From a175314c3e5827eb193872241446f2f8f5c9d33c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 4 May 2024 20:07:14 +0200 Subject: Adding upstream version 1:10.5.12. Signed-off-by: Daniel Baumann --- mysys/thr_rwlock.c | 377 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 377 insertions(+) create mode 100644 mysys/thr_rwlock.c (limited to 'mysys/thr_rwlock.c') diff --git a/mysys/thr_rwlock.c b/mysys/thr_rwlock.c new file mode 100644 index 00000000..a8711d51 --- /dev/null +++ b/mysys/thr_rwlock.c @@ -0,0 +1,377 @@ +/* Copyright (c) 2000, 2011, Oracle and/or its affiliates. All rights reserved. + + This program is free software; you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; version 2 of the License. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program; if not, write to the Free Software + Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335 USA */ + +/* Synchronization - readers / writer thread locks */ + +#include "mysys_priv.h" +#if defined(NEED_MY_RW_LOCK) +#include + +#ifdef _WIN32 + +int my_rw_init(my_rw_lock_t *rwp) +{ + InitializeSRWLock(&rwp->srwlock); + rwp->have_exclusive_srwlock = FALSE; + return 0; +} + + +int my_rw_rdlock(my_rw_lock_t *rwp) +{ + AcquireSRWLockShared(&rwp->srwlock); + return 0; +} + + +int my_rw_tryrdlock(my_rw_lock_t *rwp) +{ + if (!TryAcquireSRWLockShared(&rwp->srwlock)) + return EBUSY; + return 0; +} + + +int my_rw_wrlock(my_rw_lock_t *rwp) +{ + AcquireSRWLockExclusive(&rwp->srwlock); + rwp->have_exclusive_srwlock= TRUE; + return 0; +} + +int my_rw_trywrlock(my_rw_lock_t *rwp) +{ + if (!TryAcquireSRWLockExclusive(&rwp->srwlock)) + return EBUSY; + rwp->have_exclusive_srwlock= TRUE; + return 0; +} + + +int my_rw_unlock(my_rw_lock_t *rwp) +{ + if (rwp->have_exclusive_srwlock) + { + rwp->have_exclusive_srwlock= FALSE; + ReleaseSRWLockExclusive(&rwp->srwlock); + } + else + { + ReleaseSRWLockShared(&rwp->srwlock); + } + return 0; +} + +int my_rw_destroy(my_rw_lock_t* rwp) +{ + DBUG_ASSERT(!rwp->have_exclusive_srwlock); + return 0; +} + +#else + +/* + Source base from Sun Microsystems SPILT, simplified for MySQL use + -- Joshua Chamas + Some cleanup and additional code by Monty +*/ + +/* +* Multithreaded Demo Source +* +* Copyright (C) 1995 by Sun Microsystems, Inc. +* +* +* This file is a product of SunSoft, Inc. and is provided for +* unrestricted use provided that this legend is included on all +* media and as a part of the software program in whole or part. +* Users may copy, modify or distribute this file at will. +* +* THIS FILE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING +* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR +* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE. +* +* This file is provided with no support and without any obligation on the +* part of SunSoft, Inc. to assist in its use, correction, modification or +* enhancement. +* +* SUNSOFT AND SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT +* TO THE INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS +* FILE OR ANY PART THEREOF. +* +* IN NO EVENT WILL SUNSOFT OR SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY +* LOST REVENUE OR PROFITS OR OTHER SPECIAL, INDIRECT AND CONSEQUENTIAL +* DAMAGES, EVEN IF THEY HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH +* DAMAGES. +* +* SunSoft, Inc. +* 2550 Garcia Avenue +* Mountain View, California 94043 +*/ + +int my_rw_init(my_rw_lock_t *rwp) +{ + pthread_condattr_t cond_attr; + + pthread_mutex_init( &rwp->lock, MY_MUTEX_INIT_FAST); + pthread_condattr_init( &cond_attr ); + pthread_cond_init( &rwp->readers, &cond_attr ); + pthread_cond_init( &rwp->writers, &cond_attr ); + pthread_condattr_destroy(&cond_attr); + + rwp->state = 0; + rwp->waiters = 0; +#ifdef SAFE_MUTEX + rwp->write_thread = 0; +#endif + + return(0); +} + + +int my_rw_destroy(my_rw_lock_t *rwp) +{ + DBUG_ASSERT(rwp->state == 0); + pthread_mutex_destroy( &rwp->lock ); + pthread_cond_destroy( &rwp->readers ); + pthread_cond_destroy( &rwp->writers ); + return(0); +} + + +int my_rw_rdlock(my_rw_lock_t *rwp) +{ + pthread_mutex_lock(&rwp->lock); + + /* active or queued writers */ + while (( rwp->state < 0 ) || rwp->waiters) + pthread_cond_wait( &rwp->readers, &rwp->lock); + + rwp->state++; + pthread_mutex_unlock(&rwp->lock); + return(0); +} + +int my_rw_tryrdlock(my_rw_lock_t *rwp) +{ + int res; + pthread_mutex_lock(&rwp->lock); + if ((rwp->state < 0 ) || rwp->waiters) + res= EBUSY; /* Can't get lock */ + else + { + res=0; + rwp->state++; + } + pthread_mutex_unlock(&rwp->lock); + return(res); +} + + +int my_rw_wrlock(my_rw_lock_t *rwp) +{ + pthread_mutex_lock(&rwp->lock); + rwp->waiters++; /* another writer queued */ + + my_rw_lock_assert_not_write_owner(rwp); + + while (rwp->state) + pthread_cond_wait(&rwp->writers, &rwp->lock); + rwp->state = -1; + rwp->waiters--; +#ifdef SAFE_MUTEX + rwp->write_thread= pthread_self(); +#endif + pthread_mutex_unlock(&rwp->lock); + return(0); +} + + +int my_rw_trywrlock(my_rw_lock_t *rwp) +{ + int res; + + pthread_mutex_lock(&rwp->lock); + if (rwp->state) + res= EBUSY; /* Can't get lock */ + else + { + res=0; + rwp->state = -1; +#ifdef SAFE_MUTEX + rwp->write_thread= pthread_self(); +#endif + } + pthread_mutex_unlock(&rwp->lock); + return(res); +} + + +int my_rw_unlock(my_rw_lock_t *rwp) +{ + DBUG_PRINT("rw_unlock", + ("state: %d waiters: %d", rwp->state, rwp->waiters)); + pthread_mutex_lock(&rwp->lock); + + DBUG_ASSERT(rwp->state != 0); + + if (rwp->state == -1) /* writer releasing */ + { + my_rw_lock_assert_write_owner(rwp); + rwp->state= 0; /* mark as available */ +#ifdef SAFE_MUTEX + rwp->write_thread= 0; +#endif + + if ( rwp->waiters ) /* writers queued */ + pthread_cond_signal( &rwp->writers ); + else + pthread_cond_broadcast( &rwp->readers ); + } + else + { + if ( --rwp->state == 0 && /* no more readers */ + rwp->waiters) + pthread_cond_signal( &rwp->writers ); + } + + pthread_mutex_unlock( &rwp->lock ); + return(0); +} + +#endif /* !defined _WIN32 */ +#endif /* NEED_MY_RW_LOCK*/ + + +int rw_pr_init(rw_pr_lock_t *rwlock) +{ + pthread_mutex_init(&rwlock->lock, NULL); + pthread_cond_init(&rwlock->no_active_readers, NULL); + rwlock->active_readers= 0; + rwlock->writers_waiting_readers= 0; + rwlock->active_writer= FALSE; +#ifdef SAFE_MUTEX + rwlock->writer_thread= 0; +#endif + return 0; +} + + +int rw_pr_destroy(rw_pr_lock_t *rwlock) +{ + pthread_cond_destroy(&rwlock->no_active_readers); + pthread_mutex_destroy(&rwlock->lock); + return 0; +} + + +int rw_pr_rdlock(rw_pr_lock_t *rwlock) +{ + pthread_mutex_lock(&rwlock->lock); + /* + The fact that we were able to acquire 'lock' mutex means + that there are no active writers and we can acquire rd-lock. + Increment active readers counter to prevent requests for + wr-lock from succeeding and unlock mutex. + */ + rwlock->active_readers++; + pthread_mutex_unlock(&rwlock->lock); + return 0; +} + + +int rw_pr_wrlock(rw_pr_lock_t *rwlock) +{ + pthread_mutex_lock(&rwlock->lock); + + if (rwlock->active_readers != 0) + { + /* There are active readers. We have to wait until they are gone. */ + rwlock->writers_waiting_readers++; + + while (rwlock->active_readers != 0) + pthread_cond_wait(&rwlock->no_active_readers, &rwlock->lock); + + rwlock->writers_waiting_readers--; + } + + /* + We own 'lock' mutex so there is no active writers. + Also there are no active readers. + This means that we can grant wr-lock. + Not releasing 'lock' mutex until unlock will block + both requests for rd and wr-locks. + Set 'active_writer' flag to simplify unlock. + + Thanks to the fact wr-lock/unlock in the absence of + contention from readers is essentially mutex lock/unlock + with a few simple checks make this rwlock implementation + wr-lock optimized. + */ + rwlock->active_writer= TRUE; +#ifdef SAFE_MUTEX + rwlock->writer_thread= pthread_self(); +#endif + return 0; +} + + +int rw_pr_unlock(rw_pr_lock_t *rwlock) +{ + if (rwlock->active_writer) + { + /* We are unlocking wr-lock. */ +#ifdef SAFE_MUTEX + rwlock->writer_thread= 0; +#endif + rwlock->active_writer= FALSE; + if (rwlock->writers_waiting_readers) + { + /* + Avoid expensive cond signal in case when there is no contention + or it is wr-only. + + Note that from view point of performance it would be better to + signal on the condition variable after unlocking mutex (as it + reduces number of contex switches). + + Unfortunately this would mean that such rwlock can't be safely + used by MDL subsystem, which relies on the fact that it is OK + to destroy rwlock once it is in unlocked state. + */ + pthread_cond_signal(&rwlock->no_active_readers); + } + pthread_mutex_unlock(&rwlock->lock); + } + else + { + /* We are unlocking rd-lock. */ + pthread_mutex_lock(&rwlock->lock); + rwlock->active_readers--; + if (rwlock->active_readers == 0 && + rwlock->writers_waiting_readers) + { + /* + If we are last reader and there are waiting + writers wake them up. + */ + pthread_cond_signal(&rwlock->no_active_readers); + } + pthread_mutex_unlock(&rwlock->lock); + } + return 0; +} + + -- cgit v1.2.3