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// locks.h
/*
* Copyright (C) 2010 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
//#include "../stdafx.h"
#pragma once
#if defined(_WIN32)
#if BOOST_VERSION >= 103500
#include <boost/thread/shared_mutex.hpp>
#undef assert
#define assert MONGO_assert
#else
#error need boost >= 1.35 for windows
#endif
#define BOOST_RWLOCK
#else
#include <pthread.h>
#endif
namespace mongo {
#ifdef BOOST_RWLOCK
class RWLock {
boost::shared_mutex _m;
public:
void lock(){
_m.lock();
}
void unlock(){
_m.unlock();
}
void lock_shared(){
_m.lock_shared();
}
void unlock_shared(){
_m.unlock_shared();
}
bool lock_shared_try( int millis ){
boost::system_time until = get_system_time();
until += boost::posix_time::milliseconds(millis);
return _m.timed_lock_shared( until );
}
bool lock_try( int millis ){
boost::system_time until = get_system_time();
until += boost::posix_time::milliseconds(millis);
return _m.timed_lock( until );
}
};
#else
class RWLock {
pthread_rwlock_t _lock;
inline void check( int x ){
if( x == 0 )
return;
log() << "pthread rwlock failed: " << x << endl;
assert( x == 0 );
}
public:
RWLock(){
check( pthread_rwlock_init( &_lock , 0 ) );
}
~RWLock(){
if ( ! __destroyingStatics ){
check( pthread_rwlock_destroy( &_lock ) );
}
}
void lock(){
check( pthread_rwlock_wrlock( &_lock ) );
}
void unlock(){
check( pthread_rwlock_unlock( &_lock ) );
}
void lock_shared(){
check( pthread_rwlock_rdlock( &_lock ) );
}
void unlock_shared(){
check( pthread_rwlock_unlock( &_lock ) );
}
bool lock_shared_try( int millis ){
return _try( millis , false );
}
bool lock_try( int millis ){
return _try( millis , true );
}
bool _try( int millis , bool write ){
while ( true ) {
int x = write ?
pthread_rwlock_trywrlock( &_lock ) :
pthread_rwlock_tryrdlock( &_lock );
if ( x <= 0 )
return true;
if ( millis-- <= 0 )
return false;
if ( x == EBUSY ){
sleepmillis(1);
continue;
}
check(x);
}
return false;
}
};
#endif
struct rwlock {
rwlock( const RWLock& lock , bool write , bool alreadyHaveLock = false )
: _lock( (RWLock&)lock ) , _write( write ){
if ( ! alreadyHaveLock ){
if ( _write )
_lock.lock();
else
_lock.lock_shared();
}
}
~rwlock(){
if ( _write )
_lock.unlock();
else
_lock.unlock_shared();
}
RWLock& _lock;
bool _write;
};
}
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