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127 lines
3.7 KiB
C
127 lines
3.7 KiB
C
/* Copyright (C) 2003,2004,2007,2011 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, see
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<http://www.gnu.org/licenses/>. */
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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 write lock for RWLOCK or return after specfied time. */
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int
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pthread_rwlock_timedwrlock (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 alone. */
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lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
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while (1)
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{
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int err;
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/* Get the rwlock if there is no writer and no reader. */
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if (rwlock->__data.__writer == 0 && rwlock->__data.__nr_readers == 0)
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{
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/* Mark self as writer. */
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rwlock->__data.__writer = THREAD_GETMEM (THREAD_SELF, tid);
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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 (__builtin_expect (rwlock->__data.__writer
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== THREAD_GETMEM (THREAD_SELF, tid), 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
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|| abstime->tv_nsec < 0, 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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result = ETIMEDOUT;
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break;
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}
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/* Remember that we are a writer. */
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if (++rwlock->__data.__nr_writers_queued == 0)
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{
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/* Overflow on number of queued writers. */
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--rwlock->__data.__nr_writers_queued;
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result = EAGAIN;
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break;
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}
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int waitval = rwlock->__data.__writer_wakeup;
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/* Free the lock. */
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lll_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
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/* Wait for the writer or reader(s) to finish. */
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err = lll_futex_timed_wait (&rwlock->__data.__writer_wakeup,
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waitval, &rt, rwlock->__data.__shared);
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/* Get the lock. */
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lll_lock (rwlock->__data.__lock, rwlock->__data.__shared);
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/* To start over again, remove the thread from the writer list. */
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--rwlock->__data.__nr_writers_queued;
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/* Did the futex call time out? */
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if (err == -ETIMEDOUT)
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{
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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_unlock (rwlock->__data.__lock, rwlock->__data.__shared);
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return result;
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}
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