aboutsummaryrefslogtreecommitdiff
path: root/kernel/mutex-debug.c
blob: fe0e9f2714d34fa6789d86e002e97d93cd8aa409 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
/*
 * kernel/mutex-debug.c
 *
 * Debugging code for mutexes
 *
 * Started by Ingo Molnar:
 *
 *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
 *
 * lock debugging, locking tree, deadlock detection started by:
 *
 *  Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
 *  Released under the General Public License (GPL).
 */
#include <linux/mutex.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/module.h>
#include <linux/poison.h>
#include <linux/spinlock.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>

#include "mutex-debug.h"

/*
 * We need a global lock when we walk through the multi-process
 * lock tree. Only used in the deadlock-debugging case.
 */
DEFINE_SPINLOCK(debug_mutex_lock);

/*
 * All locks held by all tasks, in a single global list:
 */
LIST_HEAD(debug_mutex_held_locks);

/*
 * In the debug case we carry the caller's instruction pointer into
 * other functions, but we dont want the function argument overhead
 * in the nondebug case - hence these macros:
 */
#define __IP_DECL__		, unsigned long ip
#define __IP__			, ip
#define __RET_IP__		, (unsigned long)__builtin_return_address(0)

/*
 * "mutex debugging enabled" flag. We turn it off when we detect
 * the first problem because we dont want to recurse back
 * into the tracing code when doing error printk or
 * executing a BUG():
 */
int debug_mutex_on = 1;

static void printk_task(struct task_struct *p)
{
	if (p)
		printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
	else
		printk("<none>");
}

static void printk_ti(struct thread_info *ti)
{
	if (ti)
		printk_task(ti->task);
	else
		printk("<none>");
}

static void printk_task_short(struct task_struct *p)
{
	if (p)
		printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
	else
		printk("<none>");
}

static void printk_lock(struct mutex *lock, int print_owner)
{
	printk(" [%p] {%s}\n", lock, lock->name);

	if (print_owner && lock->owner) {
		printk(".. held by:  ");
		printk_ti(lock->owner);
		printk("\n");
	}
	if (lock->owner) {
		printk("... acquired at:               ");
		print_symbol("%s\n", lock->acquire_ip);
	}
}

/*
 * printk locks held by a task:
 */
static void show_task_locks(struct task_struct *p)
{
	switch (p->state) {
	case TASK_RUNNING:		printk("R"); break;
	case TASK_INTERRUPTIBLE:	printk("S"); break;
	case TASK_UNINTERRUPTIBLE:	printk("D"); break;
	case TASK_STOPPED:		printk("T"); break;
	case EXIT_ZOMBIE:		printk("Z"); break;
	case EXIT_DEAD:			printk("X"); break;
	default:			printk("?"); break;
	}
	printk_task(p);
	if (p->blocked_on) {
		struct mutex *lock = p->blocked_on->lock;

		printk(" blocked on mutex:");
		printk_lock(lock, 1);
	} else
		printk(" (not blocked on mutex)\n");
}

/*
 * printk all locks held in the system (if filter == NULL),
 * or all locks belonging to a single task (if filter != NULL):
 */
void show_held_locks(struct task_struct *filter)
{
	struct list_head *curr, *cursor = NULL;
	struct mutex *lock;
	struct thread_info *t;
	unsigned long flags;
	int count = 0;

	if (filter) {
		printk("------------------------------\n");
		printk("| showing all locks held by: |  (");
		printk_task_short(filter);
		printk("):\n");
		printk("------------------------------\n");
	} else {
		printk("---------------------------\n");
		printk("| showing all locks held: |\n");
		printk("---------------------------\n");
	}

	/*
	 * Play safe and acquire the global trace lock. We
	 * cannot printk with that lock held so we iterate
	 * very carefully:
	 */
next:
	debug_spin_lock_save(&debug_mutex_lock, flags);
	list_for_each(curr, &debug_mutex_held_locks) {
		if (cursor && curr != cursor)
			continue;
		lock = list_entry(curr, struct mutex, held_list);
		t = lock->owner;
		if (filter && (t != filter->thread_info))
			continue;
		count++;
		cursor = curr->next;
		debug_spin_unlock_restore(&debug_mutex_lock, flags);

		printk("\n#%03d:            ", count);
		printk_lock(lock, filter ? 0 : 1);
		goto next;
	}
	debug_spin_unlock_restore(&debug_mutex_lock, flags);
	printk("\n");
}

void mutex_debug_show_all_locks(void)
{
	struct task_struct *g, *p;
	int count = 10;
	int unlock = 1;

	printk("\nShowing all blocking locks in the system:\n");

	/*
	 * Here we try to get the tasklist_lock as hard as possible,
	 * if not successful after 2 seconds we ignore it (but keep
	 * trying). This is to enable a debug printout even if a
	 * tasklist_lock-holding task deadlocks or crashes.
	 */
retry:
	if (!read_trylock(&tasklist_lock)) {
		if (count == 10)
			printk("hm, tasklist_lock locked, retrying... ");
		if (count) {
			count--;
			printk(" #%d", 10-count);
			mdelay(200);
			goto retry;
		}
		printk(" ignoring it.\n");
		unlock = 0;
	}
	if (count != 10)
		printk(" locked it.\n");

	do_each_thread(g, p) {
		show_task_locks(p);
		if (!unlock)
			if (read_trylock(&tasklist_lock))
				unlock = 1;
	} while_each_thread(g, p);

	printk("\n");
	show_held_locks(NULL);
	printk("=============================================\n\n");

	if (unlock)
		read_unlock(&tasklist_lock);
}

static void report_deadlock(struct task_struct *task, struct mutex *lock,
			    struct mutex *lockblk, unsigned long ip)
{
	printk("\n%s/%d is trying to acquire this lock:\n",
		current->comm, current->pid);
	printk_lock(lock, 1);
	printk("... trying at:                 ");
	print_symbol("%s\n", ip);
	show_held_locks(current);

	if (lockblk) {
		printk("but %s/%d is deadlocking current task %s/%d!\n\n",
			task->comm, task->pid, current->comm, current->pid);
		printk("\n%s/%d is blocked on this lock:\n",
			task->comm, task->pid);
		printk_lock(lockblk, 1);

		show_held_locks(task);

		printk("\n%s/%d's [blocked] stackdump:\n\n",
			task->comm, task->pid);
		show_stack(task, NULL);
	}

	printk("\n%s/%d's [current] stackdump:\n\n",
		current->comm, current->pid);
	dump_stack();
	mutex_debug_show_all_locks();
	printk("[ turning off deadlock detection. Please report this. ]\n\n");
	local_irq_disable();
}

/*
 * Recursively check for mutex deadlocks:
 */
static int check_deadlock(struct mutex *lock, int depth,
			  struct thread_info *ti, unsigned long ip)
{
	struct mutex *lockblk;
	struct task_struct *task;

	if (!debug_mutex_on)
		return 0;

	ti = lock->owner;
	if (!ti)
		return 0;

	task = ti->task;
	lockblk = NULL;
	if (task->blocked_on)
		lockblk = task->blocked_on->lock;

	/* Self-deadlock: */
	if (current == task) {
		DEBUG_OFF();
		if (depth)
			return 1;
		printk("\n==========================================\n");
		printk(  "[ BUG: lock recursion deadlock detected! |\n");
		printk(  "------------------------------------------\n");
		report_deadlock(task, lock, NULL, ip);
		return 0;
	}

	/* Ugh, something corrupted the lock data structure? */
	if (depth > 20) {
		DEBUG_OFF();
		printk("\n===========================================\n");
		printk(  "[ BUG: infinite lock dependency detected!? |\n");
		printk(  "-------------------------------------------\n");
		report_deadlock(task, lock, lockblk, ip);
		return 0;
	}

	/* Recursively check for dependencies: */
	if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) {
		printk("\n============================================\n");
		printk(  "[ BUG: circular locking deadlock detected! ]\n");
		printk(  "--------------------------------------------\n");
		report_deadlock(task, lock, lockblk, ip);
		return 0;
	}
	return 0;
}

/*
 * Called when a task exits, this function checks whether the
 * task is holding any locks, and reports the first one if so:
 */
void mutex_debug_check_no_locks_held(struct task_struct *task)
{
	struct list_head *curr, *next;
	struct thread_info *t;
	unsigned long flags;
	struct mutex *lock;

	if (!debug_mutex_on)
		return;

	debug_spin_lock_save(&debug_mutex_lock, flags);
	list_for_each_safe(curr, next, &debug_mutex_held_locks) {
		lock = list_entry(curr, struct mutex, held_list);
		t = lock->owner;
		if (t != task->thread_info)
			continue;
		list_del_init(curr);
		DEBUG_OFF();
		debug_spin_unlock_restore(&debug_mutex_lock, flags);

		printk("BUG: %s/%d, lock held at task exit time!\n",
			task->comm, task->pid);
		printk_lock(lock, 1);
		if (lock->owner != task->thread_info)
			printk("exiting task is not even the owner??\n");
		return;
	}
	debug_spin_unlock_restore(&debug_mutex_lock, flags);
}

/*
 * Called when kernel memory is freed (or unmapped), or if a mutex
 * is destroyed or reinitialized - this code checks whether there is
 * any held lock in the memory range of <from> to <to>:
 */
void mutex_debug_check_no_locks_freed(const void *from, unsigned long len)
{
	struct list_head *curr, *next;
	const void *to = from + len;
	unsigned long flags;
	struct mutex *lock;
	void *lock_addr;

	if (!debug_mutex_on)
		return;

	debug_spin_lock_save(&debug_mutex_lock, flags);
	list_for_each_safe(curr, next, &debug_mutex_held_locks) {
		lock = list_entry(curr, struct mutex, held_list);
		lock_addr = lock;
		if (lock_addr < from || lock_addr >= to)
			continue;
		list_del_init(curr);
		DEBUG_OFF();
		debug_spin_unlock_restore(&debug_mutex_lock, flags);

		printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n",
			current->comm, current->pid, lock, from, to);
		dump_stack();
		printk_lock(lock, 1);
		if (lock->owner != current_thread_info())
			printk("freeing task is not even the owner??\n");
		return;
	}
	debug_spin_unlock_restore(&debug_mutex_lock, flags);
}

/*
 * Must be called with lock->wait_lock held.
 */
void debug_mutex_set_owner(struct mutex *lock,
			   struct thread_info *new_owner __IP_DECL__)
{
	lock->owner = new_owner;
	DEBUG_LOCKS_WARN_ON(!list_empty(&lock->held_list));
	if (debug_mutex_on) {
		list_add_tail(&lock->held_list, &debug_mutex_held_locks);
		lock->acquire_ip = ip;
	}
}

void debug_mutex_init_waiter(struct mutex_waiter *waiter)
{
	memset(waiter, MUTEX_DEBUG_INIT, sizeof(*waiter));
	waiter->magic = waiter;
	INIT_LIST_HEAD(&waiter->list);
}

void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter)
{
	SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
	DEBUG_LOCKS_WARN_ON(list_empty(&lock->wait_list));
	DEBUG_LOCKS_WARN_ON(waiter->magic != waiter);
	DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
}

void debug_mutex_free_waiter(struct mutex_waiter *waiter)
{
	DEBUG_LOCKS_WARN_ON(!list_empty(&waiter->list));
	memset(waiter, MUTEX_DEBUG_FREE, sizeof(*waiter));
}

void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
			    struct thread_info *ti __IP_DECL__)
{
	SMP_DEBUG_LOCKS_WARN_ON(!spin_is_locked(&lock->wait_lock));
	check_deadlock(lock, 0, ti, ip);
	/* Mark the current thread as blocked on the lock: */
	ti->task->blocked_on = waiter;
	waiter->lock = lock;
}

void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
			 struct thread_info *ti)
{
	DEBUG_LOCKS_WARN_ON(list_empty(&waiter->list));
	DEBUG_LOCKS_WARN_ON(waiter->task != ti->task);
	DEBUG_LOCKS_WARN_ON(ti->task->blocked_on != waiter);
	ti->task->blocked_on = NULL;

	list_del_init(&waiter->list);
	waiter->task = NULL;
}

void debug_mutex_unlock(struct mutex *lock)
{
	DEBUG_LOCKS_WARN_ON(lock->magic != lock);
	DEBUG_LOCKS_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
	DEBUG_LOCKS_WARN_ON(lock->owner != current_thread_info());
	if (debug_mutex_on) {
		DEBUG_LOCKS_WARN_ON(list_empty(&lock->held_list));
		list_del_init(&lock->held_list);
	}
}

void debug_mutex_init(struct mutex *lock, const char *name)
{
	/*
	 * Make sure we are not reinitializing a held lock:
	 */
	mutex_debug_check_no_locks_freed((void *)lock, sizeof(*lock));
	lock->owner = NULL;
	INIT_LIST_HEAD(&lock->held_list);
	lock->name = name;
	lock->magic = lock;
}

/***
 * mutex_destroy - mark a mutex unusable
 * @lock: the mutex to be destroyed
 *
 * This function marks the mutex uninitialized, and any subsequent
 * use of the mutex is forbidden. The mutex must not be locked when
 * this function is called.
 */
void fastcall mutex_destroy(struct mutex *lock)
{
	DEBUG_LOCKS_WARN_ON(mutex_is_locked(lock));
	lock->magic = NULL;
}

EXPORT_SYMBOL_GPL(mutex_destroy);