48 lines
1.5 KiB
C
48 lines
1.5 KiB
C
/*
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* Copyright (c) 2013, 2014, 2021 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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* pthread/pthread_mutex_trylock.c
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* Attempts to lock a mutex.
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*/
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#include <errno.h>
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#include <limits.h>
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#include <pthread.h>
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#include <stdbool.h>
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static const int UNLOCKED = 0;
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static const int LOCKED = 1;
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int pthread_mutex_trylock(pthread_mutex_t* mutex)
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{
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int state = UNLOCKED;
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if ( !__atomic_compare_exchange_n(&mutex->lock, &state, LOCKED, false,
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__ATOMIC_SEQ_CST, __ATOMIC_SEQ_CST) )
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{
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if ( mutex->type == PTHREAD_MUTEX_RECURSIVE &&
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(pthread_t) mutex->owner == pthread_self() )
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{
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if ( mutex->recursion == ULONG_MAX )
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return errno = EAGAIN;
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mutex->recursion++;
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return 0;
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}
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return errno = EBUSY;
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}
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mutex->owner = (unsigned long) pthread_self();
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mutex->recursion = 0;
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return 0;
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}
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