.
                  */
                 stack_size = USHRT_MAX - header_size - sizeof(u64);
                 stack_size = round_up(stack_size, sizeof(u64));
         }
 
         return stack_size;
 }
 
 static void
 perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
                           struct pt_regs *regs)
 {
         /* Case of a kernel thread, nothing to dump */
         if (!regs) {
                 u64 size = 0;
                 perf_output_put(handle, size);
         } else {
                 unsigned long sp;
                 unsigned int rem;
                 u64 dyn_size;
 
                 /*
                  * We dump:
                  * static size
                  *   - the size requested by user or the best one we can fit
                  *     in to the sample max size
                  * data
                  *   - user stack dump data
                  * dynamic size
                  *   - the actual dumped size
                  */
 
                 /* Static size. */
                 perf_output_put(handle, dump_size);
 
                 /* Data. */
                 sp = perf_user_stack_pointer(regs);
                 rem = __output_copy_user(handle, (void *) sp, dump_size);
                 dyn_size = dump_size - rem;
 
                 perf_output_skip(handle, rem);
 
                 /* Dynamic size. */
                 perf_output_put(handle, dyn_size);
         }
 }
 
 static void __perf_event_header__init_id(struct perf_event_header *header,
                                          struct perf_sample_data *data,
                                          struct perf_event *event)
 {
         u64 sample_type = event->attr.sample_type;
 
         data->type = sample_type;
         header->size += event->id_header_size;
 
         if (sample_type & PERF_SAMPLE_TID) {
                 /* namespace issues */
                 data->tid_entry.pid = perf_event_pid(event, current);
                 data->tid_entry.tid = perf_event_tid(event, current);
         }
 
         if (sample_type & PERF_SAMPLE_TIME)
                 data->time = perf_event_clock(event);
 
         if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER))
                 data->id = primary_event_id(event);
 
         if (sample_type & PERF_SAMPLE_STREAM_ID)
                 data->stream_id = event->id;
 
         if (sample_type & PERF_SAMPLE_CPU) {
                 data->cpu_entry.cpu      = raw_smp_processor_id();
                 data->cpu_entry.reserved = 0;
         }
 }
 
 void perf_event_header__init_id(struct perf_event_header *header,
                                 struct perf_sample_data *data,
                                 struct perf_event *event)
 {
         if (event->attr.sample_id_all)
                 __perf_event_header__init_id(header, data, event);
 }
 
 static void __perf_event__output_id_sample(struct perf_output_handle *handle,
                                            struct perf_sample_data *data)
 {
         u64 sample_type = data->type;
 
         if (sample_type & PERF_SAMPLE_TID)
                 perf_output_put(handle, data->tid_entry);
 
         if (sample_type & PERF_SAMPLE_TIME)
                 perf_output_put(handle, data->time);
 
         if (sample_type & PERF_SAMPLE_ID)
                 perf_output_put(handle, data->id);
 
         if (sample_type & PERF_SAMPLE_STREAM_ID)
                 perf_output_put(handle, data->stream_id);
 
         if (sample_type & PERF_SAMPLE_CPU)
                 perf_output_put(handle, data->cpu_entry);
 
         if (sample_type & PERF_SAMPLE_IDENTIFIER)
                 perf_output_put(handle, data->id);
 }
 
 void perf_event__output_id_sample(struct perf_event *event,
                                   struct perf_output_handle *handle,
                                   struct perf_sample_data *sample)
 {
         if (event->attr.sample_id_all)
                 __perf_event__output_id_sample(handle, sample);
 }
 
 static void perf_output_read_one(struct perf_output_handle *handle,
                                  struct perf_event *event,
                                  u64 enabled, u64 running)
 {
         u64 read_format = event->attr.read_format;
         u64 values[4];
         int n = 0;
 
         values[n++] = perf_event_count(event);
         if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {
                 values[n++] = enabled +
                         atomic64_read(&event->child_total_time_enabled);
         }
         if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {
                 values[n++] = running +
                         atomic64_read(&event->child_total_time_running);
         }
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(event);
 
         __output_copy(handle, values, n * sizeof(u64));
 }
 
 /*
  * XXX PERF_FORMAT_GROUP vs inherited events seems difficult.
  */
 static void perf_output_read_group(struct perf_output_handle *handle,
                             struct perf_event *event,
                             u64 enabled, u64 running)
 {
         struct perf_event *leader = event->group_leader, *sub;
         u64 read_format = event->attr.read_format;
         u64 values[5];
         int n = 0;
 
         values[n++] = 1 + leader->nr_siblings;
 
         if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
                 values[n++] = enabled;
 
         if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
                 values[n++] = running;
 
         if (leader != event)
                 leader->pmu->read(leader);
 
         values[n++] = perf_event_count(leader);
         if (read_format & PERF_FORMAT_ID)
                 values[n++] = primary_event_id(leader);
 
         __output_copy(handle, values, n * sizeof(u64));
 
         list_for_each_entry(sub, &leader->sibling_list, group_entry) {
                 n = 0;
 
                 if ((sub != event) &&
                     (sub->state == PERF_EVENT_STATE_ACTIVE))
                         sub->pmu->read(sub);
 
                 values[n++] = perf_event_count(sub);
                 if (read_format & PERF_FORMAT_ID)
                         values[n++] = primary_event_id(sub);
 
                 __output_copy(handle, values, n * sizeof(u64));
         }
 }
 
 #define PERF_FORMAT_TOTAL_TIMES (PERF_FORMAT_TOTAL_TIME_ENABLED|\
                                  PERF_FORMAT_TOTAL_TIME_RUNNING)
 
 static void perf_output_read(struct perf_output_handle *handle,
                              struct perf_event *event)
 {
         u64 enabled = 0, running = 0, now;
         u64 read_format = event->attr.read_format;
 
         /*
          * compute total_time_enabled, total_time_running
          * based on snapshot values taken when the event
          * was last scheduled in.
          *
          * we cannot simply called update_context_time()
          * because of locking issue as we are called in
          * NMI context
          */
         if (read_format & PERF_FORMAT_TOTAL_TIMES)
                 calc_timer_values(event, &now, &enabled, &running);
 
         if (event->attr.read_format & PERF_FORMAT_GROUP)
                 perf_output_read_group(handle, event, enabled, running);
         else
                 perf_output_read_one(handle, event, enabled, running);
 }
 
 void perf_output_sample(struct perf_output_handle *handle,
                         struct perf_event_header *header,
                         struct perf_sample_data *data,
                         struct perf_event *event)
 {
         u64 sample_type = data->type;
 
         perf_output_put(handle, *header);
 
         if (sample_type & PERF_SAMPLE_IDENTIFIER)
                 perf_output_put(handle, data->id);
 
         if (sample_type & PERF_SAMPLE_IP)
                 perf_output_put(handle, data->ip);
 
         if (sample_type & PERF_SAMPLE_TID)
                 perf_output_put(handle, data->tid_entry);
 
         if (sample_type & PERF_SAMPLE_TIME)
                 perf_output_put(handle, data->time);
 
         if (sample_type & PERF_SAMPLE_ADDR)
                 perf_output_put(handle, data->addr);
 
         if (sample_type & PERF_SAMPLE_ID)
                 perf_output_put(handle, data->id);
 
         if (sample_type & PERF_SAMPLE_STREAM_ID)
                 perf_output_put(handle, data->stream_id);
 
         if (sample_type & PERF_SAMPLE_CPU)
                 perf_output_put(handle, data->cpu_entry);
 
         if (sample_type & PERF_SAMPLE_PERIOD)
                 perf_output_put(handle, data->period);
 
         if (sample_type & PERF_SAMPLE_READ)
                 perf_output_read(handle, event);
 
         if (sample_type & PERF_SAMPLE_CALLCHAIN) {
                 if (data->callchain) {
                         int size = 1;
 
                         if (data->callchain)
                                 size += data->callchain->nr;
 
                         size *= sizeof(u64);
 
                         __output_copy(handle, data->callchain, size);
                 } else {
                         u64 nr = 0;
                         perf_output_put(handle, nr);
                 }
         }
 
         if (sample_type & PERF_SAMPLE_RAW) {
                 if (data->raw) {
                         u32 raw_size = data->raw->size;
                         u32 real_size = round_up(raw_size + sizeof(u32),
                                                  sizeof(u64)) - sizeof(u32);
                         u64 zero = 0;
 
                         perf_output_put(handle, real_size);
                         __output_copy(handle, data->raw->data, raw_size);
                         if (real_size - raw_size)
                                 __output_copy(handle, &zero, real_size - raw_size);
                 } else {
                         struct {
                                 u32     size;
                                 u32     data;
                         } raw = {
                                 .size = sizeof(u32),
                                 .data = 0,
                         };
                         perf_output_put(handle, raw);
                 }
         }
 
         if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
                 if (data->br_stack) {
                         size_t size;
 
                         size = data->br_stack->nr
                              * sizeof(struct perf_branch_entry);
 
                         perf_output_put(handle, data->br_stack->nr);
                         perf_output_copy(handle, data->br_stack->entries, size);
                 } else {
                         /*
                          * we always store at least the value of nr
                          */
                         u64 nr = 0;
                         perf_output_put(handle, nr);
                 }
         }
 
         if (sample_type & PERF_SAMPLE_REGS_USER) {
                 u64 abi = data->regs_user.abi;
 
                 /*
                  * If there are no regs to dump, notice it through
                  * first u64 being zero (PERF_SAMPLE_REGS_ABI_NONE).
                  */
                 perf_output_put(handle, abi);
 
                 if (abi) {
                         u64 mask = event->attr.sample_regs_user;
                         perf_output_sample_regs(handle,
                                                 data->regs_user.regs,
                                                 mask);
                 }
         }
 
         if (sample_type & PERF_SAMPLE_STACK_USER) {
                 perf_output_sample_ustack(handle,
                                           data->stack_user_size,
                                           data->regs_user.regs);
         }
 
         if (sample_type & PERF_SAMPLE_WEIGHT)
                 perf_output_put(handle, data->weight);
 
         if (sample_type & PERF_SAMPLE_DATA_SRC)
                 perf_output_put(handle, data->data_src.val);
 
         if (sample_type & PERF_SAMPLE_TRANSACTION)
                 perf_output_put(handle, data->txn);
 
         if (sample_type & PERF_SAMPLE_REGS_INTR) {
                 u64 abi = data->regs_intr.abi;
                 /*
                  * If there are no regs to dump, notice it through
                  * first u64 being zero (PERF_SAMPLE_REGS_ABI_NONE).
                  */
                 perf_output_put(handle, abi);
 
                 if (abi) {
                         u64 mask = event->attr.sample_regs_intr;
 
                         perf_output_sample_regs(handle,
                                                 data->regs_intr.regs,
                                                 mask);
                 }
         }
 
         if (!event->attr.watermark) {
                 int wakeup_events = event->attr.wakeup_events;
 
                 if (wakeup_events) {
                         struct ring_buffer *rb = handle->rb;
                         int events = local_inc_return(&rb->events);
 
                         if (events >= wakeup_events) {
                                 local_sub(wakeup_events, &rb->events);
                                 local_inc(&rb->wakeup);
                         }
                 }
         }
 }
 
 void perf_prepare_sample(struct perf_event_header *header,
                          struct perf_sample_data *data,
                          struct perf_event *event,
                          struct pt_regs *regs)
 {
         u64 sample_type = event->attr.sample_type;
 
         header->type = PERF_RECORD_SAMPLE;
         header->size = sizeof(*header) + event->header_size;
 
         header->misc = 0;
         header->misc |= perf_misc_flags(regs);
 
         __perf_event_header__init_id(header, data, event);
 
         if (sample_type & PERF_SAMPLE_IP)
                 data->ip = perf_instruction_pointer(regs);
 
         if (sample_type & PERF_SAMPLE_CALLCHAIN) {
                 int size = 1;
 
                 data->callchain = perf_callchain(event, regs);
 
                 if (data->callchain)
                         size += data->callchain->nr;
 
                 header->size += size * sizeof(u64);
         }
 
         if (sample_type & PERF_SAMPLE_RAW) {
                 int size = sizeof(u32);
 
                 if (data->raw)
                         size += data->raw->size;
                 else
                         size += sizeof(u32);
 
                 header->size += round_up(size, sizeof(u64));
         }
 
         if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
                 int size = sizeof(u64); /* nr */
                 if (data->br_stack) {
                         size += data->br_stack->nr
                               * sizeof(struct perf_branch_entry);
                 }
                 header->size += size;
         }
 
         if (sample_type & (PERF_SAMPLE_REGS_USER | PERF_SAMPLE_STACK_USER))
                 perf_sample_regs_user(&data->regs_user, regs,
                                       &data->regs_user_copy);
 
         if (sample_type & PERF_SAMPLE_REGS_USER) {
                 /* regs dump ABI info */
                 int size = sizeof(u64);
 
                 if (data->regs_user.regs) {
                         u64 mask = event->attr.sample_regs_user;
                         size += hweight64(mask) * sizeof(u64);
                 }
 
                 header->size += size;
         }
 
         if (sample_type & PERF_SAMPLE_STACK_USER) {
                 /*
                  * Either we need PERF_SAMPLE_STACK_USER bit to be allways
                  * processed as the last one or have additional check added
                  * in case new sample type is added, because we could eat
                  * up the rest of the sample size.
                  */
                 u16 stack_size = event->attr.sample_stack_user;
                 u16 size = sizeof(u64);
 
                 stack_size = perf_sample_ustack_size(stack_size, header->size,
                                                      data->regs_user.regs);
 
                 /*
                  * If there is something to dump, add space for the dump
                  * itself and for the field that tells the dynamic size,
                  * which is how many have been actually dumped.
                  */
                 if (stack_size)
                         size += sizeof(u64) + stack_size;
 
                 data->stack_user_size = stack_size;
                 header->size += size;
         }
 
         if (sample_type & PERF_SAMPLE_REGS_INTR) {
                 /* regs dump ABI info */
                 int size = sizeof(u64);
 
                 perf_sample_regs_intr(&data->regs_intr, regs);
 
                 if (data->regs_intr.regs) {
                         u64 mask = event->attr.sample_regs_intr;
 
                         size += hweight64(mask) * sizeof(u64);
                 }
 
                 header->size += size;
         }
 }
 
 static void __always_inline
 __perf_event_output(struct perf_event *event,
                     struct perf_sample_data *data,
                     struct pt_regs *regs,
                     int (*output_begin)(struct perf_output_handle *,
                                         struct perf_event *,
                                         unsigned int))
 {
         struct perf_output_handle handle;
         struct perf_event_header header;
 
         /* protect the callchain buffers */
         rcu_read_lock();
 
         perf_prepare_sample(&header, data, event, regs);
 
         if (output_begin(&handle, event, header.size))
                 goto exit;
 
         perf_output_sample(&handle, &header, data, event);
 
         perf_output_end(&handle);
 
 exit:
         rcu_read_unlock();
 }
 
 void
 perf_event_output_forward(struct perf_event *event,
                          struct perf_sample_data *data,
                          struct pt_regs *regs)
 {
         __perf_event_output(event, data, regs, perf_output_begin_forward);
 }
 
 void
 perf_event_output_backward(struct perf_event *event,
                            struct perf_sample_data *data,