glibc/nptl/sysdeps/pthread/pthread_cond_signal.c

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/* Copyright (C) 2003 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Martin Schwidefsky <schwidefsky@de.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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>
#include <shlib-compat.h>
#include <kernel-features.h>
int
__pthread_cond_signal (cond)
pthread_cond_t *cond;
{
/* Make sure we are alone. */
lll_mutex_lock (cond->__data.__lock);
/* Are there any waiters to be woken? */
if (cond->__data.__total_seq > cond->__data.__wakeup_seq)
{
/* Yes. Mark one of them as woken. */
++cond->__data.__wakeup_seq;
/* The futex syscall operates on a 32-bit word. That is fine,
we just use the low 32 bits of the sequence counter. */
#if BYTE_ORDER == LITTLE_ENDIAN
int *futex = ((int *) (&cond->__data.__wakeup_seq));
#elif BYTE_ORDER == BIG_ENDIAN
int *futex = ((int *) (&cond->__data.__wakeup_seq)) + 1;
#else
# error "No valid byte order"
#endif
/* Wake one. */
lll_futex_wake (futex, 1);
}
/* We are done. */
lll_mutex_unlock (cond->__data.__lock);
return 0;
}
versioned_symbol (libpthread, __pthread_cond_signal, pthread_cond_signal,
GLIBC_2_3_2);