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TOMOYO Linux Cross Reference
Linux/kernel/trace/trace_sched_wakeup.c

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  1 /*
  2  * trace task wakeup timings
  3  *
  4  * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
  5  * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
  6  *
  7  * Based on code from the latency_tracer, that is:
  8  *
  9  *  Copyright (C) 2004-2006 Ingo Molnar
 10  *  Copyright (C) 2004 William Lee Irwin III
 11  */
 12 #include <linux/module.h>
 13 #include <linux/fs.h>
 14 #include <linux/debugfs.h>
 15 #include <linux/kallsyms.h>
 16 #include <linux/uaccess.h>
 17 #include <linux/ftrace.h>
 18 #include <trace/events/sched.h>
 19 
 20 #include "trace.h"
 21 
 22 static struct trace_array       *wakeup_trace;
 23 static int __read_mostly        tracer_enabled;
 24 
 25 static struct task_struct       *wakeup_task;
 26 static int                      wakeup_cpu;
 27 static int                      wakeup_current_cpu;
 28 static unsigned                 wakeup_prio = -1;
 29 static int                      wakeup_rt;
 30 
 31 static arch_spinlock_t wakeup_lock =
 32         (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
 33 
 34 static void wakeup_reset(struct trace_array *tr);
 35 static void __wakeup_reset(struct trace_array *tr);
 36 static int wakeup_graph_entry(struct ftrace_graph_ent *trace);
 37 static void wakeup_graph_return(struct ftrace_graph_ret *trace);
 38 
 39 static int save_flags;
 40 
 41 #define TRACE_DISPLAY_GRAPH     1
 42 
 43 static struct tracer_opt trace_opts[] = {
 44 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
 45         /* display latency trace as call graph */
 46         { TRACER_OPT(display-graph, TRACE_DISPLAY_GRAPH) },
 47 #endif
 48         { } /* Empty entry */
 49 };
 50 
 51 static struct tracer_flags tracer_flags = {
 52         .val  = 0,
 53         .opts = trace_opts,
 54 };
 55 
 56 #define is_graph() (tracer_flags.val & TRACE_DISPLAY_GRAPH)
 57 
 58 #ifdef CONFIG_FUNCTION_TRACER
 59 
 60 /*
 61  * Prologue for the wakeup function tracers.
 62  *
 63  * Returns 1 if it is OK to continue, and preemption
 64  *            is disabled and data->disabled is incremented.
 65  *         0 if the trace is to be ignored, and preemption
 66  *            is not disabled and data->disabled is
 67  *            kept the same.
 68  *
 69  * Note, this function is also used outside this ifdef but
 70  *  inside the #ifdef of the function graph tracer below.
 71  *  This is OK, since the function graph tracer is
 72  *  dependent on the function tracer.
 73  */
 74 static int
 75 func_prolog_preempt_disable(struct trace_array *tr,
 76                             struct trace_array_cpu **data,
 77                             int *pc)
 78 {
 79         long disabled;
 80         int cpu;
 81 
 82         if (likely(!wakeup_task))
 83                 return 0;
 84 
 85         *pc = preempt_count();
 86         preempt_disable_notrace();
 87 
 88         cpu = raw_smp_processor_id();
 89         if (cpu != wakeup_current_cpu)
 90                 goto out_enable;
 91 
 92         *data = tr->data[cpu];
 93         disabled = atomic_inc_return(&(*data)->disabled);
 94         if (unlikely(disabled != 1))
 95                 goto out;
 96 
 97         return 1;
 98 
 99 out:
100         atomic_dec(&(*data)->disabled);
101 
102 out_enable:
103         preempt_enable_notrace();
104         return 0;
105 }
106 
107 /*
108  * wakeup uses its own tracer function to keep the overhead down:
109  */
110 static void
111 wakeup_tracer_call(unsigned long ip, unsigned long parent_ip)
112 {
113         struct trace_array *tr = wakeup_trace;
114         struct trace_array_cpu *data;
115         unsigned long flags;
116         int pc;
117 
118         if (!func_prolog_preempt_disable(tr, &data, &pc))
119                 return;
120 
121         local_irq_save(flags);
122         trace_function(tr, ip, parent_ip, flags, pc);
123         local_irq_restore(flags);
124 
125         atomic_dec(&data->disabled);
126         preempt_enable_notrace();
127 }
128 
129 static struct ftrace_ops trace_ops __read_mostly =
130 {
131         .func = wakeup_tracer_call,
132         .flags = FTRACE_OPS_FL_GLOBAL,
133 };
134 #endif /* CONFIG_FUNCTION_TRACER */
135 
136 static int start_func_tracer(int graph)
137 {
138         int ret;
139 
140         if (!graph)
141                 ret = register_ftrace_function(&trace_ops);
142         else
143                 ret = register_ftrace_graph(&wakeup_graph_return,
144                                             &wakeup_graph_entry);
145 
146         if (!ret && tracing_is_enabled())
147                 tracer_enabled = 1;
148         else
149                 tracer_enabled = 0;
150 
151         return ret;
152 }
153 
154 static void stop_func_tracer(int graph)
155 {
156         tracer_enabled = 0;
157 
158         if (!graph)
159                 unregister_ftrace_function(&trace_ops);
160         else
161                 unregister_ftrace_graph();
162 }
163 
164 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
165 static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
166 {
167 
168         if (!(bit & TRACE_DISPLAY_GRAPH))
169                 return -EINVAL;
170 
171         if (!(is_graph() ^ set))
172                 return 0;
173 
174         stop_func_tracer(!set);
175 
176         wakeup_reset(wakeup_trace);
177         tracing_max_latency = 0;
178 
179         return start_func_tracer(set);
180 }
181 
182 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
183 {
184         struct trace_array *tr = wakeup_trace;
185         struct trace_array_cpu *data;
186         unsigned long flags;
187         int pc, ret = 0;
188 
189         if (!func_prolog_preempt_disable(tr, &data, &pc))
190                 return 0;
191 
192         local_save_flags(flags);
193         ret = __trace_graph_entry(tr, trace, flags, pc);
194         atomic_dec(&data->disabled);
195         preempt_enable_notrace();
196 
197         return ret;
198 }
199 
200 static void wakeup_graph_return(struct ftrace_graph_ret *trace)
201 {
202         struct trace_array *tr = wakeup_trace;
203         struct trace_array_cpu *data;
204         unsigned long flags;
205         int pc;
206 
207         if (!func_prolog_preempt_disable(tr, &data, &pc))
208                 return;
209 
210         local_save_flags(flags);
211         __trace_graph_return(tr, trace, flags, pc);
212         atomic_dec(&data->disabled);
213 
214         preempt_enable_notrace();
215         return;
216 }
217 
218 static void wakeup_trace_open(struct trace_iterator *iter)
219 {
220         if (is_graph())
221                 graph_trace_open(iter);
222 }
223 
224 static void wakeup_trace_close(struct trace_iterator *iter)
225 {
226         if (iter->private)
227                 graph_trace_close(iter);
228 }
229 
230 #define GRAPH_TRACER_FLAGS (TRACE_GRAPH_PRINT_PROC)
231 
232 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
233 {
234         /*
235          * In graph mode call the graph tracer output function,
236          * otherwise go with the TRACE_FN event handler
237          */
238         if (is_graph())
239                 return print_graph_function_flags(iter, GRAPH_TRACER_FLAGS);
240 
241         return TRACE_TYPE_UNHANDLED;
242 }
243 
244 static void wakeup_print_header(struct seq_file *s)
245 {
246         if (is_graph())
247                 print_graph_headers_flags(s, GRAPH_TRACER_FLAGS);
248         else
249                 trace_default_header(s);
250 }
251 
252 static void
253 __trace_function(struct trace_array *tr,
254                  unsigned long ip, unsigned long parent_ip,
255                  unsigned long flags, int pc)
256 {
257         if (is_graph())
258                 trace_graph_function(tr, ip, parent_ip, flags, pc);
259         else
260                 trace_function(tr, ip, parent_ip, flags, pc);
261 }
262 #else
263 #define __trace_function trace_function
264 
265 static int wakeup_set_flag(u32 old_flags, u32 bit, int set)
266 {
267         return -EINVAL;
268 }
269 
270 static int wakeup_graph_entry(struct ftrace_graph_ent *trace)
271 {
272         return -1;
273 }
274 
275 static enum print_line_t wakeup_print_line(struct trace_iterator *iter)
276 {
277         return TRACE_TYPE_UNHANDLED;
278 }
279 
280 static void wakeup_graph_return(struct ftrace_graph_ret *trace) { }
281 static void wakeup_print_header(struct seq_file *s) { }
282 static void wakeup_trace_open(struct trace_iterator *iter) { }
283 static void wakeup_trace_close(struct trace_iterator *iter) { }
284 #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
285 
286 /*
287  * Should this new latency be reported/recorded?
288  */
289 static int report_latency(cycle_t delta)
290 {
291         if (tracing_thresh) {
292                 if (delta < tracing_thresh)
293                         return 0;
294         } else {
295                 if (delta <= tracing_max_latency)
296                         return 0;
297         }
298         return 1;
299 }
300 
301 static void
302 probe_wakeup_migrate_task(void *ignore, struct task_struct *task, int cpu)
303 {
304         if (task != wakeup_task)
305                 return;
306 
307         wakeup_current_cpu = cpu;
308 }
309 
310 static void notrace
311 probe_wakeup_sched_switch(void *ignore,
312                           struct task_struct *prev, struct task_struct *next)
313 {
314         struct trace_array_cpu *data;
315         cycle_t T0, T1, delta;
316         unsigned long flags;
317         long disabled;
318         int cpu;
319         int pc;
320 
321         tracing_record_cmdline(prev);
322 
323         if (unlikely(!tracer_enabled))
324                 return;
325 
326         /*
327          * When we start a new trace, we set wakeup_task to NULL
328          * and then set tracer_enabled = 1. We want to make sure
329          * that another CPU does not see the tracer_enabled = 1
330          * and the wakeup_task with an older task, that might
331          * actually be the same as next.
332          */
333         smp_rmb();
334 
335         if (next != wakeup_task)
336                 return;
337 
338         pc = preempt_count();
339 
340         /* disable local data, not wakeup_cpu data */
341         cpu = raw_smp_processor_id();
342         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
343         if (likely(disabled != 1))
344                 goto out;
345 
346         local_irq_save(flags);
347         arch_spin_lock(&wakeup_lock);
348 
349         /* We could race with grabbing wakeup_lock */
350         if (unlikely(!tracer_enabled || next != wakeup_task))
351                 goto out_unlock;
352 
353         /* The task we are waiting for is waking up */
354         data = wakeup_trace->data[wakeup_cpu];
355 
356         __trace_function(wakeup_trace, CALLER_ADDR0, CALLER_ADDR1, flags, pc);
357         tracing_sched_switch_trace(wakeup_trace, prev, next, flags, pc);
358 
359         T0 = data->preempt_timestamp;
360         T1 = ftrace_now(cpu);
361         delta = T1-T0;
362 
363         if (!report_latency(delta))
364                 goto out_unlock;
365 
366         if (likely(!is_tracing_stopped())) {
367                 tracing_max_latency = delta;
368                 update_max_tr(wakeup_trace, wakeup_task, wakeup_cpu);
369         }
370 
371 out_unlock:
372         __wakeup_reset(wakeup_trace);
373         arch_spin_unlock(&wakeup_lock);
374         local_irq_restore(flags);
375 out:
376         atomic_dec(&wakeup_trace->data[cpu]->disabled);
377 }
378 
379 static void __wakeup_reset(struct trace_array *tr)
380 {
381         wakeup_cpu = -1;
382         wakeup_prio = -1;
383 
384         if (wakeup_task)
385                 put_task_struct(wakeup_task);
386 
387         wakeup_task = NULL;
388 }
389 
390 static void wakeup_reset(struct trace_array *tr)
391 {
392         unsigned long flags;
393 
394         tracing_reset_online_cpus(tr);
395 
396         local_irq_save(flags);
397         arch_spin_lock(&wakeup_lock);
398         __wakeup_reset(tr);
399         arch_spin_unlock(&wakeup_lock);
400         local_irq_restore(flags);
401 }
402 
403 static void
404 probe_wakeup(void *ignore, struct task_struct *p, int success)
405 {
406         struct trace_array_cpu *data;
407         int cpu = smp_processor_id();
408         unsigned long flags;
409         long disabled;
410         int pc;
411 
412         if (likely(!tracer_enabled))
413                 return;
414 
415         tracing_record_cmdline(p);
416         tracing_record_cmdline(current);
417 
418         if ((wakeup_rt && !rt_task(p)) ||
419                         p->prio >= wakeup_prio ||
420                         p->prio >= current->prio)
421                 return;
422 
423         pc = preempt_count();
424         disabled = atomic_inc_return(&wakeup_trace->data[cpu]->disabled);
425         if (unlikely(disabled != 1))
426                 goto out;
427 
428         /* interrupts should be off from try_to_wake_up */
429         arch_spin_lock(&wakeup_lock);
430 
431         /* check for races. */
432         if (!tracer_enabled || p->prio >= wakeup_prio)
433                 goto out_locked;
434 
435         /* reset the trace */
436         __wakeup_reset(wakeup_trace);
437 
438         wakeup_cpu = task_cpu(p);
439         wakeup_current_cpu = wakeup_cpu;
440         wakeup_prio = p->prio;
441 
442         wakeup_task = p;
443         get_task_struct(wakeup_task);
444 
445         local_save_flags(flags);
446 
447         data = wakeup_trace->data[wakeup_cpu];
448         data->preempt_timestamp = ftrace_now(cpu);
449         tracing_sched_wakeup_trace(wakeup_trace, p, current, flags, pc);
450 
451         /*
452          * We must be careful in using CALLER_ADDR2. But since wake_up
453          * is not called by an assembly function  (where as schedule is)
454          * it should be safe to use it here.
455          */
456         __trace_function(wakeup_trace, CALLER_ADDR1, CALLER_ADDR2, flags, pc);
457 
458 out_locked:
459         arch_spin_unlock(&wakeup_lock);
460 out:
461         atomic_dec(&wakeup_trace->data[cpu]->disabled);
462 }
463 
464 static void start_wakeup_tracer(struct trace_array *tr)
465 {
466         int ret;
467 
468         ret = register_trace_sched_wakeup(probe_wakeup, NULL);
469         if (ret) {
470                 pr_info("wakeup trace: Couldn't activate tracepoint"
471                         " probe to kernel_sched_wakeup\n");
472                 return;
473         }
474 
475         ret = register_trace_sched_wakeup_new(probe_wakeup, NULL);
476         if (ret) {
477                 pr_info("wakeup trace: Couldn't activate tracepoint"
478                         " probe to kernel_sched_wakeup_new\n");
479                 goto fail_deprobe;
480         }
481 
482         ret = register_trace_sched_switch(probe_wakeup_sched_switch, NULL);
483         if (ret) {
484                 pr_info("sched trace: Couldn't activate tracepoint"
485                         " probe to kernel_sched_switch\n");
486                 goto fail_deprobe_wake_new;
487         }
488 
489         ret = register_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
490         if (ret) {
491                 pr_info("wakeup trace: Couldn't activate tracepoint"
492                         " probe to kernel_sched_migrate_task\n");
493                 return;
494         }
495 
496         wakeup_reset(tr);
497 
498         /*
499          * Don't let the tracer_enabled = 1 show up before
500          * the wakeup_task is reset. This may be overkill since
501          * wakeup_reset does a spin_unlock after setting the
502          * wakeup_task to NULL, but I want to be safe.
503          * This is a slow path anyway.
504          */
505         smp_wmb();
506 
507         if (start_func_tracer(is_graph()))
508                 printk(KERN_ERR "failed to start wakeup tracer\n");
509 
510         return;
511 fail_deprobe_wake_new:
512         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
513 fail_deprobe:
514         unregister_trace_sched_wakeup(probe_wakeup, NULL);
515 }
516 
517 static void stop_wakeup_tracer(struct trace_array *tr)
518 {
519         tracer_enabled = 0;
520         stop_func_tracer(is_graph());
521         unregister_trace_sched_switch(probe_wakeup_sched_switch, NULL);
522         unregister_trace_sched_wakeup_new(probe_wakeup, NULL);
523         unregister_trace_sched_wakeup(probe_wakeup, NULL);
524         unregister_trace_sched_migrate_task(probe_wakeup_migrate_task, NULL);
525 }
526 
527 static int __wakeup_tracer_init(struct trace_array *tr)
528 {
529         save_flags = trace_flags;
530 
531         /* non overwrite screws up the latency tracers */
532         set_tracer_flag(TRACE_ITER_OVERWRITE, 1);
533         set_tracer_flag(TRACE_ITER_LATENCY_FMT, 1);
534 
535         tracing_max_latency = 0;
536         wakeup_trace = tr;
537         start_wakeup_tracer(tr);
538         return 0;
539 }
540 
541 static int wakeup_tracer_init(struct trace_array *tr)
542 {
543         wakeup_rt = 0;
544         return __wakeup_tracer_init(tr);
545 }
546 
547 static int wakeup_rt_tracer_init(struct trace_array *tr)
548 {
549         wakeup_rt = 1;
550         return __wakeup_tracer_init(tr);
551 }
552 
553 static void wakeup_tracer_reset(struct trace_array *tr)
554 {
555         int lat_flag = save_flags & TRACE_ITER_LATENCY_FMT;
556         int overwrite_flag = save_flags & TRACE_ITER_OVERWRITE;
557 
558         stop_wakeup_tracer(tr);
559         /* make sure we put back any tasks we are tracing */
560         wakeup_reset(tr);
561 
562         set_tracer_flag(TRACE_ITER_LATENCY_FMT, lat_flag);
563         set_tracer_flag(TRACE_ITER_OVERWRITE, overwrite_flag);
564 }
565 
566 static void wakeup_tracer_start(struct trace_array *tr)
567 {
568         wakeup_reset(tr);
569         tracer_enabled = 1;
570 }
571 
572 static void wakeup_tracer_stop(struct trace_array *tr)
573 {
574         tracer_enabled = 0;
575 }
576 
577 static struct tracer wakeup_tracer __read_mostly =
578 {
579         .name           = "wakeup",
580         .init           = wakeup_tracer_init,
581         .reset          = wakeup_tracer_reset,
582         .start          = wakeup_tracer_start,
583         .stop           = wakeup_tracer_stop,
584         .print_max      = 1,
585         .print_header   = wakeup_print_header,
586         .print_line     = wakeup_print_line,
587         .flags          = &tracer_flags,
588         .set_flag       = wakeup_set_flag,
589         .flag_changed   = trace_keep_overwrite,
590 #ifdef CONFIG_FTRACE_SELFTEST
591         .selftest    = trace_selftest_startup_wakeup,
592 #endif
593         .open           = wakeup_trace_open,
594         .close          = wakeup_trace_close,
595         .use_max_tr     = 1,
596 };
597 
598 static struct tracer wakeup_rt_tracer __read_mostly =
599 {
600         .name           = "wakeup_rt",
601         .init           = wakeup_rt_tracer_init,
602         .reset          = wakeup_tracer_reset,
603         .start          = wakeup_tracer_start,
604         .stop           = wakeup_tracer_stop,
605         .wait_pipe      = poll_wait_pipe,
606         .print_max      = 1,
607         .print_header   = wakeup_print_header,
608         .print_line     = wakeup_print_line,
609         .flags          = &tracer_flags,
610         .set_flag       = wakeup_set_flag,
611         .flag_changed   = trace_keep_overwrite,
612 #ifdef CONFIG_FTRACE_SELFTEST
613         .selftest    = trace_selftest_startup_wakeup,
614 #endif
615         .open           = wakeup_trace_open,
616         .close          = wakeup_trace_close,
617         .use_max_tr     = 1,
618 };
619 
620 __init static int init_wakeup_tracer(void)
621 {
622         int ret;
623 
624         ret = register_tracer(&wakeup_tracer);
625         if (ret)
626                 return ret;
627 
628         ret = register_tracer(&wakeup_rt_tracer);
629         if (ret)
630                 return ret;
631 
632         return 0;
633 }
634 device_initcall(init_wakeup_tracer);
635 

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