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/* sem_wait -- wait on a semaphore. Generic futex-using version.
Copyright (C) 2003, 2007 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Paul Mackerras <paulus@au.ibm.com>, 2003.
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, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <internaltypes.h>
#include <semaphore.h>
#include <pthreadP.h>
void
attribute_hidden
__sem_wait_cleanup (void *arg)
{
struct new_sem *isem = (struct new_sem *) arg;
atomic_decrement (&isem->nwaiters);
}
int
sem_wait (sem_t *sem)
{
struct new_sem *isem = (struct new_sem *) sem;
int err;
if (atomic_decrement_if_positive (&isem->value) > 0)
return 0;
atomic_increment (&isem->nwaiters);
pthread_cleanup_push (__sem_wait_cleanup, isem);
while (1)
{
/* Enable asynchronous cancellation. Required by the standard. */
int oldtype = __pthread_enable_asynccancel ();
err = lll_futex_wait (&isem->value, 0,
isem->private ^ FUTEX_PRIVATE_FLAG);
/* Disable asynchronous cancellation. */
__pthread_disable_asynccancel (oldtype);
if (err != 0 && err != -EWOULDBLOCK)
{
__set_errno (-err);
err = -1;
break;
}
if (atomic_decrement_if_positive (&isem->value) > 0)
{
err = 0;
break;
}
}
pthread_cleanup_pop (0);
atomic_decrement (&isem->nwaiters);
return err;
}
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