nptl/pthread_mutex_trylock.c

   1 /* Copyright (C) 2002, 2003 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 <errno.h>
  21 #include "pthreadP.h"
  22 #include <lowlevellock.h>
  23
  24
  25 int
  26 __pthread_mutex_trylock (mutex)
  27      pthread_mutex_t *mutex;
  28 {
  29   pid_t id;
  30
  31   switch (__builtin_expect (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
  32     {
  33       /* Recursive mutex.  */
  34     case PTHREAD_MUTEX_RECURSIVE_NP:
  35       id = THREAD_GETMEM (THREAD_SELF, tid);
  36       /* Check whether we already hold the mutex.  */
  37       if (mutex->__data.__owner == id)
  38         {
  39           /* Just bump the counter.  */
  40           if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
  41             /* Overflow of the counter.  */
  42             return EAGAIN;
  43
  44           ++mutex->__data.__count;
  45           return 0;
  46         }
  47
  48       if (lll_mutex_trylock (mutex->__data.__lock) == 0)
  49         {
  50           /* Record the ownership.  */
  51           mutex->__data.__owner = id;
  52           mutex->__data.__count = 1;
  53           ++mutex->__data.__nusers;
  54           return 0;
  55         }
  56       break;
  57
  58     case PTHREAD_MUTEX_ERRORCHECK_NP:
  59       /* Error checking mutex.  We do not check for deadlocks.  */
  60     default:
  61       /* Correct code cannot set any other type.  */
  62     case PTHREAD_MUTEX_TIMED_NP:
  63     case PTHREAD_MUTEX_ADAPTIVE_NP:
  64       /* Normal mutex.  */
  65       if (lll_mutex_trylock (mutex->__data.__lock) == 0)
  66         {
  67           /* Record the ownership.  */
  68           mutex->__data.__owner = THREAD_GETMEM (THREAD_SELF, tid);
  69           ++mutex->__data.__nusers;
  70
  71           return 0;
  72         }
  73     }
  74
  75   return EBUSY;
  76 }
  77 strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)