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/* Copyright (C) 2003, 2004 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>
struct _condvar_cleanup_buffer
{
int oldtype;
pthread_cond_t *cond;
pthread_mutex_t *mutex;
};
void
__attribute__ ((visibility ("hidden")))
__condvar_cleanup (void *arg)
{
struct _condvar_cleanup_buffer *cbuffer =
(struct _condvar_cleanup_buffer *) arg;
/* We are going to modify shared data. */
lll_mutex_lock (cbuffer->cond->__data.__lock);
/* This thread is not waiting anymore. Adjust the sequence counters
appropriately. */
++cbuffer->cond->__data.__wakeup_seq;
++cbuffer->cond->__data.__woken_seq;
/* We are done. */
lll_mutex_unlock (cbuffer->cond->__data.__lock);
/* Wake everybody to make sure no condvar signal gets lost. */
#if BYTE_ORDER == LITTLE_ENDIAN
int *futex = ((int *) (&cbuffer->cond->__data.__wakeup_seq));
#elif BYTE_ORDER == BIG_ENDIAN
int *futex = ((int *) (&cbuffer->cond->__data.__wakeup_seq)) + 1;
#else
# error "No valid byte order"
#endif
lll_futex_wake (futex, INT_MAX);
/* Get the mutex before returning unless asynchronous cancellation
is in effect. */
__pthread_mutex_cond_lock (cbuffer->mutex);
}
int
__pthread_cond_wait (cond, mutex)
pthread_cond_t *cond;
pthread_mutex_t *mutex;
{
struct _pthread_cleanup_buffer buffer;
struct _condvar_cleanup_buffer cbuffer;
int err;
/* Make sure we are along. */
lll_mutex_lock (cond->__data.__lock);
/* Now we can release the mutex. */
err = __pthread_mutex_unlock_usercnt (mutex, 0);
if (__builtin_expect (err, 0))
{
lll_mutex_unlock (cond->__data.__lock);
return err;
}
/* We have one new user of the condvar. */
++cond->__data.__total_seq;
/* Remember the mutex we are using here. If there is already a
different address store this is a bad user bug. Do not store
anything for pshared condvars. */
if (cond->__data.__mutex != (void *) ~0l)
cond->__data.__mutex = mutex;
/* Prepare structure passed to cancellation handler. */
cbuffer.cond = cond;
cbuffer.mutex = mutex;
/* Before we block we enable cancellation. Therefore we have to
install a cancellation handler. */
__pthread_cleanup_push (&buffer, __condvar_cleanup, &cbuffer);
/* The current values of the wakeup counter. The "woken" counter
must exceed this value. */
unsigned long long int val;
unsigned long long int seq;
val = seq = 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
do
{
/* Prepare to wait. Release the condvar futex. */
lll_mutex_unlock (cond->__data.__lock);
/* Enable asynchronous cancellation. Required by the standard. */
cbuffer.oldtype = __pthread_enable_asynccancel ();
/* Wait until woken by signal or broadcast. Note that we
truncate the 'val' value to 32 bits. */
lll_futex_wait (futex, (unsigned int) val);
/* Disable asynchronous cancellation. */
__pthread_disable_asynccancel (cbuffer.oldtype);
/* We are going to look at shared data again, so get the lock. */
lll_mutex_lock (cond->__data.__lock);
/* Check whether we are eligible for wakeup. */
val = cond->__data.__wakeup_seq;
}
while (val == seq || cond->__data.__woken_seq == val);
/* Another thread woken up. */
++cond->__data.__woken_seq;
/* We are done with the condvar. */
lll_mutex_unlock (cond->__data.__lock);
/* The cancellation handling is back to normal, remove the handler. */
__pthread_cleanup_pop (&buffer, 0);
/* Get the mutex before returning. */
return __pthread_mutex_cond_lock (mutex);
}
versioned_symbol (libpthread, __pthread_cond_wait, pthread_cond_wait,
GLIBC_2_3_2);
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