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63 lines
2.6 KiB
C
63 lines
2.6 KiB
C
/* Copyright (C) 2002-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <shlib-compat.h>
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#include "pthreadP.h"
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#include <stap-probe.h>
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#include <atomic.h>
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#include <futex-internal.h>
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#include "pthread_cond_common.c"
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/* See __pthread_cond_wait for a high-level description of the algorithm.
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A correct program must make sure that no waiters are blocked on the condvar
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when it is destroyed, and that there are no concurrent signals or
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broadcasts. To wake waiters reliably, the program must signal or
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broadcast while holding the mutex or after having held the mutex. It must
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also ensure that no signal or broadcast are still pending to unblock
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waiters; IOW, because waiters can wake up spuriously, the program must
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effectively ensure that destruction happens after the execution of those
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signal or broadcast calls.
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Thus, we can assume that all waiters that are still accessing the condvar
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have been woken. We wait until they have confirmed to have woken up by
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decrementing __wrefs. */
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int
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__pthread_cond_destroy (pthread_cond_t *cond)
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{
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LIBC_PROBE (cond_destroy, 1, cond);
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/* Set the wake request flag. We could also spin, but destruction that is
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concurrent with still-active waiters is probably neither common nor
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performance critical. Acquire MO to synchronize with waiters confirming
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that they finished. */
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unsigned int wrefs = atomic_fetch_or_acquire (&cond->__data.__wrefs, 4);
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int private = __condvar_get_private (wrefs);
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while (wrefs >> 3 != 0)
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{
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futex_wait_simple (&cond->__data.__wrefs, wrefs, private);
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/* See above. */
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wrefs = atomic_load_acquire (&cond->__data.__wrefs);
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}
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/* The memory the condvar occupies can now be reused. */
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return 0;
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}
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versioned_symbol (libpthread, __pthread_cond_destroy,
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pthread_cond_destroy, GLIBC_2_3_2);
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