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93 lines
3.2 KiB
C
93 lines
3.2 KiB
C
/* Copyright (C) 2003-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>, 2003.
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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 <endian.h>
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#include <errno.h>
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#include <sysdep.h>
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#include <futex-internal.h>
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#include <pthread.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 <shlib-compat.h>
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#include "pthread_cond_common.c"
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/* We do the following steps from __pthread_cond_signal in one critical
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section: (1) signal all waiters in G1, (2) close G1 so that it can become
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the new G2 and make G2 the new G1, and (3) signal all waiters in the new
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G1. We don't need to do all these steps if there are no waiters in G1
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and/or G2. See __pthread_cond_signal for further details. */
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int
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__pthread_cond_broadcast (pthread_cond_t *cond)
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{
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LIBC_PROBE (cond_broadcast, 1, cond);
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unsigned int wrefs = atomic_load_relaxed (&cond->__data.__wrefs);
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if (wrefs >> 3 == 0)
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return 0;
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int private = __condvar_get_private (wrefs);
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__condvar_acquire_lock (cond, private);
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unsigned long long int wseq = __condvar_load_wseq_relaxed (cond);
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unsigned int g2 = wseq & 1;
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unsigned int g1 = g2 ^ 1;
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wseq >>= 1;
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bool do_futex_wake = false;
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/* Step (1): signal all waiters remaining in G1. */
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if (cond->__data.__g_size[g1] != 0)
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{
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/* Add as many signals as the remaining size of the group. */
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atomic_fetch_add_relaxed (cond->__data.__g_signals + g1,
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cond->__data.__g_size[g1] << 1);
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cond->__data.__g_size[g1] = 0;
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/* We need to wake G1 waiters before we quiesce G1 below. */
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/* TODO Only set it if there are indeed futex waiters. We could
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also try to move this out of the critical section in cases when
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G2 is empty (and we don't need to quiesce). */
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futex_wake (cond->__data.__g_signals + g1, INT_MAX, private);
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}
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/* G1 is complete. Step (2) is next unless there are no waiters in G2, in
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which case we can stop. */
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if (__condvar_quiesce_and_switch_g1 (cond, wseq, &g1, private))
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{
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/* Step (3): Send signals to all waiters in the old G2 / new G1. */
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atomic_fetch_add_relaxed (cond->__data.__g_signals + g1,
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cond->__data.__g_size[g1] << 1);
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cond->__data.__g_size[g1] = 0;
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/* TODO Only set it if there are indeed futex waiters. */
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do_futex_wake = true;
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}
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__condvar_release_lock (cond, private);
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if (do_futex_wake)
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futex_wake (cond->__data.__g_signals + g1, INT_MAX, private);
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return 0;
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}
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versioned_symbol (libpthread, __pthread_cond_broadcast, pthread_cond_broadcast,
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GLIBC_2_3_2);
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