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a88c926368
2003-02-05 Ulrich Drepper <drepper@redhat.com> * sysdeps/pthread/bits/libc-lock.h (__libc_once): Set control variable for non-libpthread case to the same value the pthread_once function would use.
97 lines
2.9 KiB
C
97 lines
2.9 KiB
C
/* Copyright (C) 2003 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, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <errno.h>
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#include <sysdep.h>
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#include <lowlevellock.h>
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#include <pthread.h>
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#include <pthreadP.h>
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/* Acquire read lock for RWLOCK. */
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int
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__pthread_rwlock_rdlock (rwlock)
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pthread_rwlock_t *rwlock;
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{
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int result = 0;
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/* Make sure we are along. */
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lll_mutex_lock (rwlock->__data.__lock);
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while (1)
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{
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/* Get the rwlock if there is no writer... */
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if (rwlock->__data.__writer == 0
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/* ...and if either no writer is waiting or we prefer readers. */
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&& (!rwlock->__data.__nr_writers_queued
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|| rwlock->__data.__flags == 0))
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{
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/* Increment the reader counter. Avoid overflow. */
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if (__builtin_expect (++rwlock->__data.__nr_readers == 0, 0))
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{
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/* Overflow on number of readers. */
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--rwlock->__data.__nr_readers;
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result = EAGAIN;
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}
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break;
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}
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/* Make sure we are not holding the rwlock as a writer. This is
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a deadlock situation we recognize and report. */
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if (rwlock->__data.__writer != 0
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&& __builtin_expect (rwlock->__data.__writer
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== (pthread_t) THREAD_SELF, 0))
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{
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result = EDEADLK;
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break;
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}
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/* Remember that we are a reader. */
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if (__builtin_expect (++rwlock->__data.__nr_readers_queued == 0, 0))
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{
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/* Overflow on number of queued readers. */
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--rwlock->__data.__nr_readers_queued;
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result = EAGAIN;
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break;
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}
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/* Free the lock. */
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lll_mutex_unlock (rwlock->__data.__lock);
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/* Wait for the writer to finish. */
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lll_futex_wait (&rwlock->__data.__readers_wakeup, 0);
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/* Get the lock. */
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lll_mutex_lock (rwlock->__data.__lock);
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/* To start over again, remove the thread from the reader list. */
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if (--rwlock->__data.__nr_readers_queued == 0)
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rwlock->__data.__readers_wakeup = 0;
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}
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/* We are done, free the lock. */
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lll_mutex_unlock (rwlock->__data.__lock);
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return result;
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}
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weak_alias (__pthread_rwlock_rdlock, pthread_rwlock_rdlock)
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strong_alias (__pthread_rwlock_rdlock, __pthread_rwlock_rdlock_internal)
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