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