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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.
42 lines
1.2 KiB
C
42 lines
1.2 KiB
C
/* Lock a semaphore if it does not require blocking. 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 <errno.h>
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#include <pt-internal.h>
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int
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__sem_trywait (sem_t *sem)
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{
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__pthread_spin_wait (&sem->__lock);
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if (sem->__value > 0)
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/* Successful down. */
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{
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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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__pthread_spin_unlock (&sem->__lock);
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errno = EAGAIN;
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return -1;
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}
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strong_alias (__sem_trywait, sem_trywait);
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