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Linux/kernel/locking/rtmutex-debug.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * RT-Mutexes: blocking mutual exclusion locks with PI support
  4  *
  5  * started by Ingo Molnar and Thomas Gleixner:
  6  *
  7  *  Copyright (C) 2004-2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
  8  *  Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
  9  *
 10  * This code is based on the rt.c implementation in the preempt-rt tree.
 11  * Portions of said code are
 12  *
 13  *  Copyright (C) 2004  LynuxWorks, Inc., Igor Manyilov, Bill Huey
 14  *  Copyright (C) 2006  Esben Nielsen
 15  *  Copyright (C) 2006  Kihon Technologies Inc.,
 16  *                      Steven Rostedt <rostedt@goodmis.org>
 17  *
 18  * See rt.c in preempt-rt for proper credits and further information
 19  */
 20 #include <linux/sched.h>
 21 #include <linux/sched/rt.h>
 22 #include <linux/sched/debug.h>
 23 #include <linux/delay.h>
 24 #include <linux/export.h>
 25 #include <linux/spinlock.h>
 26 #include <linux/kallsyms.h>
 27 #include <linux/syscalls.h>
 28 #include <linux/interrupt.h>
 29 #include <linux/rbtree.h>
 30 #include <linux/fs.h>
 31 #include <linux/debug_locks.h>
 32 
 33 #include "rtmutex_common.h"
 34 
 35 static void printk_task(struct task_struct *p)
 36 {
 37         if (p)
 38                 printk("%16s:%5d [%p, %3d]", p->comm, task_pid_nr(p), p, p->prio);
 39         else
 40                 printk("<none>");
 41 }
 42 
 43 static void printk_lock(struct rt_mutex *lock, int print_owner)
 44 {
 45         if (lock->name)
 46                 printk(" [%p] {%s}\n",
 47                         lock, lock->name);
 48         else
 49                 printk(" [%p] {%s:%d}\n",
 50                         lock, lock->file, lock->line);
 51 
 52         if (print_owner && rt_mutex_owner(lock)) {
 53                 printk(".. ->owner: %p\n", lock->owner);
 54                 printk(".. held by:  ");
 55                 printk_task(rt_mutex_owner(lock));
 56                 printk("\n");
 57         }
 58 }
 59 
 60 void rt_mutex_debug_task_free(struct task_struct *task)
 61 {
 62         DEBUG_LOCKS_WARN_ON(!RB_EMPTY_ROOT(&task->pi_waiters.rb_root));
 63         DEBUG_LOCKS_WARN_ON(task->pi_blocked_on);
 64 }
 65 
 66 /*
 67  * We fill out the fields in the waiter to store the information about
 68  * the deadlock. We print when we return. act_waiter can be NULL in
 69  * case of a remove waiter operation.
 70  */
 71 void debug_rt_mutex_deadlock(enum rtmutex_chainwalk chwalk,
 72                              struct rt_mutex_waiter *act_waiter,
 73                              struct rt_mutex *lock)
 74 {
 75         struct task_struct *task;
 76 
 77         if (!debug_locks || chwalk == RT_MUTEX_FULL_CHAINWALK || !act_waiter)
 78                 return;
 79 
 80         task = rt_mutex_owner(act_waiter->lock);
 81         if (task && task != current) {
 82                 act_waiter->deadlock_task_pid = get_pid(task_pid(task));
 83                 act_waiter->deadlock_lock = lock;
 84         }
 85 }
 86 
 87 void debug_rt_mutex_print_deadlock(struct rt_mutex_waiter *waiter)
 88 {
 89         struct task_struct *task;
 90 
 91         if (!waiter->deadlock_lock || !debug_locks)
 92                 return;
 93 
 94         rcu_read_lock();
 95         task = pid_task(waiter->deadlock_task_pid, PIDTYPE_PID);
 96         if (!task) {
 97                 rcu_read_unlock();
 98                 return;
 99         }
100 
101         if (!debug_locks_off()) {
102                 rcu_read_unlock();
103                 return;
104         }
105 
106         pr_warn("\n");
107         pr_warn("============================================\n");
108         pr_warn("WARNING: circular locking deadlock detected!\n");
109         pr_warn("%s\n", print_tainted());
110         pr_warn("--------------------------------------------\n");
111         printk("%s/%d is deadlocking current task %s/%d\n\n",
112                task->comm, task_pid_nr(task),
113                current->comm, task_pid_nr(current));
114 
115         printk("\n1) %s/%d is trying to acquire this lock:\n",
116                current->comm, task_pid_nr(current));
117         printk_lock(waiter->lock, 1);
118 
119         printk("\n2) %s/%d is blocked on this lock:\n",
120                 task->comm, task_pid_nr(task));
121         printk_lock(waiter->deadlock_lock, 1);
122 
123         debug_show_held_locks(current);
124         debug_show_held_locks(task);
125 
126         printk("\n%s/%d's [blocked] stackdump:\n\n",
127                 task->comm, task_pid_nr(task));
128         show_stack(task, NULL);
129         printk("\n%s/%d's [current] stackdump:\n\n",
130                 current->comm, task_pid_nr(current));
131         dump_stack();
132         debug_show_all_locks();
133         rcu_read_unlock();
134 
135         printk("[ turning off deadlock detection."
136                "Please report this trace. ]\n\n");
137 }
138 
139 void debug_rt_mutex_lock(struct rt_mutex *lock)
140 {
141 }
142 
143 void debug_rt_mutex_unlock(struct rt_mutex *lock)
144 {
145         DEBUG_LOCKS_WARN_ON(rt_mutex_owner(lock) != current);
146 }
147 
148 void
149 debug_rt_mutex_proxy_lock(struct rt_mutex *lock, struct task_struct *powner)
150 {
151 }
152 
153 void debug_rt_mutex_proxy_unlock(struct rt_mutex *lock)
154 {
155         DEBUG_LOCKS_WARN_ON(!rt_mutex_owner(lock));
156 }
157 
158 void debug_rt_mutex_init_waiter(struct rt_mutex_waiter *waiter)
159 {
160         memset(waiter, 0x11, sizeof(*waiter));
161         waiter->deadlock_task_pid = NULL;
162 }
163 
164 void debug_rt_mutex_free_waiter(struct rt_mutex_waiter *waiter)
165 {
166         put_pid(waiter->deadlock_task_pid);
167         memset(waiter, 0x22, sizeof(*waiter));
168 }
169 
170 void debug_rt_mutex_init(struct rt_mutex *lock, const char *name, struct lock_class_key *key)
171 {
172         /*
173          * Make sure we are not reinitializing a held lock:
174          */
175         debug_check_no_locks_freed((void *)lock, sizeof(*lock));
176         lock->name = name;
177 
178 #ifdef CONFIG_DEBUG_LOCK_ALLOC
179         lockdep_init_map(&lock->dep_map, name, key, 0);
180 #endif
181 }
182 
183 

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