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/* Copyright (C) 2008 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by David Bartley <dtbartle@csclub.uwaterloo.ca>, 2008.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <errno.h>
#include <pthreadP.h>
#include <synch.h>
int rw_tryrdlock (rwlock)
rwlock_t *rwlock;
{
int errval = mutex_trylock (&rwlock->mutex);
if (errval != 0)
return errval;
if ((rwlock->readers & _RWLOCK_WR_LOCK) ||
(__cond_has_waiters (&rwlock->writercv) &&
!PTHREAD_RWLOCK_PREFER_READER_P (rwlock)))
{
(void)mutex_unlock (&rwlock->mutex);
return EBUSY;
}
/* Increment readers (note that no other bits are set). */
if (rwlock->readers == _RWLOCK_RD_MAX)
{
(void)mutex_unlock (&rwlock->mutex);
return EAGAIN;
}
rwlock->readers++;
(void)mutex_unlock (&rwlock->mutex);
return 0;
}
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