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/* Copyright (C) 2003-2013 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, see
<http://www.gnu.org/licenses/>. */
#include <endian.h>
#include <errno.h>
#include <sysdep.h>
#include <lowlevellock.h>
#include <pthread.h>
#include <pthreadP.h>
#include <shlib-compat.h>
#include <stap-probe.h>
struct _condvar_cleanup_buffer
{
int oldtype;
pthread_cond_t *cond;
pthread_mutex_t *mutex;
unsigned int bc_seq;
};
void
__attribute__ ((visibility ("hidden")))
__condvar_cleanup (void *arg)
{
struct _condvar_cleanup_buffer *cbuffer =
(struct _condvar_cleanup_buffer *) arg;
unsigned int destroying;
int pshared = (cbuffer->cond->__data.__mutex == (void *) ~0l)
? LLL_SHARED : LLL_PRIVATE;
/* We are going to modify shared data. */
lll_lock (cbuffer->cond->__data.__lock, pshared);
if (cbuffer->bc_seq == cbuffer->cond->__data.__broadcast_seq)
{
/* This thread is not waiting anymore. Adjust the sequence counters
appropriately. We do not increment WAKEUP_SEQ if this would
bump it over the value of TOTAL_SEQ. This can happen if a thread
was woken and then canceled. */
if (cbuffer->cond->__data.__wakeup_seq
< cbuffer->cond->__data.__total_seq)
{
++cbuffer->cond->__data.__wakeup_seq;
++cbuffer->cond->__data.__futex;
}
++cbuffer->cond->__data.__woken_seq;
}
cbuffer->cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
/* If pthread_cond_destroy was called on this variable already,
notify the pthread_cond_destroy caller all waiters have left
and it can be successfully destroyed. */
destroying = 0;
if (cbuffer->cond->__data.__total_seq == -1ULL
&& cbuffer->cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
{
lll_futex_wake (&cbuffer->cond->__data.__nwaiters, 1, pshared);
destroying = 1;
}
/* We are done. */
lll_unlock (cbuffer->cond->__data.__lock, pshared);
/* Wake everybody to make sure no condvar signal gets lost. */
if (! destroying)
lll_futex_wake (&cbuffer->cond->__data.__futex, INT_MAX, pshared);
/* 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;
int pshared = (cond->__data.__mutex == (void *) ~0l)
? LLL_SHARED : LLL_PRIVATE;
LIBC_PROBE (cond_wait, 2, cond, mutex);
/* Make sure we are alone. */
lll_lock (cond->__data.__lock, pshared);
/* Now we can release the mutex. */
err = __pthread_mutex_unlock_usercnt (mutex, 0);
if (__builtin_expect (err, 0))
{
lll_unlock (cond->__data.__lock, pshared);
return err;
}
/* We have one new user of the condvar. */
++cond->__data.__total_seq;
++cond->__data.__futex;
cond->__data.__nwaiters += 1 << COND_NWAITERS_SHIFT;
/* 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;
/* Remember the broadcast counter. */
cbuffer.bc_seq = cond->__data.__broadcast_seq;
do
{
unsigned int futex_val = cond->__data.__futex;
/* Prepare to wait. Release the condvar futex. */
lll_unlock (cond->__data.__lock, pshared);
/* Enable asynchronous cancellation. Required by the standard. */
cbuffer.oldtype = __pthread_enable_asynccancel ();
/* Wait until woken by signal or broadcast. */
lll_futex_wait (&cond->__data.__futex, futex_val, pshared);
/* Disable asynchronous cancellation. */
__pthread_disable_asynccancel (cbuffer.oldtype);
/* We are going to look at shared data again, so get the lock. */
lll_lock (cond->__data.__lock, pshared);
/* If a broadcast happened, we are done. */
if (cbuffer.bc_seq != cond->__data.__broadcast_seq)
goto bc_out;
/* 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;
bc_out:
cond->__data.__nwaiters -= 1 << COND_NWAITERS_SHIFT;
/* If pthread_cond_destroy was called on this varaible already,
notify the pthread_cond_destroy caller all waiters have left
and it can be successfully destroyed. */
if (cond->__data.__total_seq == -1ULL
&& cond->__data.__nwaiters < (1 << COND_NWAITERS_SHIFT))
lll_futex_wake (&cond->__data.__nwaiters, 1, pshared);
/* We are done with the condvar. */
lll_unlock (cond->__data.__lock, pshared);
/* 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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