nptl/pthread_rwlock_unlock.c

   1 /* Copyright (C) 2003, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
   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 <sysdep.h>
  22 #include <lowlevellock.h>
  23 #include <pthread.h>
  24 #include <pthreadP.h>
  25
  26 /* Unlock RWLOCK.  */
  27 int
  28 __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
  29 {
  30   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
  31   if (rwlock->__data.__writer)
  32     rwlock->__data.__writer = 0;
  33   else
  34     --rwlock->__data.__nr_readers;
  35   if (rwlock->__data.__nr_readers == 0)
  36     {
  37       if (rwlock->__data.__nr_writers_queued)
  38         {
  39           ++rwlock->__data.__writer_wakeup;
  40           lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  41           lll_futex_wake (&rwlock->__data.__writer_wakeup, 1,
  42                           rwlock->__data.__shared);
  43           return 0;
  44         }
  45       else if (rwlock->__data.__nr_readers_queued)
  46         {
  47           ++rwlock->__data.__readers_wakeup;
  48           lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  49           lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
  50                           rwlock->__data.__shared);
  51           return 0;
  52         }
  53     }
  54   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  55   return 0;
  56 }
  57
  58 weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock)
  59 strong_alias (__pthread_rwlock_unlock, __pthread_rwlock_unlock_internal)