nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002, 2003, 2005, 2006 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 (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
  35     {
  36       /* Recursive mutex.  */
  37     case PTHREAD_MUTEX_RECURSIVE_NP:
  38       /* Check whether we already hold the mutex.  */
  39       if (mutex->__data.__owner == id)
  40         {
  41           /* Just bump the counter.  */
  42           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  43             /* Overflow of the counter.  */
  44             return EAGAIN;
  45
  46           ++mutex->__data.__count;
  47           return 0;
  48         }
  49
  50       if (lll_mutex_trylock (mutex->__data.__lock) == 0)
  51         {
  52           /* Record the ownership.  */
  53           mutex->__data.__owner = id;
  54           mutex->__data.__count = 1;
  55           ++mutex->__data.__nusers;
  56           return 0;
  57         }
  58       break;
  59
  60     case PTHREAD_MUTEX_ERRORCHECK_NP:
  61       /* Check whether we already hold the mutex.  */
  62       if (__builtin_expect (mutex->__data.__owner == id, 0))
  63         return EDEADLK;
  64
  65       /* FALLTHROUGH */
  66
  67     case PTHREAD_MUTEX_TIMED_NP:
  68     case PTHREAD_MUTEX_ADAPTIVE_NP:
  69       /* Normal mutex.  */
  70       if (lll_mutex_trylock (mutex->__data.__lock) != 0)
  71         break;
  72
  73       /* Record the ownership.  */
  74       mutex->__data.__owner = id;
  75       ++mutex->__data.__nusers;
  76
  77       return 0;
  78
  79
  80     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
  81     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
  82     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
  83     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
  84       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
  85                      &mutex->__data.__list.__next);
  86
  87       oldval = mutex->__data.__lock;
  88       do
  89         {
  90         again:
  91           if ((oldval & FUTEX_OWNER_DIED) != 0)
  92             {
  93               /* The previous owner died.  Try locking the mutex.  */
  94               int newval
  95                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  96                                                        id, oldval);
  97
  98               if (newval != oldval)
  99                 {
 100                   oldval = newval;
 101                   goto again;
 102                 }
 103
 104               /* We got the mutex.  */
 105               mutex->__data.__count = 1;
 106               /* But it is inconsistent unless marked otherwise.  */
 107               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 108
 109               ENQUEUE_MUTEX (mutex);
 110               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 111
 112               /* Note that we deliberately exist here.  If we fall
 113                  through to the end of the function __nusers would be
 114                  incremented which is not correct because the old
 115                  owner has to be discounted.  */
 116               return EOWNERDEAD;
 117             }
 118
 119           /* Check whether we already hold the mutex.  */
 120           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 121             {
 122               if (mutex->__data.__kind
 123                   == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 124                 {
 125                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 126                                  NULL);
 127                   return EDEADLK;
 128                 }
 129
 130               if (mutex->__data.__kind
 131                   == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 132                 {
 133                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 134                                  NULL);
 135
 136                   /* Just bump the counter.  */
 137                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 138                     /* Overflow of the counter.  */
 139                     return EAGAIN;
 140
 141                   ++mutex->__data.__count;
 142
 143                   return 0;
 144                 }
 145             }
 146
 147           oldval = lll_robust_mutex_trylock (mutex->__data.__lock, id);
 148           if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
 149             {
 150               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 151
 152               return EBUSY;
 153             }
 154
 155           if (__builtin_expect (mutex->__data.__owner
 156                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 157             {
 158               /* This mutex is now not recoverable.  */
 159               mutex->__data.__count = 0;
 160               if (oldval == id)
 161                 lll_mutex_unlock (mutex->__data.__lock);
 162               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 163               return ENOTRECOVERABLE;
 164             }
 165         }
 166       while ((oldval & FUTEX_OWNER_DIED) != 0);
 167
 168       ENQUEUE_MUTEX (mutex);
 169       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 170
 171       mutex->__data.__owner = id;
 172       ++mutex->__data.__nusers;
 173       mutex->__data.__count = 1;
 174
 175       return 0;
 176
 177     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 178     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 179     case PTHREAD_MUTEX_PI_NORMAL_NP:
 180     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 181     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 182     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 183     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 184     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 185       {
 186         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 187         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 188
 189         if (robust)
 190           /* Note: robust PI futexes are signaled by setting bit 0.  */
 191           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 192                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 193                                    | 1));
 194
 195         oldval = mutex->__data.__lock;
 196
 197         /* Check whether we already hold the mutex.  */
 198         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 199           {
 200             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 201               {
 202                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 203                 return EDEADLK;
 204               }
 205
 206             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 207               {
 208                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, 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
 222           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 223                                                  id, 0);
 224
 225         if (oldval != 0)
 226           {
 227             if ((oldval & FUTEX_OWNER_DIED) == 0)
 228               {
 229                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 230
 231                 return EBUSY;
 232               }
 233
 234             assert (robust);
 235
 236             /* The mutex owner died.  The kernel will now take care of
 237                everything.  */
 238             INTERNAL_SYSCALL_DECL (__err);
 239             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 240                                       FUTEX_TRYLOCK_PI, 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                               FUTEX_UNLOCK_PI, 0, 0);
 282
 283             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 284             return ENOTRECOVERABLE;
 285           }
 286
 287         if (robust)
 288           {
 289             ENQUEUE_MUTEX_PI (mutex);
 290             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 291           }
 292
 293         mutex->__data.__owner = id;
 294         ++mutex->__data.__nusers;
 295         mutex->__data.__count = 1;
 296
 297         return 0;
 298       }
 299
 300     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 301     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 302     case PTHREAD_MUTEX_PP_NORMAL_NP:
 303     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 304       {
 305         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 306
 307         oldval = mutex->__data.__lock;
 308
 309         /* Check whether we already hold the mutex.  */
 310         if (mutex->__data.__owner == id)
 311           {
 312             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 313               return EDEADLK;
 314
 315             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 316               {
 317                 /* Just bump the counter.  */
 318                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 319                   /* Overflow of the counter.  */
 320                   return EAGAIN;
 321
 322                 ++mutex->__data.__count;
 323
 324                 return 0;
 325               }
 326           }
 327
 328         int oldprio = -1, ceilval;
 329         do
 330           {
 331             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 332                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 333
 334             if (__pthread_current_priority () > ceiling)
 335               {
 336                 if (oldprio != -1)
 337                   __pthread_tpp_change_priority (oldprio, -1);
 338                 return EINVAL;
 339               }
 340
 341             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 342             if (retval)
 343               return retval;
 344
 345             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 346             oldprio = ceiling;
 347
 348             oldval
 349               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 350                                                      ceilval | 1, ceilval);
 351
 352             if (oldval == ceilval)
 353               break;
 354           }
 355         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 356
 357         if (oldval != ceilval)
 358           {
 359             __pthread_tpp_change_priority (oldprio, -1);
 360             break;
 361           }
 362
 363         assert (mutex->__data.__owner == 0);
 364         /* Record the ownership.  */
 365         mutex->__data.__owner = id;
 366         ++mutex->__data.__nusers;
 367         mutex->__data.__count = 1;
 368
 369         return 0;
 370       }
 371       break;
 372
 373     default:
 374       /* Correct code cannot set any other type.  */
 375       return EINVAL;
 376     }
 377
 378   return EBUSY;
 379 }
 380 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)