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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <sysdep.h>
  21 #include <lowlevellock.h>
  22 #include <pthread.h>
  23 #include <pthreadP.h>
  24
  25 /* Unlock RWLOCK.  */
  26 int
  27 __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
  28 {
  29   lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
  30   if (rwlock->__data.__writer)
  31     rwlock->__data.__writer = 0;
  32   else
  33     --rwlock->__data.__nr_readers;
  34   if (rwlock->__data.__nr_readers == 0)
  35     {
  36       if (rwlock->__data.__nr_writers_queued)
  37         {
  38           ++rwlock->__data.__writer_wakeup;
  39           lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  40           lll_futex_wake (&rwlock->__data.__writer_wakeup, 1,
  41                           rwlock->__data.__shared);
  42           return 0;
  43         }
  44       else if (rwlock->__data.__nr_readers_queued)
  45         {
  46           ++rwlock->__data.__readers_wakeup;
  47           lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  48           lll_futex_wake (&rwlock->__data.__readers_wakeup, INT_MAX,
  49                           rwlock->__data.__shared);
  50           return 0;
  51         }
  52     }
  53   lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
  54   return 0;
  55 }
  56
  57 weak_alias (__pthread_rwlock_unlock, pthread_rwlock_unlock)
  58 strong_alias (__pthread_rwlock_unlock, __pthread_rwlock_unlock_internal)