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112 lines
2.8 KiB
C
112 lines
2.8 KiB
C
/* Try to Lock a mutex. Generic version.
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Copyright (C) 2002-2020 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 <pthread.h>
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#include <pt-internal.h>
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#define LOSE do { * (int *) 0 = 0; } while (1)
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/* Lock MUTEX, return EBUSY if we can't get it. */
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int
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__pthread_mutex_trylock (struct __pthread_mutex *mutex)
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{
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int err;
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struct __pthread *self;
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const struct __pthread_mutexattr *attr = mutex->__attr;
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if (attr == __PTHREAD_ERRORCHECK_MUTEXATTR)
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attr = &__pthread_errorcheck_mutexattr;
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if (attr == __PTHREAD_RECURSIVE_MUTEXATTR)
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attr = &__pthread_recursive_mutexattr;
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__pthread_spin_lock (&mutex->__lock);
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if (__pthread_spin_trylock (&mutex->__held) == 0)
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/* Acquired the lock. */
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{
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#if defined(ALWAYS_TRACK_MUTEX_OWNER)
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# ifndef NDEBUG
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self = _pthread_self ();
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if (self != NULL)
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/* The main thread may take a lock before the library is fully
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initialized, in particular, before the main thread has a
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TCB. */
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{
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assert (mutex->__owner == NULL);
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mutex->__owner = _pthread_self ();
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}
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# endif
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#endif
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if (attr != NULL)
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switch (attr->__mutex_type)
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{
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case PTHREAD_MUTEX_NORMAL:
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break;
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case PTHREAD_MUTEX_RECURSIVE:
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mutex->__locks = 1;
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case PTHREAD_MUTEX_ERRORCHECK:
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mutex->__owner = _pthread_self ();
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break;
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default:
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LOSE;
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}
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__pthread_spin_unlock (&mutex->__lock);
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return 0;
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}
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err = EBUSY;
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if (attr != NULL)
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{
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self = _pthread_self ();
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switch (attr->__mutex_type)
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{
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case PTHREAD_MUTEX_NORMAL:
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break;
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case PTHREAD_MUTEX_ERRORCHECK:
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/* We could check if MUTEX->OWNER is SELF, however, POSIX
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does not permit pthread_mutex_trylock to return EDEADLK
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instead of EBUSY, only pthread_mutex_lock. */
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break;
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case PTHREAD_MUTEX_RECURSIVE:
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if (mutex->__owner == self)
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{
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mutex->__locks++;
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err = 0;
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}
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break;
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default:
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LOSE;
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}
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}
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__pthread_spin_unlock (&mutex->__lock);
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return err;
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}
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strong_alias (__pthread_mutex_trylock, _pthread_mutex_trylock);
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strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock);
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