mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-14 09:01:07 +00:00
dc6cfdc934
It is necessary to export __pthread_cond_destroy from libc because the C11 condition variable needs it and is still left in libpthread. This is part of the libpthread removal project: <https://sourceware.org/ml/libc-alpha/2019-10/msg00080.html> Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
64 lines
2.6 KiB
C
64 lines
2.6 KiB
C
/* Copyright (C) 2002-2020 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
|
|
|
|
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
|
|
<https://www.gnu.org/licenses/>. */
|
|
|
|
#include <errno.h>
|
|
#include <shlib-compat.h>
|
|
#include "pthreadP.h"
|
|
#include <stap-probe.h>
|
|
#include <atomic.h>
|
|
#include <futex-internal.h>
|
|
|
|
#include "pthread_cond_common.c"
|
|
|
|
/* See __pthread_cond_wait for a high-level description of the algorithm.
|
|
|
|
A correct program must make sure that no waiters are blocked on the condvar
|
|
when it is destroyed, and that there are no concurrent signals or
|
|
broadcasts. To wake waiters reliably, the program must signal or
|
|
broadcast while holding the mutex or after having held the mutex. It must
|
|
also ensure that no signal or broadcast are still pending to unblock
|
|
waiters; IOW, because waiters can wake up spuriously, the program must
|
|
effectively ensure that destruction happens after the execution of those
|
|
signal or broadcast calls.
|
|
Thus, we can assume that all waiters that are still accessing the condvar
|
|
have been woken. We wait until they have confirmed to have woken up by
|
|
decrementing __wrefs. */
|
|
int
|
|
__pthread_cond_destroy (pthread_cond_t *cond)
|
|
{
|
|
LIBC_PROBE (cond_destroy, 1, cond);
|
|
|
|
/* Set the wake request flag. We could also spin, but destruction that is
|
|
concurrent with still-active waiters is probably neither common nor
|
|
performance critical. Acquire MO to synchronize with waiters confirming
|
|
that they finished. */
|
|
unsigned int wrefs = atomic_fetch_or_acquire (&cond->__data.__wrefs, 4);
|
|
int private = __condvar_get_private (wrefs);
|
|
while (wrefs >> 3 != 0)
|
|
{
|
|
futex_wait_simple (&cond->__data.__wrefs, wrefs, private);
|
|
/* See above. */
|
|
wrefs = atomic_load_acquire (&cond->__data.__wrefs);
|
|
}
|
|
/* The memory the condvar occupies can now be reused. */
|
|
return 0;
|
|
}
|
|
libc_hidden_def (__pthread_cond_destroy)
|
|
versioned_symbol (libc, __pthread_cond_destroy,
|
|
pthread_cond_destroy, GLIBC_2_3_2);
|