diff options
Diffstat (limited to 'dep/mysqllite/mysys/thr_rwlock.c')
| -rw-r--r-- | dep/mysqllite/mysys/thr_rwlock.c | 472 |
1 files changed, 0 insertions, 472 deletions
diff --git a/dep/mysqllite/mysys/thr_rwlock.c b/dep/mysqllite/mysys/thr_rwlock.c deleted file mode 100644 index bad80b43eef..00000000000 --- a/dep/mysqllite/mysys/thr_rwlock.c +++ /dev/null @@ -1,472 +0,0 @@ -/* Copyright (C) 2000 MySQL AB - - 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ - -/* Synchronization - readers / writer thread locks */ - -#include "mysys_priv.h" -#if defined(NEED_MY_RW_LOCK) -#include <errno.h> - -#ifdef _WIN32 - -static BOOL have_srwlock= FALSE; -/* Prototypes and function pointers for windows functions */ -typedef VOID (WINAPI* srw_func) (PSRWLOCK SRWLock); -typedef BOOL (WINAPI* srw_bool_func) (PSRWLOCK SRWLock); - -static srw_func my_InitializeSRWLock; -static srw_func my_AcquireSRWLockExclusive; -static srw_func my_ReleaseSRWLockExclusive; -static srw_func my_AcquireSRWLockShared; -static srw_func my_ReleaseSRWLockShared; - -static srw_bool_func my_TryAcquireSRWLockExclusive; -static srw_bool_func my_TryAcquireSRWLockShared; - -/** - Check for presence of Windows slim reader writer lock function. - Load function pointers. -*/ - -static void check_srwlock_availability(void) -{ - HMODULE module= GetModuleHandle("kernel32"); - - my_InitializeSRWLock= (srw_func) GetProcAddress(module, - "InitializeSRWLock"); - my_AcquireSRWLockExclusive= (srw_func) GetProcAddress(module, - "AcquireSRWLockExclusive"); - my_AcquireSRWLockShared= (srw_func) GetProcAddress(module, - "AcquireSRWLockShared"); - my_ReleaseSRWLockExclusive= (srw_func) GetProcAddress(module, - "ReleaseSRWLockExclusive"); - my_ReleaseSRWLockShared= (srw_func) GetProcAddress(module, - "ReleaseSRWLockShared"); - my_TryAcquireSRWLockExclusive= (srw_bool_func) GetProcAddress(module, - "TryAcquireSRWLockExclusive"); - my_TryAcquireSRWLockShared= (srw_bool_func) GetProcAddress(module, - "TryAcquireSRWLockShared"); - - /* - We currently require TryAcquireSRWLockExclusive. This API is missing on - Vista, this means SRWLock are only used starting with Win7. - - If "trylock" usage for rwlocks is eliminated from server codebase (it is used - in a single place currently, in query cache), then SRWLock can be enabled on - Vista too. In this case condition below needs to be changed to e.g check - for my_InitializeSRWLock. - */ - - if (my_TryAcquireSRWLockExclusive) - have_srwlock= TRUE; - -} - - -static int srw_init(my_rw_lock_t *rwp) -{ - my_InitializeSRWLock(&rwp->srwlock); - rwp->have_exclusive_srwlock = FALSE; - return 0; -} - - -static int srw_rdlock(my_rw_lock_t *rwp) -{ - my_AcquireSRWLockShared(&rwp->srwlock); - return 0; -} - - -static int srw_tryrdlock(my_rw_lock_t *rwp) -{ - - if (!my_TryAcquireSRWLockShared(&rwp->srwlock)) - return EBUSY; - return 0; -} - - -static int srw_wrlock(my_rw_lock_t *rwp) -{ - my_AcquireSRWLockExclusive(&rwp->srwlock); - rwp->have_exclusive_srwlock= TRUE; - return 0; -} - - -static int srw_trywrlock(my_rw_lock_t *rwp) -{ - if (!my_TryAcquireSRWLockExclusive(&rwp->srwlock)) - return EBUSY; - rwp->have_exclusive_srwlock= TRUE; - return 0; -} - - -static int srw_unlock(my_rw_lock_t *rwp) -{ - if (rwp->have_exclusive_srwlock) - { - rwp->have_exclusive_srwlock= FALSE; - my_ReleaseSRWLockExclusive(&rwp->srwlock); - } - else - { - my_ReleaseSRWLockShared(&rwp->srwlock); - } - return 0; -} - -#endif /*_WIN32 */ - -/* - 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. -* All rights reserved. -* -* 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; - -#ifdef _WIN32 - /* - Once initialization is used here rather than in my_init(), in order to - - avoid my_init() pitfalls- (undefined order in which initialization should - run) - - be potentially useful C++ (static constructors) - - just to simplify the API. - Also, the overhead is of my_pthread_once is very small. - */ - static my_pthread_once_t once_control= MY_PTHREAD_ONCE_INIT; - my_pthread_once(&once_control, check_srwlock_availability); - - if (have_srwlock) - return srw_init(rwp); -#endif - - 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) -{ -#ifdef _WIN32 - if (have_srwlock) - return 0; /* no destroy function */ -#endif - 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) -{ -#ifdef _WIN32 - if (have_srwlock) - return srw_rdlock(rwp); -#endif - - 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; - -#ifdef _WIN32 - if (have_srwlock) - return srw_tryrdlock(rwp); -#endif - - 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) -{ -#ifdef _WIN32 - if (have_srwlock) - return srw_wrlock(rwp); -#endif - - 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; - -#ifdef _WIN32 - if (have_srwlock) - return srw_trywrlock(rwp); -#endif - - 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) -{ -#ifdef _WIN32 - if (have_srwlock) - return srw_unlock(rwp); -#endif - - 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(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; -} - - |