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glibc  2.9
pthread_rwlock_unlock.c
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00001 /* Copyright (C) 2003, 2007 Free Software Foundation, Inc.
00002    This file is part of the GNU C Library.
00003    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
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 <sysdep.h>
00022 #include <lowlevellock.h>
00023 #include <pthread.h>
00024 #include <pthreadP.h>
00025 
00026 /* Unlock RWLOCK.  */
00027 int
00028 __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
00029 {
00030   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
00031   if (rwlock->__data.__writer)
00032     rwlock->__data.__writer = 0;
00033   else
00034     --rwlock->__data.__nr_readers;
00035   if (rwlock->__data.__nr_readers == 0)
00036     {
00037       if (rwlock->__data.__nr_writers_queued)
00038        {
00039          ++rwlock->__data.__writer_wakeup;
00040          lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
00041          lll_futex_wake (&rwlock->__data.__writer_wakeup, 1,
00042                        rwlock->__data.__shared);
00043          return 0;
00044        }
00045       else if (rwlock->__data.__nr_readers_queued)
00046        {
00047          ++rwlock->__data.__readers_wakeup;
00048          lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
00049          lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
00050                        rwlock->__data.__shared);
00051          return 0;
00052        }
00053     }
00054   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
00055   return 0;
00056 }
00057 
00058 weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock)
00059 strong_alias (__pthread_rwlock_unlock, __pthread_rwlock_unlock_internal)