nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002, 2003, 2005 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   pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
  32
  33   switch (__builtin_expect (mutex->__data.__kind, 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 (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  42             /* Overflow of the counter.  */
  43             return EAGAIN;
  44
  45           ++mutex->__data.__count;
  46           return 0;
  47         }
  48
  49       if (lll_mutex_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       /* Check whether we already hold the mutex.  */
  61       if (__builtin_expect (mutex->__data.__owner == id, 0))
  62         return EDEADLK;
  63
  64       /* FALLTHROUGH */
  65
  66     case PTHREAD_MUTEX_TIMED_NP:
  67     case PTHREAD_MUTEX_ADAPTIVE_NP:
  68       /* Normal mutex.  */
  69       if (lll_mutex_trylock (mutex->__data.__lock) != 0)
  70         break;
  71
  72       /* Record the ownership.  */
  73       mutex->__data.__owner = id;
  74       ++mutex->__data.__nusers;
  75
  76       return 0;
  77
  78
  79     case PTHREAD_MUTEX_ROBUST_PRIVATE_RECURSIVE_NP:
  80       /* Check whether we already hold the mutex.  */
  81       if (abs (mutex->__data.__owner) == id)
  82         {
  83           /* Just bump the counter.  */
  84           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  85             /* Overflow of the counter.  */
  86             return EAGAIN;
  87
  88           ++mutex->__data.__count;
  89
  90           return 0;
  91         }
  92
  93       /* We have to get the mutex.  */
  94       if (lll_mutex_trylock (mutex->__data.__lock) == 0)
  95         {
  96           mutex->__data.__count = 1;
  97
  98           goto robust;
  99         }
 100
 101       break;
 102
 103     case PTHREAD_MUTEX_ROBUST_PRIVATE_ERRORCHECK_NP:
 104       /* Check whether we already hold the mutex.  */
 105       if (__builtin_expect (abs (mutex->__data.__owner) == id, 0))
 106         return EDEADLK;
 107
 108       /* FALLTHROUGH */
 109
 110     case PTHREAD_MUTEX_ROBUST_PRIVATE_NP:
 111     case PTHREAD_MUTEX_ROBUST_PRIVATE_ADAPTIVE_NP:
 112       if (lll_mutex_trylock (mutex->__data.__lock) != 0)
 113         break;
 114
 115     robust:
 116       if (__builtin_expect (mutex->__data.__owner
 117                             == PTHREAD_MUTEX_NOTRECOVERABLE, 0))
 118         {
 119           /* This mutex is now not recoverable.  */
 120           mutex->__data.__count = 0;
 121           lll_mutex_unlock (mutex->__data.__lock);
 122           return ENOTRECOVERABLE;
 123         }
 124
 125       /* This mutex is either healthy or we can try to recover it.  */
 126       assert (mutex->__data.__owner == 0
 127               || mutex->__data.__owner == PTHREAD_MUTEX_OWNERDEAD);
 128
 129       /* Record the ownership.  */
 130       int retval = 0;
 131       if (__builtin_expect (mutex->__data.__owner
 132                             == PTHREAD_MUTEX_OWNERDEAD, 0))
 133         {
 134           retval = EOWNERDEAD;
 135           /* We signal ownership of a not yet recovered robust
 136              mutex by storing the negative thread ID.  */
 137           id = -id;
 138         }
 139
 140       ENQUEUE_MUTEX (mutex);
 141
 142       mutex->__data.__owner = id;
 143       ++mutex->__data.__nusers;
 144
 145       return retval
 146 ;
 147     default:
 148       /* Correct code cannot set any other type.  */
 149       return EINVAL;
 150     }
 151
 152   return EBUSY;
 153 }
 154 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)