[PATCH] mutex subsystem, debugging code
[linux-2.6.git] / kernel / mutex-debug.c
1 /*
2  * kernel/mutex-debug.c
3  *
4  * Debugging code for mutexes
5  *
6  * Started by Ingo Molnar:
7  *
8  *  Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9  *
10  * lock debugging, locking tree, deadlock detection started by:
11  *
12  *  Copyright (C) 2004, LynuxWorks, Inc., Igor Manyilov, Bill Huey
13  *  Released under the General Public License (GPL).
14  */
15 #include <linux/mutex.h>
16 #include <linux/sched.h>
17 #include <linux/delay.h>
18 #include <linux/module.h>
19 #include <linux/spinlock.h>
20 #include <linux/kallsyms.h>
21 #include <linux/interrupt.h>
22
23 #include <asm/mutex.h>
24
25 #include "mutex-debug.h"
26
27 /*
28  * We need a global lock when we walk through the multi-process
29  * lock tree. Only used in the deadlock-debugging case.
30  */
31 DEFINE_SPINLOCK(debug_mutex_lock);
32
33 /*
34  * All locks held by all tasks, in a single global list:
35  */
36 LIST_HEAD(debug_mutex_held_locks);
37
38 /*
39  * In the debug case we carry the caller's instruction pointer into
40  * other functions, but we dont want the function argument overhead
41  * in the nondebug case - hence these macros:
42  */
43 #define __IP_DECL__             , unsigned long ip
44 #define __IP__                  , ip
45 #define __RET_IP__              , (unsigned long)__builtin_return_address(0)
46
47 /*
48  * "mutex debugging enabled" flag. We turn it off when we detect
49  * the first problem because we dont want to recurse back
50  * into the tracing code when doing error printk or
51  * executing a BUG():
52  */
53 int debug_mutex_on = 1;
54
55 static void printk_task(struct task_struct *p)
56 {
57         if (p)
58                 printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
59         else
60                 printk("<none>");
61 }
62
63 static void printk_ti(struct thread_info *ti)
64 {
65         if (ti)
66                 printk_task(ti->task);
67         else
68                 printk("<none>");
69 }
70
71 static void printk_task_short(struct task_struct *p)
72 {
73         if (p)
74                 printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
75         else
76                 printk("<none>");
77 }
78
79 static void printk_lock(struct mutex *lock, int print_owner)
80 {
81         printk(" [%p] {%s}\n", lock, lock->name);
82
83         if (print_owner && lock->owner) {
84                 printk(".. held by:  ");
85                 printk_ti(lock->owner);
86                 printk("\n");
87         }
88         if (lock->owner) {
89                 printk("... acquired at:               ");
90                 print_symbol("%s\n", lock->acquire_ip);
91         }
92 }
93
94 /*
95  * printk locks held by a task:
96  */
97 static void show_task_locks(struct task_struct *p)
98 {
99         switch (p->state) {
100         case TASK_RUNNING:              printk("R"); break;
101         case TASK_INTERRUPTIBLE:        printk("S"); break;
102         case TASK_UNINTERRUPTIBLE:      printk("D"); break;
103         case TASK_STOPPED:              printk("T"); break;
104         case EXIT_ZOMBIE:               printk("Z"); break;
105         case EXIT_DEAD:                 printk("X"); break;
106         default:                        printk("?"); break;
107         }
108         printk_task(p);
109         if (p->blocked_on) {
110                 struct mutex *lock = p->blocked_on->lock;
111
112                 printk(" blocked on mutex:");
113                 printk_lock(lock, 1);
114         } else
115                 printk(" (not blocked on mutex)\n");
116 }
117
118 /*
119  * printk all locks held in the system (if filter == NULL),
120  * or all locks belonging to a single task (if filter != NULL):
121  */
122 void show_held_locks(struct task_struct *filter)
123 {
124         struct list_head *curr, *cursor = NULL;
125         struct mutex *lock;
126         struct thread_info *t;
127         unsigned long flags;
128         int count = 0;
129
130         if (filter) {
131                 printk("------------------------------\n");
132                 printk("| showing all locks held by: |  (");
133                 printk_task_short(filter);
134                 printk("):\n");
135                 printk("------------------------------\n");
136         } else {
137                 printk("---------------------------\n");
138                 printk("| showing all locks held: |\n");
139                 printk("---------------------------\n");
140         }
141
142         /*
143          * Play safe and acquire the global trace lock. We
144          * cannot printk with that lock held so we iterate
145          * very carefully:
146          */
147 next:
148         debug_spin_lock_save(&debug_mutex_lock, flags);
149         list_for_each(curr, &debug_mutex_held_locks) {
150                 if (cursor && curr != cursor)
151                         continue;
152                 lock = list_entry(curr, struct mutex, held_list);
153                 t = lock->owner;
154                 if (filter && (t != filter->thread_info))
155                         continue;
156                 count++;
157                 cursor = curr->next;
158                 debug_spin_lock_restore(&debug_mutex_lock, flags);
159
160                 printk("\n#%03d:            ", count);
161                 printk_lock(lock, filter ? 0 : 1);
162                 goto next;
163         }
164         debug_spin_lock_restore(&debug_mutex_lock, flags);
165         printk("\n");
166 }
167
168 void mutex_debug_show_all_locks(void)
169 {
170         struct task_struct *g, *p;
171         int count = 10;
172         int unlock = 1;
173
174         printk("\nShowing all blocking locks in the system:\n");
175
176         /*
177          * Here we try to get the tasklist_lock as hard as possible,
178          * if not successful after 2 seconds we ignore it (but keep
179          * trying). This is to enable a debug printout even if a
180          * tasklist_lock-holding task deadlocks or crashes.
181          */
182 retry:
183         if (!read_trylock(&tasklist_lock)) {
184                 if (count == 10)
185                         printk("hm, tasklist_lock locked, retrying... ");
186                 if (count) {
187                         count--;
188                         printk(" #%d", 10-count);
189                         mdelay(200);
190                         goto retry;
191                 }
192                 printk(" ignoring it.\n");
193                 unlock = 0;
194         }
195         if (count != 10)
196                 printk(" locked it.\n");
197
198         do_each_thread(g, p) {
199                 show_task_locks(p);
200                 if (!unlock)
201                         if (read_trylock(&tasklist_lock))
202                                 unlock = 1;
203         } while_each_thread(g, p);
204
205         printk("\n");
206         show_held_locks(NULL);
207         printk("=============================================\n\n");
208
209         if (unlock)
210                 read_unlock(&tasklist_lock);
211 }
212
213 static void report_deadlock(struct task_struct *task, struct mutex *lock,
214                             struct mutex *lockblk, unsigned long ip)
215 {
216         printk("\n%s/%d is trying to acquire this lock:\n",
217                 current->comm, current->pid);
218         printk_lock(lock, 1);
219         printk("... trying at:                 ");
220         print_symbol("%s\n", ip);
221         show_held_locks(current);
222
223         if (lockblk) {
224                 printk("but %s/%d is deadlocking current task %s/%d!\n\n",
225                         task->comm, task->pid, current->comm, current->pid);
226                 printk("\n%s/%d is blocked on this lock:\n",
227                         task->comm, task->pid);
228                 printk_lock(lockblk, 1);
229
230                 show_held_locks(task);
231
232                 printk("\n%s/%d's [blocked] stackdump:\n\n",
233                         task->comm, task->pid);
234                 show_stack(task, NULL);
235         }
236
237         printk("\n%s/%d's [current] stackdump:\n\n",
238                 current->comm, current->pid);
239         dump_stack();
240         mutex_debug_show_all_locks();
241         printk("[ turning off deadlock detection. Please report this. ]\n\n");
242         local_irq_disable();
243 }
244
245 /*
246  * Recursively check for mutex deadlocks:
247  */
248 static int check_deadlock(struct mutex *lock, int depth,
249                           struct thread_info *ti, unsigned long ip)
250 {
251         struct mutex *lockblk;
252         struct task_struct *task;
253
254         if (!debug_mutex_on)
255                 return 0;
256
257         ti = lock->owner;
258         if (!ti)
259                 return 0;
260
261         task = ti->task;
262         lockblk = NULL;
263         if (task->blocked_on)
264                 lockblk = task->blocked_on->lock;
265
266         /* Self-deadlock: */
267         if (current == task) {
268                 DEBUG_OFF();
269                 if (depth)
270                         return 1;
271                 printk("\n==========================================\n");
272                 printk(  "[ BUG: lock recursion deadlock detected! |\n");
273                 printk(  "------------------------------------------\n");
274                 report_deadlock(task, lock, NULL, ip);
275                 return 0;
276         }
277
278         /* Ugh, something corrupted the lock data structure? */
279         if (depth > 20) {
280                 DEBUG_OFF();
281                 printk("\n===========================================\n");
282                 printk(  "[ BUG: infinite lock dependency detected!? |\n");
283                 printk(  "-------------------------------------------\n");
284                 report_deadlock(task, lock, lockblk, ip);
285                 return 0;
286         }
287
288         /* Recursively check for dependencies: */
289         if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) {
290                 printk("\n============================================\n");
291                 printk(  "[ BUG: circular locking deadlock detected! ]\n");
292                 printk(  "--------------------------------------------\n");
293                 report_deadlock(task, lock, lockblk, ip);
294                 return 0;
295         }
296         return 0;
297 }
298
299 /*
300  * Called when a task exits, this function checks whether the
301  * task is holding any locks, and reports the first one if so:
302  */
303 void mutex_debug_check_no_locks_held(struct task_struct *task)
304 {
305         struct list_head *curr, *next;
306         struct thread_info *t;
307         unsigned long flags;
308         struct mutex *lock;
309
310         if (!debug_mutex_on)
311                 return;
312
313         debug_spin_lock_save(&debug_mutex_lock, flags);
314         list_for_each_safe(curr, next, &debug_mutex_held_locks) {
315                 lock = list_entry(curr, struct mutex, held_list);
316                 t = lock->owner;
317                 if (t != task->thread_info)
318                         continue;
319                 list_del_init(curr);
320                 DEBUG_OFF();
321                 debug_spin_lock_restore(&debug_mutex_lock, flags);
322
323                 printk("BUG: %s/%d, lock held at task exit time!\n",
324                         task->comm, task->pid);
325                 printk_lock(lock, 1);
326                 if (lock->owner != task->thread_info)
327                         printk("exiting task is not even the owner??\n");
328                 return;
329         }
330         debug_spin_lock_restore(&debug_mutex_lock, flags);
331 }
332
333 /*
334  * Called when kernel memory is freed (or unmapped), or if a mutex
335  * is destroyed or reinitialized - this code checks whether there is
336  * any held lock in the memory range of <from> to <to>:
337  */
338 void mutex_debug_check_no_locks_freed(const void *from, const void *to)
339 {
340         struct list_head *curr, *next;
341         unsigned long flags;
342         struct mutex *lock;
343         void *lock_addr;
344
345         if (!debug_mutex_on)
346                 return;
347
348         debug_spin_lock_save(&debug_mutex_lock, flags);
349         list_for_each_safe(curr, next, &debug_mutex_held_locks) {
350                 lock = list_entry(curr, struct mutex, held_list);
351                 lock_addr = lock;
352                 if (lock_addr < from || lock_addr >= to)
353                         continue;
354                 list_del_init(curr);
355                 DEBUG_OFF();
356                 debug_spin_lock_restore(&debug_mutex_lock, flags);
357
358                 printk("BUG: %s/%d, active lock [%p(%p-%p)] freed!\n",
359                         current->comm, current->pid, lock, from, to);
360                 dump_stack();
361                 printk_lock(lock, 1);
362                 if (lock->owner != current_thread_info())
363                         printk("freeing task is not even the owner??\n");
364                 return;
365         }
366         debug_spin_lock_restore(&debug_mutex_lock, flags);
367 }
368
369 /*
370  * Must be called with lock->wait_lock held.
371  */
372 void debug_mutex_set_owner(struct mutex *lock,
373                            struct thread_info *new_owner __IP_DECL__)
374 {
375         lock->owner = new_owner;
376         DEBUG_WARN_ON(!list_empty(&lock->held_list));
377         if (debug_mutex_on) {
378                 list_add_tail(&lock->held_list, &debug_mutex_held_locks);
379                 lock->acquire_ip = ip;
380         }
381 }
382
383 void debug_mutex_init_waiter(struct mutex_waiter *waiter)
384 {
385         memset(waiter, 0x11, sizeof(*waiter));
386         waiter->magic = waiter;
387         INIT_LIST_HEAD(&waiter->list);
388 }
389
390 void debug_mutex_wake_waiter(struct mutex *lock, struct mutex_waiter *waiter)
391 {
392         SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock));
393         DEBUG_WARN_ON(list_empty(&lock->wait_list));
394         DEBUG_WARN_ON(waiter->magic != waiter);
395         DEBUG_WARN_ON(list_empty(&waiter->list));
396 }
397
398 void debug_mutex_free_waiter(struct mutex_waiter *waiter)
399 {
400         DEBUG_WARN_ON(!list_empty(&waiter->list));
401         memset(waiter, 0x22, sizeof(*waiter));
402 }
403
404 void debug_mutex_add_waiter(struct mutex *lock, struct mutex_waiter *waiter,
405                             struct thread_info *ti __IP_DECL__)
406 {
407         SMP_DEBUG_WARN_ON(!spin_is_locked(&lock->wait_lock));
408         check_deadlock(lock, 0, ti, ip);
409         /* Mark the current thread as blocked on the lock: */
410         ti->task->blocked_on = waiter;
411         waiter->lock = lock;
412 }
413
414 void mutex_remove_waiter(struct mutex *lock, struct mutex_waiter *waiter,
415                          struct thread_info *ti)
416 {
417         DEBUG_WARN_ON(list_empty(&waiter->list));
418         DEBUG_WARN_ON(waiter->task != ti->task);
419         DEBUG_WARN_ON(ti->task->blocked_on != waiter);
420         ti->task->blocked_on = NULL;
421
422         list_del_init(&waiter->list);
423         waiter->task = NULL;
424 }
425
426 void debug_mutex_unlock(struct mutex *lock)
427 {
428         DEBUG_WARN_ON(lock->magic != lock);
429         DEBUG_WARN_ON(!lock->wait_list.prev && !lock->wait_list.next);
430         DEBUG_WARN_ON(lock->owner != current_thread_info());
431         if (debug_mutex_on) {
432                 DEBUG_WARN_ON(list_empty(&lock->held_list));
433                 list_del_init(&lock->held_list);
434         }
435 }
436
437 void debug_mutex_init(struct mutex *lock, const char *name)
438 {
439         /*
440          * Make sure we are not reinitializing a held lock:
441          */
442         mutex_debug_check_no_locks_freed((void *)lock, (void *)(lock + 1));
443         lock->owner = NULL;
444         INIT_LIST_HEAD(&lock->held_list);
445         lock->name = name;
446         lock->magic = lock;
447 }
448
449 /***
450  * mutex_destroy - mark a mutex unusable
451  * @lock: the mutex to be destroyed
452  *
453  * This function marks the mutex uninitialized, and any subsequent
454  * use of the mutex is forbidden. The mutex must not be locked when
455  * this function is called.
456  */
457 void fastcall mutex_destroy(struct mutex *lock)
458 {
459         DEBUG_WARN_ON(mutex_is_locked(lock));
460         lock->magic = NULL;
461 }
462
463 EXPORT_SYMBOL_GPL(mutex_destroy);
464