nptl/pthread_mutex_lock.c

   1 /* Copyright (C) 2002-2007, 2008 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <stdlib.h>
  23 #include <unistd.h>
  24 #include <not-cancel.h>
  25 #include "pthreadP.h"
  26 #include <lowlevellock.h>
  27
  28
  29 #ifndef LLL_MUTEX_LOCK
  30 # define LLL_MUTEX_LOCK(mutex) \
  31   lll_lock ((mutex)->__data.__lock, PTHREAD_MUTEX_PSHARED (mutex))
  32 # define LLL_MUTEX_TRYLOCK(mutex) \
  33   lll_trylock ((mutex)->__data.__lock)
  34 # define LLL_ROBUST_MUTEX_LOCK(mutex, id) \
  35   lll_robust_lock ((mutex)->__data.__lock, id, \
  36                    PTHREAD_ROBUST_MUTEX_PSHARED (mutex))
  37 #endif
  38
  39
  40 static int __pthread_mutex_lock_full (pthread_mutex_t *mutex)
  41      __attribute_noinline__;
  42
  43
  44 int
  45 __pthread_mutex_lock (mutex)
  46      pthread_mutex_t *mutex;
  47 {
  48   assert (sizeof (mutex->__size) >= sizeof (mutex->__data));
  49
  50   unsigned int type = PTHREAD_MUTEX_TYPE (mutex);
  51   if (__builtin_expect (type & ~PTHREAD_MUTEX_KIND_MASK_NP, 0))
  52     return __pthread_mutex_lock_full (mutex);
  53
  54   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  55
  56   if (__builtin_expect (type, PTHREAD_MUTEX_TIMED_NP)
  57       == PTHREAD_MUTEX_TIMED_NP)
  58     {
  59     simple:
  60       /* Normal mutex.  */
  61       LLL_MUTEX_LOCK (mutex);
  62       assert (mutex->__data.__owner == 0);
  63     }
  64   else if (__builtin_expect (type == PTHREAD_MUTEX_RECURSIVE_NP, 1))
  65     {
  66       /* Recursive mutex.  */
  67
  68       /* Check whether we already hold the mutex.  */
  69       if (mutex->__data.__owner == id)
  70         {
  71           /* Just bump the counter.  */
  72           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  73             /* Overflow of the counter.  */
  74             return EAGAIN;
  75
  76           ++mutex->__data.__count;
  77
  78           return 0;
  79         }
  80
  81       /* We have to get the mutex.  */
  82       LLL_MUTEX_LOCK (mutex);
  83
  84       assert (mutex->__data.__owner == 0);
  85       mutex->__data.__count = 1;
  86     }
  87   else if (__builtin_expect (type == PTHREAD_MUTEX_ADAPTIVE_NP, 1))
  88     {
  89       if (! __is_smp)
  90         goto simple;
  91
  92       if (LLL_MUTEX_TRYLOCK (mutex) != 0)
  93         {
  94           int cnt = 0;
  95           int max_cnt = MIN (MAX_ADAPTIVE_COUNT,
  96                              mutex->__data.__spins * 2 + 10);
  97           do
  98             {
  99               if (cnt++ >= max_cnt)
 100                 {
 101                   LLL_MUTEX_LOCK (mutex);
 102                   break;
 103                 }
 104
 105 #ifdef BUSY_WAIT_NOP
 106               BUSY_WAIT_NOP;
 107 #endif
 108             }
 109           while (LLL_MUTEX_TRYLOCK (mutex) != 0);
 110
 111           mutex->__data.__spins += (cnt - mutex->__data.__spins) / 8;
 112         }
 113       assert (mutex->__data.__owner == 0);
 114     }
 115   else
 116     {
 117       assert (type == PTHREAD_MUTEX_ERRORCHECK_NP);
 118       /* Check whether we already hold the mutex.  */
 119       if (__builtin_expect (mutex->__data.__owner == id, 0))
 120         return EDEADLK;
 121       goto simple;
 122     }
 123
 124  out:
 125   /* Record the ownership.  */
 126   mutex->__data.__owner = id;
 127 #ifndef NO_INCR
 128   ++mutex->__data.__nusers;
 129 #endif
 130
 131   return 0;
 132 }
 133
 134 static int
 135 __pthread_mutex_lock_full (pthread_mutex_t *mutex)
 136 {
 137   int oldval;
 138   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
 139
 140   switch (PTHREAD_MUTEX_TYPE (mutex))
 141     {
 142     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
 143     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
 144     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
 145     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
 146       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 147                      &mutex->__data.__list.__next);
 148
 149       oldval = mutex->__data.__lock;
 150       do
 151         {
 152         again:
 153           if ((oldval & FUTEX_OWNER_DIED) != 0)
 154             {
 155               /* The previous owner died.  Try locking the mutex.  */
 156               int newval = id;
 157 #ifdef NO_INCR
 158               newval |= FUTEX_WAITERS;
 159 #else
 160               newval |= (oldval & FUTEX_WAITERS);
 161 #endif
 162
 163               newval
 164                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 165                                                        newval, oldval);
 166
 167               if (newval != oldval)
 168                 {
 169                   oldval = newval;
 170                   goto again;
 171                 }
 172
 173               /* We got the mutex.  */
 174               mutex->__data.__count = 1;
 175               /* But it is inconsistent unless marked otherwise.  */
 176               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 177
 178               ENQUEUE_MUTEX (mutex);
 179               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 180
 181               /* Note that we deliberately exit here.  If we fall
 182                  through to the end of the function __nusers would be
 183                  incremented which is not correct because the old
 184                  owner has to be discounted.  If we are not supposed
 185                  to increment __nusers we actually have to decrement
 186                  it here.  */
 187 #ifdef NO_INCR
 188               --mutex->__data.__nusers;
 189 #endif
 190
 191               return EOWNERDEAD;
 192             }
 193
 194           /* Check whether we already hold the mutex.  */
 195           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 196             {
 197               int kind = PTHREAD_MUTEX_TYPE (mutex);
 198               if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 199                 {
 200                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 201                                  NULL);
 202                   return EDEADLK;
 203                 }
 204
 205               if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 206                 {
 207                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 208                                  NULL);
 209
 210                   /* Just bump the counter.  */
 211                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 212                     /* Overflow of the counter.  */
 213                     return EAGAIN;
 214
 215                   ++mutex->__data.__count;
 216
 217                   return 0;
 218                 }
 219             }
 220
 221           oldval = LLL_ROBUST_MUTEX_LOCK (mutex, id);
 222
 223           if (__builtin_expect (mutex->__data.__owner
 224                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 225             {
 226               /* This mutex is now not recoverable.  */
 227               mutex->__data.__count = 0;
 228               lll_unlock (mutex->__data.__lock,
 229                           PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 230               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 231               return ENOTRECOVERABLE;
 232             }
 233         }
 234       while ((oldval & FUTEX_OWNER_DIED) != 0);
 235
 236       mutex->__data.__count = 1;
 237       ENQUEUE_MUTEX (mutex);
 238       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 239       break;
 240
 241     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 242     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 243     case PTHREAD_MUTEX_PI_NORMAL_NP:
 244     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 245     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 246     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 247     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 248     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 249       {
 250         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 251         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 252
 253         if (robust)
 254           /* Note: robust PI futexes are signaled by setting bit 0.  */
 255           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 256                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 257                                    | 1));
 258
 259         oldval = mutex->__data.__lock;
 260
 261         /* Check whether we already hold the mutex.  */
 262         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 263           {
 264             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 265               {
 266                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 267                 return EDEADLK;
 268               }
 269
 270             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 271               {
 272                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 273
 274                 /* Just bump the counter.  */
 275                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 276                   /* Overflow of the counter.  */
 277                   return EAGAIN;
 278
 279                 ++mutex->__data.__count;
 280
 281                 return 0;
 282               }
 283           }
 284
 285         int newval = id;
 286 #ifdef NO_INCR
 287         newval |= FUTEX_WAITERS;
 288 #endif
 289         oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 290                                                       newval, 0);
 291
 292         if (oldval != 0)
 293           {
 294             /* The mutex is locked.  The kernel will now take care of
 295                everything.  */
 296             int private = (robust
 297                            ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
 298                            : PTHREAD_MUTEX_PSHARED (mutex));
 299             INTERNAL_SYSCALL_DECL (__err);
 300             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 301                                       __lll_private_flag (FUTEX_LOCK_PI,
 302                                                           private), 1, 0);
 303
 304             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 305                 && (INTERNAL_SYSCALL_ERRNO (e, __err) == ESRCH
 306                     || INTERNAL_SYSCALL_ERRNO (e, __err) == EDEADLK))
 307               {
 308                 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != EDEADLK
 309                         || (kind != PTHREAD_MUTEX_ERRORCHECK_NP
 310                             && kind != PTHREAD_MUTEX_RECURSIVE_NP));
 311                 /* ESRCH can happen only for non-robust PI mutexes where
 312                    the owner of the lock died.  */
 313                 assert (INTERNAL_SYSCALL_ERRNO (e, __err) != ESRCH || !robust);
 314
 315                 /* Delay the thread indefinitely.  */
 316                 while (1)
 317                   pause_not_cancel ();
 318               }
 319
 320             oldval = mutex->__data.__lock;
 321
 322             assert (robust || (oldval & FUTEX_OWNER_DIED) == 0);
 323           }
 324
 325         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 326           {
 327             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 328
 329             /* We got the mutex.  */
 330             mutex->__data.__count = 1;
 331             /* But it is inconsistent unless marked otherwise.  */
 332             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 333
 334             ENQUEUE_MUTEX_PI (mutex);
 335             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 336
 337             /* Note that we deliberately exit here.  If we fall
 338                through to the end of the function __nusers would be
 339                incremented which is not correct because the old owner
 340                has to be discounted.  If we are not supposed to
 341                increment __nusers we actually have to decrement it here.  */
 342 #ifdef NO_INCR
 343             --mutex->__data.__nusers;
 344 #endif
 345
 346             return EOWNERDEAD;
 347           }
 348
 349         if (robust
 350             && __builtin_expect (mutex->__data.__owner
 351                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 352           {
 353             /* This mutex is now not recoverable.  */
 354             mutex->__data.__count = 0;
 355
 356             INTERNAL_SYSCALL_DECL (__err);
 357             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 358                               __lll_private_flag (FUTEX_UNLOCK_PI,
 359                                                   PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
 360                               0, 0);
 361
 362             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 363             return ENOTRECOVERABLE;
 364           }
 365
 366         mutex->__data.__count = 1;
 367         if (robust)
 368           {
 369             ENQUEUE_MUTEX_PI (mutex);
 370             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 371           }
 372       }
 373       break;
 374
 375     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 376     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 377     case PTHREAD_MUTEX_PP_NORMAL_NP:
 378     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 379       {
 380         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 381
 382         oldval = mutex->__data.__lock;
 383
 384         /* Check whether we already hold the mutex.  */
 385         if (mutex->__data.__owner == id)
 386           {
 387             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 388               return EDEADLK;
 389
 390             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 391               {
 392                 /* Just bump the counter.  */
 393                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 394                   /* Overflow of the counter.  */
 395                   return EAGAIN;
 396
 397                 ++mutex->__data.__count;
 398
 399                 return 0;
 400               }
 401           }
 402
 403         int oldprio = -1, ceilval;
 404         do
 405           {
 406             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 407                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 408
 409             if (__pthread_current_priority () > ceiling)
 410               {
 411                 if (oldprio != -1)
 412                   __pthread_tpp_change_priority (oldprio, -1);
 413                 return EINVAL;
 414               }
 415
 416             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 417             if (retval)
 418               return retval;
 419
 420             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 421             oldprio = ceiling;
 422
 423             oldval
 424               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 425 #ifdef NO_INCR
 426                                                      ceilval | 2,
 427 #else
 428                                                      ceilval | 1,
 429 #endif
 430                                                      ceilval);
 431
 432             if (oldval == ceilval)
 433               break;
 434
 435             do
 436               {
 437                 oldval
 438                   = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 439                                                          ceilval | 2,
 440                                                          ceilval | 1);
 441
 442                 if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
 443                   break;
 444
 445                 if (oldval != ceilval)
 446                   lll_futex_wait (&mutex->__data.__lock, ceilval | 2,
 447                                   PTHREAD_MUTEX_PSHARED (mutex));
 448               }
 449             while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 450                                                         ceilval | 2, ceilval)
 451                    != ceilval);
 452           }
 453         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 454
 455         assert (mutex->__data.__owner == 0);
 456         mutex->__data.__count = 1;
 457       }
 458       break;
 459
 460     default:
 461       /* Correct code cannot set any other type.  */
 462       return EINVAL;
 463     }
 464
 465   /* Record the ownership.  */
 466   mutex->__data.__owner = id;
 467 #ifndef NO_INCR
 468   ++mutex->__data.__nusers;
 469 #endif
 470
 471   return 0;
 472 }
 473 #ifndef __pthread_mutex_lock
 474 strong_alias (__pthread_mutex_lock, pthread_mutex_lock)
 475 strong_alias (__pthread_mutex_lock, __pthread_mutex_lock_internal)
 476 #endif