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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.
135 lines
3.9 KiB
C
135 lines
3.9 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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/* Try to acquire read lock for RWLOCK or return after specfied time. */
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int
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pthread_rwlock_timedrdlock (rwlock, abstime)
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pthread_rwlock_t *rwlock;
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const struct timespec *abstime;
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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 (++rwlock->__data.__nr_readers == 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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/* Make sure the passed in timeout value is valid. Ideally this
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test would be executed once. But since it must not be
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performed if we would not block at all simply moving the test
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to the front is no option. Replicating all the code is
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costly while this test is not. */
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if (__builtin_expect (abstime->tv_nsec >= 1000000000, 0))
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{
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result = EINVAL;
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break;
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}
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/* Get the current time. So far we support only one clock. */
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struct timeval tv;
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(void) gettimeofday (&tv, NULL);
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/* Convert the absolute timeout value to a relative timeout. */
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struct timespec rt;
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rt.tv_sec = abstime->tv_sec - tv.tv_sec;
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rt.tv_nsec = abstime->tv_nsec - tv.tv_usec * 1000;
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if (rt.tv_nsec < 0)
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{
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rt.tv_nsec += 1000000000;
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--rt.tv_sec;
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}
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/* Did we already time out? */
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if (rt.tv_sec < 0)
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{
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/* Yep, return with an appropriate error. */
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result = ETIMEDOUT;
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break;
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}
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/* Remember that we are a reader. */
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if (++rwlock->__data.__nr_readers_queued == 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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result = lll_futex_timed_wait (&rwlock->__data.__readers_wakeup, 0, &rt);
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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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/* Did the futex call time out? */
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if (result == -ETIMEDOUT)
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{
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/* Yep, report it. */
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result = ETIMEDOUT;
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break;
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}
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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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