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     case PTHREAD_MUTEX_TIMED_NP:
  62     case PTHREAD_MUTEX_ADAPTIVE_NP:
  63       /* Normal mutex.  */
  64       if (lll_mutex_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               if (mutex->__data.__kind
 118                   == 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 (mutex->__data.__kind
 126                   == 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_mutex_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_mutex_unlock (mutex->__data.__lock);
 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             INTERNAL_SYSCALL_DECL (__err);
 234             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 235                                       FUTEX_TRYLOCK_PI, 0, 0);
 236
 237             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 238                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 239               {
 240                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 241
 242                 return EBUSY;
 243               }
 244
 245             oldval = mutex->__data.__lock;
 246           }
 247
 248         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 249           {
 250             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 251
 252             /* We got the mutex.  */
 253             mutex->__data.__count = 1;
 254             /* But it is inconsistent unless marked otherwise.  */
 255             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 256
 257             ENQUEUE_MUTEX (mutex);
 258             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 259
 260             /* Note that we deliberately exit here.  If we fall
 261                through to the end of the function __nusers would be
 262                incremented which is not correct because the old owner
 263                has to be discounted.  */
 264             return EOWNERDEAD;
 265           }
 266
 267         if (robust
 268             && __builtin_expect (mutex->__data.__owner
 269                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 270           {
 271             /* This mutex is now not recoverable.  */
 272             mutex->__data.__count = 0;
 273
 274             INTERNAL_SYSCALL_DECL (__err);
 275             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 276                               FUTEX_UNLOCK_PI, 0, 0);
 277
 278             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 279             return ENOTRECOVERABLE;
 280           }
 281
 282         if (robust)
 283           {
 284             ENQUEUE_MUTEX_PI (mutex);
 285             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 286           }
 287
 288         mutex->__data.__owner = id;
 289         ++mutex->__data.__nusers;
 290         mutex->__data.__count = 1;
 291
 292         return 0;
 293       }
 294
 295     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 296     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 297     case PTHREAD_MUTEX_PP_NORMAL_NP:
 298     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 299       {
 300         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 301
 302         oldval = mutex->__data.__lock;
 303
 304         /* Check whether we already hold the mutex.  */
 305         if (mutex->__data.__owner == id)
 306           {
 307             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 308               return EDEADLK;
 309
 310             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 311               {
 312                 /* Just bump the counter.  */
 313                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 314                   /* Overflow of the counter.  */
 315                   return EAGAIN;
 316
 317                 ++mutex->__data.__count;
 318
 319                 return 0;
 320               }
 321           }
 322
 323         int oldprio = -1, ceilval;
 324         do
 325           {
 326             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 327                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 328
 329             if (__pthread_current_priority () > ceiling)
 330               {
 331                 if (oldprio != -1)
 332                   __pthread_tpp_change_priority (oldprio, -1);
 333                 return EINVAL;
 334               }
 335
 336             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 337             if (retval)
 338               return retval;
 339
 340             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 341             oldprio = ceiling;
 342
 343             oldval
 344               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 345                                                      ceilval | 1, ceilval);
 346
 347             if (oldval == ceilval)
 348               break;
 349           }
 350         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 351
 352         if (oldval != ceilval)
 353           {
 354             __pthread_tpp_change_priority (oldprio, -1);
 355             break;
 356           }
 357
 358         assert (mutex->__data.__owner == 0);
 359         /* Record the ownership.  */
 360         mutex->__data.__owner = id;
 361         ++mutex->__data.__nusers;
 362         mutex->__data.__count = 1;
 363
 364         return 0;
 365       }
 366       break;
 367
 368     default:
 369       /* Correct code cannot set any other type.  */
 370       return EINVAL;
 371     }
 372
 373   return EBUSY;
 374 }
 375 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)