Back to index

glibc  2.9
pthread_rwlock_tryrdlock.c
Go to the documentation of this file.
00001 /* Copyright (C) 2002, 2007 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <errno.h>
00021 #include "pthreadP.h"
00022 #include <lowlevellock.h>
00023 
00024 
00025 int
00026 __pthread_rwlock_tryrdlock (rwlock)
00027      pthread_rwlock_t *rwlock;
00028 {
00029   int result = EBUSY;
00030 
00031   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
00032 
00033   if (rwlock->__data.__writer == 0
00034       && (rwlock->__data.__nr_writers_queued == 0
00035          || PTHREAD_RWLOCK_PREFER_READER_P (rwlock)))
00036     {
00037       if (__builtin_expect (++rwlock->__data.__nr_readers == 0, 0))
00038        {
00039          --rwlock->__data.__nr_readers;
00040          result = EAGAIN;
00041        }
00042       else
00043        result = 0;
00044     }
00045 
00046   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
00047 
00048   return result;
00049 }
00050 strong_alias (__pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock)