nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002-2013 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <stdlib.h>
  22 #include "pthreadP.h"
  23 #include <lowlevellock.h>
  24
  25
  26 int
  27 __pthread_mutex_trylock (mutex)
  28      pthread_mutex_t *mutex;
  29 {
  30   int oldval;
  31   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  32
  33   switch (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex),
  34                             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_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     case PTHREAD_MUTEX_TIMED_NP:
  62     case PTHREAD_MUTEX_ADAPTIVE_NP:
  63       /* Normal mutex.  */
  64       if (lll_trylock (mutex->__data.__lock) != 0)
  65         break;
  66
  67       /* Record the ownership.  */
  68       mutex->__data.__owner = id;
  69       ++mutex->__data.__nusers;
  70
  71       return 0;
  72
  73     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
  74     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
  75     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
  76     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
  77       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
  78                      &mutex->__data.__list.__next);
  79
  80       oldval = mutex->__data.__lock;
  81       do
  82         {
  83         again:
  84           if ((oldval & FUTEX_OWNER_DIED) != 0)
  85             {
  86               /* The previous owner died.  Try locking the mutex.  */
  87               int newval = id | (oldval & FUTEX_WAITERS);
  88
  89               newval
  90                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  91                                                        newval, oldval);
  92
  93               if (newval != oldval)
  94                 {
  95                   oldval = newval;
  96                   goto again;
  97                 }
  98
  99               /* We got the mutex.  */
 100               mutex->__data.__count = 1;
 101               /* But it is inconsistent unless marked otherwise.  */
 102               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 103
 104               ENQUEUE_MUTEX (mutex);
 105               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 106
 107               /* Note that we deliberately exist here.  If we fall
 108                  through to the end of the function __nusers would be
 109                  incremented which is not correct because the old
 110                  owner has to be discounted.  */
 111               return EOWNERDEAD;
 112             }
 113
 114           /* Check whether we already hold the mutex.  */
 115           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 116             {
 117               int kind = PTHREAD_MUTEX_TYPE (mutex);
 118               if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 119                 {
 120                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 121                                  NULL);
 122                   return EDEADLK;
 123                 }
 124
 125               if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 126                 {
 127                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 128                                  NULL);
 129
 130                   /* Just bump the counter.  */
 131                   if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 132                     /* Overflow of the counter.  */
 133                     return EAGAIN;
 134
 135                   ++mutex->__data.__count;
 136
 137                   return 0;
 138                 }
 139             }
 140
 141           oldval = lll_robust_trylock (mutex->__data.__lock, id);
 142           if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
 143             {
 144               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 145
 146               return EBUSY;
 147             }
 148
 149           if (__builtin_expect (mutex->__data.__owner
 150                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 151             {
 152               /* This mutex is now not recoverable.  */
 153               mutex->__data.__count = 0;
 154               if (oldval == id)
 155                 lll_unlock (mutex->__data.__lock,
 156                             PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 157               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 158               return ENOTRECOVERABLE;
 159             }
 160         }
 161       while ((oldval & FUTEX_OWNER_DIED) != 0);
 162
 163       ENQUEUE_MUTEX (mutex);
 164       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 165
 166       mutex->__data.__owner = id;
 167       ++mutex->__data.__nusers;
 168       mutex->__data.__count = 1;
 169
 170       return 0;
 171
 172     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 173     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 174     case PTHREAD_MUTEX_PI_NORMAL_NP:
 175     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 176     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 177     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 178     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 179     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 180       {
 181         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 182         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 183
 184         if (robust)
 185           /* Note: robust PI futexes are signaled by setting bit 0.  */
 186           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 187                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 188                                    | 1));
 189
 190         oldval = mutex->__data.__lock;
 191
 192         /* Check whether we already hold the mutex.  */
 193         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 194           {
 195             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 196               {
 197                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 198                 return EDEADLK;
 199               }
 200
 201             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 202               {
 203                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 204
 205                 /* Just bump the counter.  */
 206                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 207                   /* Overflow of the counter.  */
 208                   return EAGAIN;
 209
 210                 ++mutex->__data.__count;
 211
 212                 return 0;
 213               }
 214           }
 215
 216         oldval
 217           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 218                                                  id, 0);
 219
 220         if (oldval != 0)
 221           {
 222             if ((oldval & FUTEX_OWNER_DIED) == 0)
 223               {
 224                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 225
 226                 return EBUSY;
 227               }
 228
 229             assert (robust);
 230
 231             /* The mutex owner died.  The kernel will now take care of
 232                everything.  */
 233             int private = (robust
 234                            ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
 235                            : PTHREAD_MUTEX_PSHARED (mutex));
 236             INTERNAL_SYSCALL_DECL (__err);
 237             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 238                                       __lll_private_flag (FUTEX_TRYLOCK_PI,
 239                                                           private), 0, 0);
 240
 241             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 242                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 243               {
 244                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 245
 246                 return EBUSY;
 247               }
 248
 249             oldval = mutex->__data.__lock;
 250           }
 251
 252         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 253           {
 254             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 255
 256             /* We got the mutex.  */
 257             mutex->__data.__count = 1;
 258             /* But it is inconsistent unless marked otherwise.  */
 259             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 260
 261             ENQUEUE_MUTEX (mutex);
 262             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 263
 264             /* Note that we deliberately exit here.  If we fall
 265                through to the end of the function __nusers would be
 266                incremented which is not correct because the old owner
 267                has to be discounted.  */
 268             return EOWNERDEAD;
 269           }
 270
 271         if (robust
 272             && __builtin_expect (mutex->__data.__owner
 273                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 274           {
 275             /* This mutex is now not recoverable.  */
 276             mutex->__data.__count = 0;
 277
 278             INTERNAL_SYSCALL_DECL (__err);
 279             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 280                               __lll_private_flag (FUTEX_UNLOCK_PI,
 281                                                   PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
 282                               0, 0);
 283
 284             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 285             return ENOTRECOVERABLE;
 286           }
 287
 288         if (robust)
 289           {
 290             ENQUEUE_MUTEX_PI (mutex);
 291             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 292           }
 293
 294         mutex->__data.__owner = id;
 295         ++mutex->__data.__nusers;
 296         mutex->__data.__count = 1;
 297
 298         return 0;
 299       }
 300
 301     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 302     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 303     case PTHREAD_MUTEX_PP_NORMAL_NP:
 304     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 305       {
 306         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 307
 308         oldval = mutex->__data.__lock;
 309
 310         /* Check whether we already hold the mutex.  */
 311         if (mutex->__data.__owner == id)
 312           {
 313             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 314               return EDEADLK;
 315
 316             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 317               {
 318                 /* Just bump the counter.  */
 319                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 320                   /* Overflow of the counter.  */
 321                   return EAGAIN;
 322
 323                 ++mutex->__data.__count;
 324
 325                 return 0;
 326               }
 327           }
 328
 329         int oldprio = -1, ceilval;
 330         do
 331           {
 332             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 333                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 334
 335             if (__pthread_current_priority () > ceiling)
 336               {
 337                 if (oldprio != -1)
 338                   __pthread_tpp_change_priority (oldprio, -1);
 339                 return EINVAL;
 340               }
 341
 342             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 343             if (retval)
 344               return retval;
 345
 346             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 347             oldprio = ceiling;
 348
 349             oldval
 350               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 351                                                      ceilval | 1, ceilval);
 352
 353             if (oldval == ceilval)
 354               break;
 355           }
 356         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 357
 358         if (oldval != ceilval)
 359           {
 360             __pthread_tpp_change_priority (oldprio, -1);
 361             break;
 362           }
 363
 364         assert (mutex->__data.__owner == 0);
 365         /* Record the ownership.  */
 366         mutex->__data.__owner = id;
 367         ++mutex->__data.__nusers;
 368         mutex->__data.__count = 1;
 369
 370         return 0;
 371       }
 372       break;
 373
 374     default:
 375       /* Correct code cannot set any other type.  */
 376       return EINVAL;
 377     }
 378
 379   return EBUSY;
 380 }
 381 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)