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
  88                 = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
  89                                                        id, oldval);
  90
  91               if (newval != oldval)
  92                 {
  93                   oldval = newval;
  94                   goto again;
  95                 }
  96
  97               /* We got the mutex.  */
  98               mutex->__data.__count = 1;
  99               /* But it is inconsistent unless marked otherwise.  */
 100               mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 101
 102               ENQUEUE_MUTEX (mutex);
 103               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 104
 105               /* Note that we deliberately exist here.  If we fall
 106                  through to the end of the function __nusers would be
 107                  incremented which is not correct because the old
 108                  owner has to be discounted.  */
 109               return EOWNERDEAD;
 110             }
 111
 112           /* Check whether we already hold the mutex.  */
 113           if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 114             {
 115               if (mutex->__data.__kind
 116                   == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
 117                 {
 118                   THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 119                                  NULL);
 120                   return EDEADLK;
 121                 }
 122
 123               if (mutex->__data.__kind
 124                   == 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 (__builtin_expect (mutex->__data.__count + 1 == 0, 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_mutex_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_mutex_unlock (mutex->__data.__lock);
 155               THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 156               return ENOTRECOVERABLE;
 157             }
 158         }
 159       while ((oldval & FUTEX_OWNER_DIED) != 0);
 160
 161       ENQUEUE_MUTEX (mutex);
 162       THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 163
 164       mutex->__data.__owner = id;
 165       ++mutex->__data.__nusers;
 166       mutex->__data.__count = 1;
 167
 168       return 0;
 169
 170     case PTHREAD_MUTEX_PI_RECURSIVE_NP:
 171     case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
 172     case PTHREAD_MUTEX_PI_NORMAL_NP:
 173     case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
 174     case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
 175     case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
 176     case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
 177     case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
 178       {
 179         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 180         int robust = mutex->__data.__kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
 181
 182         if (robust)
 183           /* Note: robust PI futexes are signaled by setting bit 0.  */
 184           THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
 185                          (void *) (((uintptr_t) &mutex->__data.__list.__next)
 186                                    | 1));
 187
 188         oldval = mutex->__data.__lock;
 189
 190         /* Check whether we already hold the mutex.  */
 191         if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
 192           {
 193             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 194               {
 195                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 196                 return EDEADLK;
 197               }
 198
 199             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 200               {
 201                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 202
 203                 /* Just bump the counter.  */
 204                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 205                   /* Overflow of the counter.  */
 206                   return EAGAIN;
 207
 208                 ++mutex->__data.__count;
 209
 210                 return 0;
 211               }
 212           }
 213
 214         oldval
 215           = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 216                                                  id, 0);
 217
 218         if (oldval != 0)
 219           {
 220             if ((oldval & FUTEX_OWNER_DIED) == 0)
 221               {
 222                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 223
 224                 return EBUSY;
 225               }
 226
 227             assert (robust);
 228
 229             /* The mutex owner died.  The kernel will now take care of
 230                everything.  */
 231             INTERNAL_SYSCALL_DECL (__err);
 232             int e = INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 233                                       FUTEX_TRYLOCK_PI, 0, 0);
 234
 235             if (INTERNAL_SYSCALL_ERROR_P (e, __err)
 236                 && INTERNAL_SYSCALL_ERRNO (e, __err) == EWOULDBLOCK)
 237               {
 238                 THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 239
 240                 return EBUSY;
 241               }
 242
 243             oldval = mutex->__data.__lock;
 244           }
 245
 246         if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
 247           {
 248             atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
 249
 250             /* We got the mutex.  */
 251             mutex->__data.__count = 1;
 252             /* But it is inconsistent unless marked otherwise.  */
 253             mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
 254
 255             ENQUEUE_MUTEX (mutex);
 256             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 257
 258             /* Note that we deliberately exit here.  If we fall
 259                through to the end of the function __nusers would be
 260                incremented which is not correct because the old owner
 261                has to be discounted.  */
 262             return EOWNERDEAD;
 263           }
 264
 265         if (robust
 266             && __builtin_expect (mutex->__data.__owner
 267                                  == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 268           {
 269             /* This mutex is now not recoverable.  */
 270             mutex->__data.__count = 0;
 271
 272             INTERNAL_SYSCALL_DECL (__err);
 273             INTERNAL_SYSCALL (futex, __err, 4, &mutex->__data.__lock,
 274                               FUTEX_UNLOCK_PI, 0, 0);
 275
 276             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 277             return ENOTRECOVERABLE;
 278           }
 279
 280         if (robust)
 281           {
 282             ENQUEUE_MUTEX_PI (mutex);
 283             THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
 284           }
 285
 286         mutex->__data.__owner = id;
 287         ++mutex->__data.__nusers;
 288         mutex->__data.__count = 1;
 289
 290         return 0;
 291       }
 292
 293     case PTHREAD_MUTEX_PP_RECURSIVE_NP:
 294     case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
 295     case PTHREAD_MUTEX_PP_NORMAL_NP:
 296     case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
 297       {
 298         int kind = mutex->__data.__kind & PTHREAD_MUTEX_KIND_MASK_NP;
 299
 300         oldval = mutex->__data.__lock;
 301
 302         /* Check whether we already hold the mutex.  */
 303         if (mutex->__data.__owner == id)
 304           {
 305             if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
 306               return EDEADLK;
 307
 308             if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
 309               {
 310                 /* Just bump the counter.  */
 311                 if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
 312                   /* Overflow of the counter.  */
 313                   return EAGAIN;
 314
 315                 ++mutex->__data.__count;
 316
 317                 return 0;
 318               }
 319           }
 320
 321         int oldprio = -1, ceilval;
 322         do
 323           {
 324             int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
 325                           >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 326
 327             if (__pthread_current_priority () > ceiling)
 328               {
 329                 if (oldprio != -1)
 330                   __pthread_tpp_change_priority (oldprio, -1);
 331                 return EINVAL;
 332               }
 333
 334             int retval = __pthread_tpp_change_priority (oldprio, ceiling);
 335             if (retval)
 336               return retval;
 337
 338             ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
 339             oldprio = ceiling;
 340
 341             oldval
 342               = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
 343                                                      ceilval | 1, ceilval);
 344
 345             if (oldval == ceilval)
 346               break;
 347           }
 348         while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
 349
 350         if (oldval != ceilval)
 351           {
 352             __pthread_tpp_change_priority (oldprio, -1);
 353             break;
 354           }
 355
 356         assert (mutex->__data.__owner == 0);
 357         /* Record the ownership.  */
 358         mutex->__data.__owner = id;
 359         ++mutex->__data.__nusers;
 360         mutex->__data.__count = 1;
 361
 362         return 0;
 363       }
 364       break;
 365
 366     default:
 367       /* Correct code cannot set any other type.  */
 368       return EINVAL;
 369     }
 370
 371   return EBUSY;
 372 }
 373 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)