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331 lines
8 KiB
C
331 lines
8 KiB
C
/* Copyright (C) 2000 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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/* Synchronization - readers / writer thread locks */
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#include "mysys_priv.h"
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#if defined(THREAD) && !defined(HAVE_PTHREAD_RWLOCK_RDLOCK) && !defined(HAVE_RWLOCK_INIT)
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#include <errno.h>
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#ifdef _WIN32
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static BOOL have_srwlock= FALSE;
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/* Prototypes and function pointers for windows functions */
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typedef VOID (WINAPI* srw_func) (PSRWLOCK SRWLock);
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typedef BOOL (WINAPI* srw_bool_func) (PSRWLOCK SRWLock);
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static srw_func my_InitializeSRWLock;
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static srw_func my_AcquireSRWLockExclusive;
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static srw_func my_ReleaseSRWLockExclusive;
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static srw_func my_AcquireSRWLockShared;
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static srw_func my_ReleaseSRWLockShared;
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static srw_bool_func my_TryAcquireSRWLockExclusive;
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static srw_bool_func my_TryAcquireSRWLockShared;
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/**
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Check for presence of Windows slim reader writer lock function.
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Load function pointers.
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*/
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static void check_srwlock_availability(void)
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{
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HMODULE module= GetModuleHandle("kernel32");
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my_InitializeSRWLock= (srw_func) GetProcAddress(module,
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"InitializeSRWLock");
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my_AcquireSRWLockExclusive= (srw_func) GetProcAddress(module,
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"AcquireSRWLockExclusive");
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my_AcquireSRWLockShared= (srw_func) GetProcAddress(module,
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"AcquireSRWLockShared");
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my_ReleaseSRWLockExclusive= (srw_func) GetProcAddress(module,
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"ReleaseSRWLockExclusive");
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my_ReleaseSRWLockShared= (srw_func) GetProcAddress(module,
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"ReleaseSRWLockShared");
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my_TryAcquireSRWLockExclusive= (srw_bool_func) GetProcAddress(module,
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"TryAcquireSRWLockExclusive");
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my_TryAcquireSRWLockShared= (srw_bool_func) GetProcAddress(module,
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"TryAcquireSRWLockShared");
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/*
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We currently require TryAcquireSRWLockExclusive. This API is missing on
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Vista, this means SRWLock are only used starting with Win7.
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If "trylock" usage for rwlocks is eliminated from server codebase (it is used
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in a single place currently, in query cache), then SRWLock can be enabled on
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Vista too. In this case condition below needs to be changed to e.g check
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for my_InitializeSRWLock.
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*/
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if (my_TryAcquireSRWLockExclusive)
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have_srwlock= TRUE;
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}
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static int srw_init(my_rw_lock_t *rwp)
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{
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my_InitializeSRWLock(&rwp->srwlock);
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rwp->have_exclusive_srwlock = FALSE;
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return 0;
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}
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static int srw_rdlock(my_rw_lock_t *rwp)
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{
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my_AcquireSRWLockShared(&rwp->srwlock);
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return 0;
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}
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static int srw_tryrdlock(my_rw_lock_t *rwp)
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{
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if (!my_TryAcquireSRWLockShared(&rwp->srwlock))
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return EBUSY;
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return 0;
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}
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static int srw_wrlock(my_rw_lock_t *rwp)
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{
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my_AcquireSRWLockExclusive(&rwp->srwlock);
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rwp->have_exclusive_srwlock= TRUE;
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return 0;
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}
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static int srw_trywrlock(my_rw_lock_t *rwp)
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{
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if (!my_TryAcquireSRWLockExclusive(&rwp->srwlock))
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return EBUSY;
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rwp->have_exclusive_srwlock= TRUE;
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return 0;
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}
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static int srw_unlock(my_rw_lock_t *rwp)
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{
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if (rwp->have_exclusive_srwlock)
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{
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rwp->have_exclusive_srwlock= FALSE;
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my_ReleaseSRWLockExclusive(&rwp->srwlock);
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}
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else
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{
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my_ReleaseSRWLockShared(&rwp->srwlock);
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}
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return 0;
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}
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#endif /*_WIN32 */
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/*
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Source base from Sun Microsystems SPILT, simplified for MySQL use
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-- Joshua Chamas
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Some cleanup and additional code by Monty
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*/
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/*
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* Multithreaded Demo Source
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*
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* Copyright (C) 1995 by Sun Microsystems, Inc.
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*
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*
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* This file is a product of SunSoft, Inc. and is provided for
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* unrestricted use provided that this legend is included on all
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* media and as a part of the software program in whole or part.
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* Users may copy, modify or distribute this file at will.
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*
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* THIS FILE IS PROVIDED AS IS WITH NO WARRANTIES OF ANY KIND INCLUDING
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* THE WARRANTIES OF DESIGN, MERCHANTIBILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE, OR ARISING FROM A COURSE OF DEALING, USAGE OR TRADE PRACTICE.
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*
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* This file is provided with no support and without any obligation on the
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* part of SunSoft, Inc. to assist in its use, correction, modification or
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* enhancement.
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*
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* SUNSOFT AND SUN MICROSYSTEMS, INC. SHALL HAVE NO LIABILITY WITH RESPECT
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* TO THE INFRINGEMENT OF COPYRIGHTS, TRADE SECRETS OR ANY PATENTS BY THIS
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* FILE OR ANY PART THEREOF.
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*
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* IN NO EVENT WILL SUNSOFT OR SUN MICROSYSTEMS, INC. BE LIABLE FOR ANY
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* LOST REVENUE OR PROFITS OR OTHER SPECIAL, INDIRECT AND CONSEQUENTIAL
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* DAMAGES, EVEN IF THEY HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
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* DAMAGES.
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*
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* SunSoft, Inc.
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* 2550 Garcia Avenue
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* Mountain View, California 94043
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*/
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int my_rwlock_init(rw_lock_t *rwp, void *arg __attribute__((unused)))
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{
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pthread_condattr_t cond_attr;
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#ifdef _WIN32
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/*
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Once initialization is used here rather than in my_init(), in order to
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- avoid my_init() pitfalls- (undefined order in which initialization should
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run)
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- be potentially useful C++ (static constructors)
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- just to simplify the API.
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Also, the overhead is of my_pthread_once is very small.
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*/
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static my_pthread_once_t once_control= MY_PTHREAD_ONCE_INIT;
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my_pthread_once(&once_control, check_srwlock_availability);
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if (have_srwlock)
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return srw_init(rwp);
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#endif
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pthread_mutex_init( &rwp->lock, MY_MUTEX_INIT_FAST);
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pthread_condattr_init( &cond_attr );
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pthread_cond_init( &rwp->readers, &cond_attr );
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pthread_cond_init( &rwp->writers, &cond_attr );
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pthread_condattr_destroy(&cond_attr);
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rwp->state = 0;
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rwp->waiters = 0;
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return(0);
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}
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int my_rwlock_destroy(rw_lock_t *rwp)
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{
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#ifdef _WIN32
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if (have_srwlock)
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return 0; /* no destroy function */
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#endif
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pthread_mutex_destroy( &rwp->lock );
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pthread_cond_destroy( &rwp->readers );
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pthread_cond_destroy( &rwp->writers );
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return(0);
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}
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int my_rw_rdlock(rw_lock_t *rwp)
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{
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#ifdef _WIN32
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if (have_srwlock)
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return srw_rdlock(rwp);
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#endif
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pthread_mutex_lock(&rwp->lock);
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/* active or queued writers */
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while ((rwp->state < 0 ) || rwp->waiters)
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pthread_cond_wait( &rwp->readers, &rwp->lock);
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rwp->state++;
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pthread_mutex_unlock(&rwp->lock);
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return(0);
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}
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int my_rw_tryrdlock(rw_lock_t *rwp)
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{
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int res;
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#ifdef _WIN32
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if (have_srwlock)
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return srw_tryrdlock(rwp);
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#endif
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pthread_mutex_lock(&rwp->lock);
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if ((rwp->state < 0 ) || rwp->waiters)
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res= EBUSY; /* Can't get lock */
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else
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{
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res=0;
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rwp->state++;
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}
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pthread_mutex_unlock(&rwp->lock);
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return(res);
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}
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int my_rw_wrlock(rw_lock_t *rwp)
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{
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#ifdef _WIN32
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if (have_srwlock)
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return srw_wrlock(rwp);
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#endif
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pthread_mutex_lock(&rwp->lock);
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rwp->waiters++; /* another writer queued */
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while (rwp->state)
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pthread_cond_wait(&rwp->writers, &rwp->lock);
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rwp->state = -1;
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rwp->waiters--;
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pthread_mutex_unlock(&rwp->lock);
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return(0);
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}
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int my_rw_trywrlock(rw_lock_t *rwp)
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{
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int res;
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#ifdef _WIN32
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if (have_srwlock)
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return srw_trywrlock(rwp);
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#endif
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pthread_mutex_lock(&rwp->lock);
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if (rwp->state)
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res= EBUSY; /* Can't get lock */
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else
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{
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res=0;
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rwp->state = -1;
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}
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pthread_mutex_unlock(&rwp->lock);
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return(res);
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}
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int my_rw_unlock(rw_lock_t *rwp)
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{
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#ifdef _WIN32
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if (have_srwlock)
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return srw_unlock(rwp);
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#endif
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DBUG_PRINT("rw_unlock",
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("state: %d waiters: %d", rwp->state, rwp->waiters));
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pthread_mutex_lock(&rwp->lock);
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if (rwp->state == -1) /* writer releasing */
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{
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rwp->state= 0; /* mark as available */
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if ( rwp->waiters ) /* writers queued */
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pthread_cond_signal( &rwp->writers );
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else
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pthread_cond_broadcast( &rwp->readers );
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}
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else
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{
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if ( --rwp->state == 0 ) /* no more readers */
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pthread_cond_signal( &rwp->writers );
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}
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pthread_mutex_unlock( &rwp->lock );
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return(0);
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}
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#endif
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