efffd0e96a
After exiting the try-again loop, make one more test of the lock conditions, in case it was released while a signal handler kept the thread busy past the alarm expiration.
489 lines
13 KiB
C
489 lines
13 KiB
C
/* $NetBSD: pthread_rwlock.c,v 1.11 2005/01/09 01:57:38 nathanw Exp $ */
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/*-
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* Copyright (c) 2002 The NetBSD Foundation, Inc.
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* All rights reserved.
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*
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* This code is derived from software contributed to The NetBSD Foundation
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* by Nathan J. Williams.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the NetBSD
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* Foundation, Inc. and its contributors.
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* 4. Neither the name of The NetBSD Foundation nor the names of its
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* contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
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* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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__RCSID("$NetBSD: pthread_rwlock.c,v 1.11 2005/01/09 01:57:38 nathanw Exp $");
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#include <errno.h>
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#include "pthread.h"
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#include "pthread_int.h"
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static void pthread_rwlock__callback(void *);
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__strong_alias(__libc_rwlock_init,pthread_rwlock_init)
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__strong_alias(__libc_rwlock_rdlock,pthread_rwlock_rdlock)
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__strong_alias(__libc_rwlock_wrlock,pthread_rwlock_wrlock)
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__strong_alias(__libc_rwlock_tryrdlock,pthread_rwlock_tryrdlock)
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__strong_alias(__libc_rwlock_trywrlock,pthread_rwlock_trywrlock)
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__strong_alias(__libc_rwlock_unlock,pthread_rwlock_unlock)
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__strong_alias(__libc_rwlock_destroy,pthread_rwlock_destroy)
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int
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pthread_rwlock_init(pthread_rwlock_t *rwlock,
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const pthread_rwlockattr_t *attr)
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{
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#ifdef ERRORCHECK
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if ((rwlock == NULL) ||
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(attr && (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC)))
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return EINVAL;
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#endif
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rwlock->ptr_magic = _PT_RWLOCK_MAGIC;
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pthread_lockinit(&rwlock->ptr_interlock);
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PTQ_INIT(&rwlock->ptr_rblocked);
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PTQ_INIT(&rwlock->ptr_wblocked);
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rwlock->ptr_nreaders = 0;
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rwlock->ptr_writer = NULL;
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return 0;
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}
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int
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pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
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{
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#ifdef ERRORCHECK
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if ((rwlock == NULL) ||
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(rwlock->ptr_magic != _PT_RWLOCK_MAGIC) ||
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(!PTQ_EMPTY(&rwlock->ptr_rblocked)) ||
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(!PTQ_EMPTY(&rwlock->ptr_wblocked)) ||
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(rwlock->ptr_nreaders != 0) ||
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(rwlock->ptr_writer != NULL))
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return EINVAL;
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#endif
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rwlock->ptr_magic = _PT_RWLOCK_DEAD;
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return 0;
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}
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int
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pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
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{
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pthread_t self;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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#endif
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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#ifdef ERRORCHECK
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if (rwlock->ptr_writer == self) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EDEADLK;
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}
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#endif
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/*
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* Don't get a readlock if there is a writer or if there are waiting
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* writers; i.e. prefer writers to readers. This strategy is dictated
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* by SUSv3.
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*/
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while ((rwlock->ptr_writer != NULL) ||
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(!PTQ_EMPTY(&rwlock->ptr_wblocked))) {
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PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep);
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/* Locking a rwlock is not a cancellation point; don't check */
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pthread_spinlock(self, &self->pt_statelock);
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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self->pt_sleepobj = rwlock;
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self->pt_sleepq = &rwlock->ptr_rblocked;
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self->pt_sleeplock = &rwlock->ptr_interlock;
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pthread_spinunlock(self, &self->pt_statelock);
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pthread__block(self, &rwlock->ptr_interlock);
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/* interlock is not held when we return */
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pthread_spinlock(self, &rwlock->ptr_interlock);
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}
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rwlock->ptr_nreaders++;
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return 0;
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}
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int
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pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
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{
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pthread_t self;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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#endif
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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/*
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* Don't get a readlock if there is a writer or if there are waiting
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* writers; i.e. prefer writers to readers. This strategy is dictated
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* by SUSv3.
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*/
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if ((rwlock->ptr_writer != NULL) ||
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(!PTQ_EMPTY(&rwlock->ptr_wblocked))) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EBUSY;
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}
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rwlock->ptr_nreaders++;
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return 0;
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}
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int
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pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
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{
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pthread_t self;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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#endif
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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#ifdef ERRORCHECK
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if (rwlock->ptr_writer == self) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EDEADLK;
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}
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#endif
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/*
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* Prefer writers to readers here; permit writers even if there are
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* waiting readers.
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*/
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while ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) {
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PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep);
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/* Locking a rwlock is not a cancellation point; don't check */
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pthread_spinlock(self, &self->pt_statelock);
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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self->pt_sleepobj = rwlock;
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self->pt_sleepq = &rwlock->ptr_wblocked;
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self->pt_sleeplock = &rwlock->ptr_interlock;
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pthread_spinunlock(self, &self->pt_statelock);
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pthread__block(self, &rwlock->ptr_interlock);
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/* interlock is not held when we return */
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pthread_spinlock(self, &rwlock->ptr_interlock);
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}
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rwlock->ptr_writer = self;
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return 0;
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}
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int
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pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
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{
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pthread_t self;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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#endif
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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/*
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* Prefer writers to readers here; permit writers even if there are
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* waiting readers.
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*/
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if ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EBUSY;
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}
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rwlock->ptr_writer = self;
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return 0;
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}
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struct pthread_rwlock__waitarg {
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pthread_t ptw_thread;
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pthread_rwlock_t *ptw_rwlock;
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struct pthread_queue_t *ptw_queue;
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};
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int
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pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock,
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const struct timespec *abs_timeout)
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{
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pthread_t self;
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struct pthread_rwlock__waitarg wait;
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struct pt_alarm_t alarm;
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int retval;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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if (abs_timeout == NULL)
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return EINVAL;
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#endif
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if ((abs_timeout->tv_nsec >= 1000000000) ||
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(abs_timeout->tv_nsec < 0) ||
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(abs_timeout->tv_sec < 0))
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return EINVAL;
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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#ifdef ERRORCHECK
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if (rwlock->ptr_writer == self) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EDEADLK;
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}
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#endif
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/*
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* Don't get a readlock if there is a writer or if there are waiting
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* writers; i.e. prefer writers to readers. This strategy is dictated
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* by SUSv3.
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*/
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retval = 0;
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while ((retval == 0) && ((rwlock->ptr_writer != NULL) ||
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(!PTQ_EMPTY(&rwlock->ptr_wblocked)))) {
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wait.ptw_thread = self;
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wait.ptw_rwlock = rwlock;
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wait.ptw_queue = &rwlock->ptr_rblocked;
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pthread__alarm_add(self, &alarm, abs_timeout,
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pthread_rwlock__callback, &wait);
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PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep);
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/* Locking a rwlock is not a cancellation point; don't check */
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pthread_spinlock(self, &self->pt_statelock);
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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self->pt_sleepobj = rwlock;
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self->pt_sleepq = &rwlock->ptr_rblocked;
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self->pt_sleeplock = &rwlock->ptr_interlock;
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pthread_spinunlock(self, &self->pt_statelock);
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pthread__block(self, &rwlock->ptr_interlock);
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/* interlock is not held when we return */
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pthread__alarm_del(self, &alarm);
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if (pthread__alarm_fired(&alarm))
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retval = ETIMEDOUT;
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pthread_spinlock(self, &rwlock->ptr_interlock);
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}
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/* One last chance to get the lock, in case it was released between
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the alarm firing and when this thread got rescheduled, or in case
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a signal handler kept it busy */
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if ((rwlock->ptr_writer == NULL) &&
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(PTQ_EMPTY(&rwlock->ptr_wblocked))) {
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rwlock->ptr_nreaders++;
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retval = 0;
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}
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return retval;
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}
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int
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pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock,
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const struct timespec *abs_timeout)
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{
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struct pthread_rwlock__waitarg wait;
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struct pt_alarm_t alarm;
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int retval;
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pthread_t self;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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if (abs_timeout == NULL)
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return EINVAL;
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#endif
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if ((abs_timeout->tv_nsec >= 1000000000) ||
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(abs_timeout->tv_nsec < 0) ||
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(abs_timeout->tv_sec < 0))
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return EINVAL;
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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#ifdef ERRORCHECK
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if (rwlock->ptr_writer == self) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EDEADLK;
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}
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#endif
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/*
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* Prefer writers to readers here; permit writers even if there are
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* waiting readers.
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*/
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retval = 0;
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while (retval == 0 &&
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((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL))) {
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wait.ptw_thread = self;
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wait.ptw_rwlock = rwlock;
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wait.ptw_queue = &rwlock->ptr_wblocked;
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pthread__alarm_add(self, &alarm, abs_timeout,
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pthread_rwlock__callback, &wait);
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PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep);
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/* Locking a rwlock is not a cancellation point; don't check */
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pthread_spinlock(self, &self->pt_statelock);
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self->pt_state = PT_STATE_BLOCKED_QUEUE;
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self->pt_sleepobj = rwlock;
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self->pt_sleepq = &rwlock->ptr_wblocked;
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self->pt_sleeplock = &rwlock->ptr_interlock;
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pthread_spinunlock(self, &self->pt_statelock);
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pthread__block(self, &rwlock->ptr_interlock);
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/* interlock is not held when we return */
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pthread__alarm_del(self, &alarm);
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if (pthread__alarm_fired(&alarm))
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retval = ETIMEDOUT;
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pthread_spinlock(self, &rwlock->ptr_interlock);
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}
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if ((rwlock->ptr_nreaders == 0) && (rwlock->ptr_writer == NULL)) {
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rwlock->ptr_writer = self;
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retval = 0;
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}
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return retval;
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}
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static void
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pthread_rwlock__callback(void *arg)
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{
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struct pthread_rwlock__waitarg *a;
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pthread_t self;
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a = arg;
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self = pthread__self();
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pthread_spinlock(self, &a->ptw_rwlock->ptr_interlock);
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/*
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* Don't dequeue and schedule the thread if it's already been
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* queued up by a signal or broadcast (but hasn't yet run as far
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* as pthread__alarm_del(), or we wouldn't be here, and hence can't
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* have become blocked on some *other* queue).
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*/
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if (a->ptw_thread->pt_state == PT_STATE_BLOCKED_QUEUE) {
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PTQ_REMOVE(a->ptw_queue, a->ptw_thread, pt_sleep);
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pthread__sched(self, a->ptw_thread);
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}
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pthread_spinunlock(self, &a->ptw_rwlock->ptr_interlock);
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}
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int
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pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
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{
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pthread_t self, writer;
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struct pthread_queue_t blockedq;
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#ifdef ERRORCHECK
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if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
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return EINVAL;
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#endif
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writer = NULL;
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PTQ_INIT(&blockedq);
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self = pthread__self();
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pthread_spinlock(self, &rwlock->ptr_interlock);
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if (rwlock->ptr_writer != NULL) {
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/* Releasing a write lock. */
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#ifdef ERRORCHECK
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if (rwlock->ptr_writer != self) {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EPERM;
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}
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#endif
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rwlock->ptr_writer = NULL;
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writer = PTQ_FIRST(&rwlock->ptr_wblocked);
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if (writer != NULL) {
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PTQ_REMOVE(&rwlock->ptr_wblocked, writer, pt_sleep);
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} else {
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blockedq = rwlock->ptr_rblocked;
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PTQ_INIT(&rwlock->ptr_rblocked);
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}
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} else
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#ifdef ERRORCHECK
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if (rwlock->ptr_nreaders > 0)
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#endif
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{
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/* Releasing a read lock. */
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rwlock->ptr_nreaders--;
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if (rwlock->ptr_nreaders == 0) {
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writer = PTQ_FIRST(&rwlock->ptr_wblocked);
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if (writer != NULL)
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PTQ_REMOVE(&rwlock->ptr_wblocked, writer,
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pt_sleep);
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}
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#ifdef ERRORCHECK
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} else {
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return EPERM;
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#endif
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}
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if (writer != NULL)
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pthread__sched(self, writer);
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else
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pthread__sched_sleepers(self, &blockedq);
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pthread_spinunlock(self, &rwlock->ptr_interlock);
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return 0;
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}
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int
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pthread_rwlockattr_init(pthread_rwlockattr_t *attr)
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{
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#ifdef ERRORCHECK
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if (attr == NULL)
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return EINVAL;
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#endif
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attr->ptra_magic = _PT_RWLOCKATTR_MAGIC;
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return 0;
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}
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int
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pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr)
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{
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#ifdef ERRORCHECK
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if ((attr == NULL) ||
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(attr->ptra_magic != _PT_RWLOCKATTR_MAGIC))
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return EINVAL;
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#endif
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attr->ptra_magic = _PT_RWLOCKATTR_DEAD;
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return 0;
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}
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