fbtl/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 (pthread_mutex_t *mutex)
  28 {
  29   int oldval;
  30   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  31
  32   switch (__builtin_expect (PTHREAD_MUTEX_TYPE (mutex),
  33                             PTHREAD_MUTEX_TIMED_NP))
  34     {
  35       /* Recursive mutex.  */
  36     case PTHREAD_MUTEX_RECURSIVE_NP:
  37       /* Check whether we already hold the mutex.  */
  38       if (mutex->__data.__owner == id)
  39         {
  40           /* Just bump the counter.  */
  41           if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
  42             /* Overflow of the counter.  */
  43             return EAGAIN;
  44
  45           ++mutex->__data.__count;
  46           return 0;
  47         }
  48
  49       if (lll_trylock (mutex->__data.__lock) == 0)
  50         {
  51           /* Record the ownership.  */
  52           mutex->__data.__owner = id;
  53           mutex->__data.__count = 1;
  54           ++mutex->__data.__nusers;
  55           return 0;
  56         }
  57       break;
  58
  59     case PTHREAD_MUTEX_ERRORCHECK_NP:
  60     case PTHREAD_MUTEX_TIMED_NP:
  61     case PTHREAD_MUTEX_ADAPTIVE_NP:
  62       /* Normal mutex.  */
  63       if (lll_trylock (mutex->__data.__lock) != 0)
  64         break;
  65
  66       /* Record the ownership.  */
  67       mutex->__data.__owner = id;
  68       ++mutex->__data.__nusers;
  69
  70       return 0;
  71 #if 0
  72     case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
  73     case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
  74     case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
  75     case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
  76       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
  77                      &mutex->__data.__list.__next);
  78
  79       oldval = mutex->__data.__lock;
  80       do
  81         {
  82         again:
  83           if ((oldval & FUTEX_OWNER_DIED) != 0)
  84             {
  85               /* The previous owner died.  Try locking the mutex.  */
  86               int newval = id | (oldval & FUTEX_WAITERS);
  87
  88               newval
  89                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  90                                                        newval, oldval);
  91
  92               if (newval != oldval)
  93                 {
  94                   oldval = newval;
  95                   goto again;
  96                 }
  97
  98               /* We got the mutex.  */
  99               mutex->__data.__count = 1;
 100               /* But it is inconsistent unless marked otherwise.  */
 101               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 102
 103               ENQUEUE_MUTEX (mutex);
 104               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 105
 106               /* Note that we deliberately exist here.  If we fall
 107                  through to the end of the function __nusers would be
 108                  incremented which is not correct because the old
 109                  owner has to be discounted.  */
 110               return EOWNERDEAD;
 111             }
 112
 113           /* Check whether we already hold the mutex.  */
 114           if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
 115             {
 116               int kind = PTHREAD_MUTEX_TYPE (mutex);
 117               if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 118                 {
 119                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 120                                  NULL);
 121                   return EDEADLK;
 122                 }
 123
 124               if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
 125                 {
 126                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 127                                  NULL);
 128
 129                   /* Just bump the counter.  */
 130                   if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
 131                     /* Overflow of the counter.  */
 132                     return EAGAIN;
 133
 134                   ++mutex->__data.__count;
 135
 136                   return 0;
 137                 }
 138             }
 139
 140           oldval = lll_robust_trylock (mutex->__data.__lock, id);
 141           if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
 142             {
 143               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 144
 145               return EBUSY;
 146             }
 147
 148           if (__builtin_expect (mutex->__data.__owner
 149                                 == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 150             {
 151               /* This mutex is now not recoverable.  */
 152               mutex->__data.__count = 0;
 153               if (oldval == id)
 154                 lll_unlock (mutex->__data.__lock,
 155                             PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
 156               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 157               return ENOTRECOVERABLE;
 158             }
 159         }
 160       while ((oldval & FUTEX_OWNER_DIED) != 0);
 161
 162       ENQUEUE_MUTEX (mutex);
 163       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 164
 165       mutex->__data.__owner = id;
 166       ++mutex->__data.__nusers;
 167       mutex->__data.__count = 1;
 168
 169       return 0;
 170
 171     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 172     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 173     case PTHREAD_MUTEX_PI_NORMAL_NP:
 174     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 175     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 176     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 177     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 178     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 179       {
 180         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 181         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 182
 183         if (robust)
 184           /* Note: robust PI futexes are signaled by setting bit 0.  */
 185           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 186                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 187                                    | 1));
 188
 189         oldval = mutex->__data.__lock;
 190
 191         /* Check whether we already hold the mutex.  */
 192         if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
 193           {
 194             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 195               {
 196                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 197                 return EDEADLK;
 198               }
 199
 200             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 201               {
 202                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 203
 204                 /* Just bump the counter.  */
 205                 if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
 206                   /* Overflow of the counter.  */
 207                   return EAGAIN;
 208
 209                 ++mutex->__data.__count;
 210
 211                 return 0;
 212               }
 213           }
 214
 215         oldval
 216           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 217                                                  id, 0);
 218
 219         if (oldval != 0)
 220           {
 221             if ((oldval & FUTEX_OWNER_DIED) == 0)
 222               {
 223                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 224
 225                 return EBUSY;
 226               }
 227
 228             assert (robust);
 229
 230             /* The mutex owner died.  The kernel will now take care of
 231                everything.  */
 232             int private = (robust
 233                            ? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
 234                            : PTHREAD_MUTEX_PSHARED (mutex));
 235             INTERNAL_SYSCALL_DECL (__err);
 236             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 237                                       __lll_private_flag (FUTEX_TRYLOCK_PI,
 238                                                           private), 0, 0);
 239
 240             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 241                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 242               {
 243                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 244
 245                 return EBUSY;
 246               }
 247
 248             oldval = mutex->__data.__lock;
 249           }
 250
 251         if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
 252           {
 253             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 254
 255             /* We got the mutex.  */
 256             mutex->__data.__count = 1;
 257             /* But it is inconsistent unless marked otherwise.  */
 258             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 259
 260             ENQUEUE_MUTEX (mutex);
 261             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 262
 263             /* Note that we deliberately exit here.  If we fall
 264                through to the end of the function __nusers would be
 265                incremented which is not correct because the old owner
 266                has to be discounted.  */
 267             return EOWNERDEAD;
 268           }
 269
 270         if (robust
 271             && __builtin_expect (mutex->__data.__owner
 272                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 273           {
 274             /* This mutex is now not recoverable.  */
 275             mutex->__data.__count = 0;
 276
 277             INTERNAL_SYSCALL_DECL (__err);
 278             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 279                               __lll_private_flag (FUTEX_UNLOCK_PI,
 280                                                   PTHREAD_ROBUST_MUTEX_PSHARED (mutex)),
 281                               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 (__glibc_unlikely (mutex->__data.__count + 1 == 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 #endif
 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)