nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002, 2003, 2005, 2006, 2007 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 = id | (oldval & FUTEX_WAITERS);
  95
  96               newval
  97                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  98                                                        newval, oldval);
  99
 100               if (newval != oldval)
 101                 {
 102                   oldval = newval;
 103                   goto again;
 104                 }
 105
 106               /* We got the mutex.  */
 107               mutex->__data.__count = 1;
 108               /* But it is inconsistent unless marked otherwise.  */
 109               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 110
 111               ENQUEUE_MUTEX (mutex);
 112               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 113
 114               /* Note that we deliberately exist here.  If we fall
 115                  through to the end of the function __nusers would be
 116                  incremented which is not correct because the old
 117                  owner has to be discounted.  */
 118               return EOWNERDEAD;
 119             }
 120
 121           /* Check whether we already hold the mutex.  */
 122           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 123             {
 124               if (mutex->__data.__kind
 125                   == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 126                 {
 127                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 128                                  NULL);
 129                   return EDEADLK;
 130                 }
 131
 132               if (mutex->__data.__kind
 133                   == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 134                 {
 135                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 136                                  NULL);
 137
 138                   /* Just bump the counter.  */
 139                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 140                     /* Overflow of the counter.  */
 141                     return EAGAIN;
 142
 143                   ++mutex->__data.__count;
 144
 145                   return 0;
 146                 }
 147             }
 148
 149           oldval = lll_robust_mutex_trylock (mutex->__data.__lock, id);
 150           if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
 151             {
 152               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 153
 154               return EBUSY;
 155             }
 156
 157           if (__builtin_expect (mutex->__data.__owner
 158                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 159             {
 160               /* This mutex is now not recoverable.  */
 161               mutex->__data.__count = 0;
 162               if (oldval == id)
 163                 lll_mutex_unlock (mutex->__data.__lock);
 164               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 165               return ENOTRECOVERABLE;
 166             }
 167         }
 168       while ((oldval & FUTEX_OWNER_DIED) != 0);
 169
 170       ENQUEUE_MUTEX (mutex);
 171       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 172
 173       mutex->__data.__owner = id;
 174       ++mutex->__data.__nusers;
 175       mutex->__data.__count = 1;
 176
 177       return 0;
 178
 179     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 180     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 181     case PTHREAD_MUTEX_PI_NORMAL_NP:
 182     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 183     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 184     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 185     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 186     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 187       {
 188         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 189         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 190
 191         if (robust)
 192           /* Note: robust PI futexes are signaled by setting bit 0.  */
 193           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 194                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 195                                    | 1));
 196
 197         oldval = mutex->__data.__lock;
 198
 199         /* Check whether we already hold the mutex.  */
 200         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 201           {
 202             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 203               {
 204                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 205                 return EDEADLK;
 206               }
 207
 208             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 209               {
 210                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 211
 212                 /* Just bump the counter.  */
 213                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 214                   /* Overflow of the counter.  */
 215                   return EAGAIN;
 216
 217                 ++mutex->__data.__count;
 218
 219                 return 0;
 220               }
 221           }
 222
 223         oldval
 224           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 225                                                  id, 0);
 226
 227         if (oldval != 0)
 228           {
 229             if ((oldval & FUTEX_OWNER_DIED) == 0)
 230               {
 231                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 232
 233                 return EBUSY;
 234               }
 235
 236             assert (robust);
 237
 238             /* The mutex owner died.  The kernel will now take care of
 239                everything.  */
 240             INTERNAL_SYSCALL_DECL (__err);
 241             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 242                                       FUTEX_TRYLOCK_PI, 0, 0);
 243
 244             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 245                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 246               {
 247                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 248
 249                 return EBUSY;
 250               }
 251
 252             oldval = mutex->__data.__lock;
 253           }
 254
 255         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 256           {
 257             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 258
 259             /* We got the mutex.  */
 260             mutex->__data.__count = 1;
 261             /* But it is inconsistent unless marked otherwise.  */
 262             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 263
 264             ENQUEUE_MUTEX (mutex);
 265             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 266
 267             /* Note that we deliberately exit here.  If we fall
 268                through to the end of the function __nusers would be
 269                incremented which is not correct because the old owner
 270                has to be discounted.  */
 271             return EOWNERDEAD;
 272           }
 273
 274         if (robust
 275             && __builtin_expect (mutex->__data.__owner
 276                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 277           {
 278             /* This mutex is now not recoverable.  */
 279             mutex->__data.__count = 0;
 280
 281             INTERNAL_SYSCALL_DECL (__err);
 282             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 283                               FUTEX_UNLOCK_PI, 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)