nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002, 2003, 2005-2007, 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 "pthreadP.h"
  24 #include <lowlevellock.h>
  25
  26
  27 int
  28 __pthread_mutex_trylock (mutex)
  29      pthread_mutex_t *mutex;
  30 {
  31   int oldval;
  32   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  33
  34   switch (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex),
  35                             PTHREAD_MUTEX_TIMED_NP))
  36     {
  37       /* Recursive mutex.  */
  38     case PTHREAD_MUTEX_RECURSIVE_NP:
  39       /* Check whether we already hold the mutex.  */
  40       if (mutex->__data.__owner == id)
  41         {
  42           /* Just bump the counter.  */
  43           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  44             /* Overflow of the counter.  */
  45             return EAGAIN;
  46
  47           ++mutex->__data.__count;
  48           return 0;
  49         }
  50
  51       if (lll_trylock (mutex->__data.__lock) == 0)
  52         {
  53           /* Record the ownership.  */
  54           mutex->__data.__owner = id;
  55           mutex->__data.__count = 1;
  56           ++mutex->__data.__nusers;
  57           return 0;
  58         }
  59       break;
  60
  61     case PTHREAD_MUTEX_ERRORCHECK_NP:
  62     case PTHREAD_MUTEX_TIMED_NP:
  63     case PTHREAD_MUTEX_ADAPTIVE_NP:
  64       /* Normal mutex.  */
  65       if (lll_trylock (mutex->__data.__lock) != 0)
  66         break;
  67
  68       /* Record the ownership.  */
  69       mutex->__data.__owner = id;
  70       ++mutex->__data.__nusers;
  71
  72       return 0;
  73
  74     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
  75     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
  76     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
  77     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
  78       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
  79                      &mutex->__data.__list.__next);
  80
  81       oldval = mutex->__data.__lock;
  82       do
  83         {
  84         again:
  85           if ((oldval & FUTEX_OWNER_DIED) != 0)
  86             {
  87               /* The previous owner died.  Try locking the mutex.  */
  88               int newval = id | (oldval & FUTEX_WAITERS);
  89
  90               newval
  91                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  92                                                        newval, oldval);
  93
  94               if (newval != oldval)
  95                 {
  96                   oldval = newval;
  97                   goto again;
  98                 }
  99
 100               /* We got the mutex.  */
 101               mutex->__data.__count = 1;
 102               /* But it is inconsistent unless marked otherwise.  */
 103               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 104
 105               ENQUEUE_MUTEX (mutex);
 106               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 107
 108               /* Note that we deliberately exist here.  If we fall
 109                  through to the end of the function __nusers would be
 110                  incremented which is not correct because the old
 111                  owner has to be discounted.  */
 112               return EOWNERDEAD;
 113             }
 114
 115           /* Check whether we already hold the mutex.  */
 116           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 117             {
 118               int kind = PTHREAD_MUTEX_TYPE (mutex);
 119               if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 120                 {
 121                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 122                                  NULL);
 123                   return EDEADLK;
 124                 }
 125
 126               if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 127                 {
 128                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 129                                  NULL);
 130
 131                   /* Just bump the counter.  */
 132                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 133                     /* Overflow of the counter.  */
 134                     return EAGAIN;
 135
 136                   ++mutex->__data.__count;
 137
 138                   return 0;
 139                 }
 140             }
 141
 142           oldval = lll_robust_trylock (mutex->__data.__lock, id);
 143           if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
 144             {
 145               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 146
 147               return EBUSY;
 148             }
 149
 150           if (__builtin_expect (mutex->__data.__owner
 151                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 152             {
 153               /* This mutex is now not recoverable.  */
 154               mutex->__data.__count = 0;
 155               if (oldval == id)
 156                 lll_unlock (mutex->__data.__lock,
 157                             PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 158               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 159               return ENOTRECOVERABLE;
 160             }
 161         }
 162       while ((oldval & FUTEX_OWNER_DIED) != 0);
 163
 164       ENQUEUE_MUTEX (mutex);
 165       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 166
 167       mutex->__data.__owner = id;
 168       ++mutex->__data.__nusers;
 169       mutex->__data.__count = 1;
 170
 171       return 0;
 172
 173     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 174     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 175     case PTHREAD_MUTEX_PI_NORMAL_NP:
 176     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 177     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 178     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 179     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 180     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 181       {
 182         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 183         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 184
 185         if (robust)
 186           /* Note: robust PI futexes are signaled by setting bit 0.  */
 187           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 188                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 189                                    | 1));
 190
 191         oldval = mutex->__data.__lock;
 192
 193         /* Check whether we already hold the mutex.  */
 194         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 195           {
 196             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 197               {
 198                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 199                 return EDEADLK;
 200               }
 201
 202             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 203               {
 204                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 205
 206                 /* Just bump the counter.  */
 207                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 208                   /* Overflow of the counter.  */
 209                   return EAGAIN;
 210
 211                 ++mutex->__data.__count;
 212
 213                 return 0;
 214               }
 215           }
 216
 217         oldval
 218           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 219                                                  id, 0);
 220
 221         if (oldval != 0)
 222           {
 223             if ((oldval & FUTEX_OWNER_DIED) == 0)
 224               {
 225                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 226
 227                 return EBUSY;
 228               }
 229
 230             assert (robust);
 231
 232             /* The mutex owner died.  The kernel will now take care of
 233                everything.  */
 234             int private = (robust
 235                            ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
 236                            : PTHREAD_MUTEX_PSHARED (mutex));
 237             INTERNAL_SYSCALL_DECL (__err);
 238             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 239                                       __lll_private_flag (FUTEX_TRYLOCK_PI,
 240                                                           private), 0, 0);
 241
 242             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 243                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 244               {
 245                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 246
 247                 return EBUSY;
 248               }
 249
 250             oldval = mutex->__data.__lock;
 251           }
 252
 253         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 254           {
 255             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 256
 257             /* We got the mutex.  */
 258             mutex->__data.__count = 1;
 259             /* But it is inconsistent unless marked otherwise.  */
 260             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 261
 262             ENQUEUE_MUTEX (mutex);
 263             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 264
 265             /* Note that we deliberately exit here.  If we fall
 266                through to the end of the function __nusers would be
 267                incremented which is not correct because the old owner
 268                has to be discounted.  */
 269             return EOWNERDEAD;
 270           }
 271
 272         if (robust
 273             && __builtin_expect (mutex->__data.__owner
 274                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 275           {
 276             /* This mutex is now not recoverable.  */
 277             mutex->__data.__count = 0;
 278
 279             INTERNAL_SYSCALL_DECL (__err);
 280             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 281                               __lll_private_flag (FUTEX_UNLOCK_PI,
 282                                                   PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
 283                               0, 0);
 284
 285             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 286             return ENOTRECOVERABLE;
 287           }
 288
 289         if (robust)
 290           {
 291             ENQUEUE_MUTEX_PI (mutex);
 292             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 293           }
 294
 295         mutex->__data.__owner = id;
 296         ++mutex->__data.__nusers;
 297         mutex->__data.__count = 1;
 298
 299         return 0;
 300       }
 301
 302     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 303     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 304     case PTHREAD_MUTEX_PP_NORMAL_NP:
 305     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 306       {
 307         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 308
 309         oldval = mutex->__data.__lock;
 310
 311         /* Check whether we already hold the mutex.  */
 312         if (mutex->__data.__owner == id)
 313           {
 314             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 315               return EDEADLK;
 316
 317             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 318               {
 319                 /* Just bump the counter.  */
 320                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 321                   /* Overflow of the counter.  */
 322                   return EAGAIN;
 323
 324                 ++mutex->__data.__count;
 325
 326                 return 0;
 327               }
 328           }
 329
 330         int oldprio = -1, ceilval;
 331         do
 332           {
 333             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 334                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 335
 336             if (__pthread_current_priority () > ceiling)
 337               {
 338                 if (oldprio != -1)
 339                   __pthread_tpp_change_priority (oldprio, -1);
 340                 return EINVAL;
 341               }
 342
 343             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 344             if (retval)
 345               return retval;
 346
 347             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 348             oldprio = ceiling;
 349
 350             oldval
 351               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 352                                                      ceilval | 1, ceilval);
 353
 354             if (oldval == ceilval)
 355               break;
 356           }
 357         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 358
 359         if (oldval != ceilval)
 360           {
 361             __pthread_tpp_change_priority (oldprio, -1);
 362             break;
 363           }
 364
 365         assert (mutex->__data.__owner == 0);
 366         /* Record the ownership.  */
 367         mutex->__data.__owner = id;
 368         ++mutex->__data.__nusers;
 369         mutex->__data.__count = 1;
 370
 371         return 0;
 372       }
 373       break;
 374
 375     default:
 376       /* Correct code cannot set any other type.  */
 377       return EINVAL;
 378     }
 379
 380   return EBUSY;
 381 }
 382 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)