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8ba6ad703c
900778283a ("htl: make pthread_spin_lock really spin") made
pthread_spin_lock really spin and not block, but the current users of
__pthread_spin_lock were assuming that it blocks, i.e. they use it as a
lightweight mutex fitting in just one int.
__pthread_spin_wait provides that support back.
69 lines
1.7 KiB
C
69 lines
1.7 KiB
C
/* Post a semaphore. Generic version.
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Copyright (C) 2005-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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<https://www.gnu.org/licenses/>. */
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#include <semaphore.h>
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#include <assert.h>
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#include <pt-internal.h>
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int
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__sem_post (sem_t *sem)
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{
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struct __pthread *wakeup;
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__pthread_spin_wait (&sem->__lock);
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if (sem->__value > 0)
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/* Do a quick up. */
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{
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if (sem->__value == SEM_VALUE_MAX)
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{
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__pthread_spin_unlock (&sem->__lock);
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errno = EOVERFLOW;
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return -1;
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}
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assert (sem->__queue == NULL);
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sem->__value++;
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__pthread_spin_unlock (&sem->__lock);
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return 0;
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}
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if (sem->__queue == NULL)
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/* No one waiting. */
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{
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sem->__value = 1;
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__pthread_spin_unlock (&sem->__lock);
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return 0;
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}
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/* Wake someone up. */
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/* First dequeue someone. */
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wakeup = sem->__queue;
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__pthread_dequeue (wakeup);
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/* Then drop the lock and transfer control. */
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__pthread_spin_unlock (&sem->__lock);
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__pthread_wakeup (wakeup);
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return 0;
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}
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strong_alias (__sem_post, sem_post);
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