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/poison.h>
  20 #include <linux/spinlock.h>
  21 #include <linux/kallsyms.h>
  22 #include <linux/interrupt.h>
  23
  24 #include "mutex-debug.h"
  25
  26 /*
  27  * We need a global lock when we walk through the multi-process
  28  * lock tree. Only used in the deadlock-debugging case.
  29  */
  30 DEFINE_SPINLOCK(debug_mutex_lock);
  31
  32 /*
  33  * All locks held by all tasks, in a single global list:
  34  */
  35 LIST_HEAD(debug_mutex_held_locks);
  36
  37 /*
  38  * In the debug case we carry the caller's instruction pointer into
  39  * other functions, but we dont want the function argument overhead
  40  * in the nondebug case - hence these macros:
  41  */
  42 #define __IP_DECL__             , unsigned long ip
  43 #define __IP__                  , ip
  44 #define __RET_IP__              , (unsigned long)__builtin_return_address(0)
  45
  46 /*
  47  * "mutex debugging enabled" flag. We turn it off when we detect
  48  * the first problem because we dont want to recurse back
  49  * into the tracing code when doing error printk or
  50  * executing a BUG():
  51  */
  52 int debug_mutex_on = 1;
  53
  54 static void printk_task(struct task_struct *p)
  55 {
  56         if (p)
  57                 printk("%16s:%5d [%p, %3d]", p->comm, p->pid, p, p->prio);
  58         else
  59                 printk("<none>");
  60 }
  61
  62 static void printk_ti(struct thread_info *ti)
  63 {
  64         if (ti)
  65                 printk_task(ti->task);
  66         else
  67                 printk("<none>");
  68 }
  69
  70 static void printk_task_short(struct task_struct *p)
  71 {
  72         if (p)
  73                 printk("%s/%d [%p, %3d]", p->comm, p->pid, p, p->prio);
  74         else
  75                 printk("<none>");
  76 }
  77
  78 static void printk_lock(struct mutex *lock, int print_owner)
  79 {
  80         printk(" [%p] {%s}\n", lock, lock->name);
  81
  82         if (print_owner && lock->owner) {
  83                 printk(".. held by:  ");
  84                 printk_ti(lock->owner);
  85                 printk("\n");
  86         }
  87         if (lock->owner) {
  88                 printk("... acquired at:               ");
  89                 print_symbol("%s\n", lock->acquire_ip);
  90         }
  91 }
  92
  93 /*
  94  * printk locks held by a task:
  95  */
  96 static void show_task_locks(struct task_struct *p)
  97 {
  98         switch (p->state) {
  99         case TASK_RUNNING:              printk("R"); break;
 100         case TASK_INTERRUPTIBLE:        printk("S"); break;
 101         case TASK_UNINTERRUPTIBLE:      printk("D"); break;
 102         case TASK_STOPPED:              printk("T"); break;
 103         case EXIT_ZOMBIE:               printk("Z"); break;
 104         case EXIT_DEAD:                 printk("X"); break;
 105         default:                        printk("?"); break;
 106         }
 107         printk_task(p);
 108         if (p->blocked_on) {
 109                 struct mutex *lock = p->blocked_on->lock;
 110
 111                 printk(" blocked on mutex:");
 112                 printk_lock(lock, 1);
 113         } else
 114                 printk(" (not blocked on mutex)\n");
 115 }
 116
 117 /*
 118  * printk all locks held in the system (if filter == NULL),
 119  * or all locks belonging to a single task (if filter != NULL):
 120  */
 121 void show_held_locks(struct task_struct *filter)
 122 {
 123         struct list_head *curr, *cursor = NULL;
 124         struct mutex *lock;
 125         struct thread_info *t;
 126         unsigned long flags;
 127         int count = 0;
 128
 129         if (filter) {
 130                 printk("------------------------------\n");
 131                 printk("| showing all locks held by: |  (");
 132                 printk_task_short(filter);
 133                 printk("):\n");
 134                 printk("------------------------------\n");
 135         } else {
 136                 printk("---------------------------\n");
 137                 printk("| showing all locks held: |\n");
 138                 printk("---------------------------\n");
 139         }
 140
 141         /*
 142          * Play safe and acquire the global trace lock. We
 143          * cannot printk with that lock held so we iterate
 144          * very carefully:
 145          */
 146 next:
 147         debug_spin_lock_save(&debug_mutex_lock, flags);
 148         list_for_each(curr, &debug_mutex_held_locks) {
 149                 if (cursor && curr != cursor)
 150                         continue;
 151                 lock = list_entry(curr, struct mutex, held_list);
 152                 t = lock->owner;
 153                 if (filter && (t != filter->thread_info))
 154                         continue;
 155                 count++;
 156                 cursor = curr->next;
 157                 debug_spin_unlock_restore(&debug_mutex_lock, flags);
 158
 159                 printk("\n#%03d:            ", count);
 160                 printk_lock(lock, filter ? 0 : 1);
 161                 goto next;
 162         }
 163         debug_spin_unlock_restore(&debug_mutex_lock, flags);
 164         printk("\n");
 165 }
 166
 167 void mutex_debug_show_all_locks(void)
 168 {
 169         struct task_struct *g, *p;
 170         int count = 10;
 171         int unlock = 1;
 172
 173         printk("\nShowing all blocking locks in the system:\n");
 174
 175         /*
 176          * Here we try to get the tasklist_lock as hard as possible,
 177          * if not successful after 2 seconds we ignore it (but keep
 178          * trying). This is to enable a debug printout even if a
 179          * tasklist_lock-holding task deadlocks or crashes.
 180          */
 181 retry:
 182         if (!read_trylock(&tasklist_lock)) {
 183                 if (count == 10)
 184                         printk("hm, tasklist_lock locked, retrying... ");
 185                 if (count) {
 186                         count--;
 187                         printk(" #%d", 10-count);
 188                         mdelay(200);
 189                         goto retry;
 190                 }
 191                 printk(" ignoring it.\n");
 192                 unlock = 0;
 193         }
 194         if (count != 10)
 195                 printk(" locked it.\n");
 196
 197         do_each_thread(g, p) {
 198                 show_task_locks(p);
 199                 if (!unlock)
 200                         if (read_trylock(&tasklist_lock))
 201                                 unlock = 1;
 202         } while_each_thread(g, p);
 203
 204         printk("\n");
 205         show_held_locks(NULL);
 206         printk("=============================================\n\n");
 207
 208         if (unlock)
 209                 read_unlock(&tasklist_lock);
 210 }
 211
 212 static void report_deadlock(struct task_struct *task, struct mutex *lock,
 213                             struct mutex *lockblk, unsigned long ip)
 214 {
 215         printk("\n%s/%d is trying to acquire this lock:\n",
 216                 current->comm, current->pid);
 217         printk_lock(lock, 1);
 218         printk("... trying at:                 ");
 219         print_symbol("%s\n", ip);
 220         show_held_locks(current);
 221
 222         if (lockblk) {
 223                 printk("but %s/%d is deadlocking current task %s/%d!\n\n",
 224                         task->comm, task->pid, current->comm, current->pid);
 225                 printk("\n%s/%d is blocked on this lock:\n",
 226                         task->comm, task->pid);
 227                 printk_lock(lockblk, 1);
 228
 229                 show_held_locks(task);
 230
 231                 printk("\n%s/%d's [blocked] stackdump:\n\n",
 232                         task->comm, task->pid);
 233                 show_stack(task, NULL);
 234         }
 235
 236         printk("\n%s/%d's [current] stackdump:\n\n",
 237                 current->comm, current->pid);
 238         dump_stack();
 239         mutex_debug_show_all_locks();
 240         printk("[ turning off deadlock detection. Please report this. ]\n\n");
 241         local_irq_disable();
 242 }
 243
 244 /*
 245  * Recursively check for mutex deadlocks:
 246  */
 247 static int check_deadlock(struct mutex *lock, int depth,
 248                           struct thread_info *ti, unsigned long ip)
 249 {
 250         struct mutex *lockblk;
 251         struct task_struct *task;
 252
 253         if (!debug_mutex_on)
 254                 return 0;
 255
 256         ti = lock->owner;
 257         if (!ti)
 258                 return 0;
 259
 260         task = ti->task;
 261         lockblk = NULL;
 262         if (task->blocked_on)
 263                 lockblk = task->blocked_on->lock;
 264
 265         /* Self-deadlock: */
 266         if (current == task) {
 267                 DEBUG_OFF();
 268                 if (depth)
 269                         return 1;
 270                 printk("\n==========================================\n");
 271                 printk(  "[ BUG: lock recursion deadlock detected! |\n");
 272                 printk(  "------------------------------------------\n");
 273                 report_deadlock(task, lock, NULL, ip);
 274                 return 0;
 275         }
 276
 277         /* Ugh, something corrupted the lock data structure? */
 278         if (depth > 20) {
 279                 DEBUG_OFF();
 280                 printk("\n===========================================\n");
 281                 printk(  "[ BUG: infinite lock dependency detected!? |\n");
 282                 printk(  "-------------------------------------------\n");
 283                 report_deadlock(task, lock, lockblk, ip);
 284                 return 0;
 285         }
 286
 287         /* Recursively check for dependencies: */
 288         if (lockblk && check_deadlock(lockblk, depth+1, ti, ip)) {
 289                 printk("\n============================================\n");
 290                 printk(  "[ BUG: circular locking deadlock detected! ]\n");
 291                 printk(  "--------------------------------------------\n");
 292                 report_deadlock(task, lock, lockblk, ip);
 293                 return 0;
 294         }
 295         return 0;
 296 }
 297
 298 /*
 299  * Called when a task exits, this function checks whether the
 300  * task is holding any locks, and reports the first one if so:
 301  */
 302 void mutex_debug_check_no_locks_held(struct task_struct *task)
 303 {
 304         struct list_head *curr, *next;
 305         struct thread_info *t;
 306         unsigned long flags;
 307         struct mutex *lock;
 308
 309         if (!debug_mutex_on)
 310                 return;
 311
 312         debug_spin_lock_save(&debug_mutex_lock, flags);
 313         list_for_each_safe(curr, next, &debug_mutex_held_locks) {
 314                 lock = list_entry(curr, struct mutex, held_list);
 315                 t = lock->owner;
 316                 if (t != task->thread_info)
 317                         continue;
 318                 list_del_init(curr);
 319                 DEBUG_OFF();
 320                 debug_spin_unlock_restore(&debug_mutex_lock, flags);
 321
 322                 printk("BUG: %s/%d, lock held at task exit time!\n",
 323                         task->comm, task->pid);
 324                 printk_lock(lock, 1);
 325                 if (lock->owner != task->thread_info)
 326                         printk("exiting task is not even the owner??\n");
 327                 return;
 328         }
 329         debug_spin_unlock_restore(&debug_mutex_lock, flags);
 330 }
 331
 332 /*
 333  * Called when kernel memory is freed (or unmapped), or if a mutex
 334  * is destroyed or reinitialized - this code checks whether there is
 335  * any held lock in the memory range of <from> to <to>:
 336  */
 337 void mutex_debug_check_no_locks_freed(const void *from, unsigned long len)
 338 {
 339         struct list_head *curr, *next;
 340         const void *to = from + len;
 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_unlock_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_unlock_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, MUTEX_DEBUG_INIT, 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, MUTEX_DEBUG_FREE, 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, sizeof(*lock));
 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);