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// @file rwlockimpl.h
/**
* Copyright (C) 2012 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/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include "mutex.h"
#if defined(NTDDI_VERSION) && defined(NTDDI_WIN7) && (NTDDI_VERSION >= NTDDI_WIN7)
// Windows slimreaderwriter version. Newer windows versions only. Under contention this is slower
// than boost::shared_mutex, but see https://jira.mongodb.org/browse/SERVER-2327 for why it cannot
// be used.
namespace mongo {
unsigned long long curTimeMicros64();
class RWLockBase {
MONGO_DISALLOW_COPYING(RWLockBase);
friend class SimpleRWLock;
SRWLOCK _lock;
protected:
RWLockBase() {
InitializeSRWLock(&_lock);
}
~RWLockBase() {
// no special action needed to destroy a SRWLOCK
}
void lock() {
AcquireSRWLockExclusive(&_lock);
}
void unlock() {
ReleaseSRWLockExclusive(&_lock);
}
void lock_shared() {
AcquireSRWLockShared(&_lock);
}
void unlock_shared() {
ReleaseSRWLockShared(&_lock);
}
bool lock_shared_try(int millis) {
if (TryAcquireSRWLockShared(&_lock))
return true;
if (millis == 0)
return false;
unsigned long long end = curTimeMicros64() + millis * 1000;
while (1) {
Sleep(1);
if (TryAcquireSRWLockShared(&_lock))
return true;
if (curTimeMicros64() >= end)
break;
}
return false;
}
bool lock_try(int millis = 0) {
if (TryAcquireSRWLockExclusive(
&_lock)) // quick check to optimistically avoid calling curTimeMicros64
return true;
if (millis == 0)
return false;
unsigned long long end = curTimeMicros64() + millis * 1000;
do {
Sleep(1);
if (TryAcquireSRWLockExclusive(&_lock))
return true;
} while (curTimeMicros64() < end);
return false;
}
// no upgradable for this impl
void lockAsUpgradable() {
lock();
}
void unlockFromUpgradable() {
unlock();
}
void upgrade() {}
public:
const char* implType() const {
return "WINSRW";
}
};
}
#else
#if defined(_WIN32)
#include "shared_mutex_win.hpp"
namespace mongo {
typedef boost::modified_shared_mutex shared_mutex;
}
#else
#include <boost/thread/shared_mutex.hpp>
namespace mongo {
using boost::shared_mutex;
}
#endif
namespace mongo {
class RWLockBase {
MONGO_DISALLOW_COPYING(RWLockBase);
friend class SimpleRWLock;
shared_mutex _m;
protected:
RWLockBase() = default;
void lock() {
_m.lock();
}
void unlock() {
_m.unlock();
}
void lockAsUpgradable() {
_m.lock_upgrade();
}
void unlockFromUpgradable() { // upgradable -> unlocked
_m.unlock_upgrade();
}
void upgrade() { // upgradable -> exclusive lock
_m.unlock_upgrade_and_lock();
}
void lock_shared() {
_m.lock_shared();
}
void unlock_shared() {
_m.unlock_shared();
}
bool lock_shared_try(int millis) {
return _m.timed_lock_shared(boost::posix_time::milliseconds(millis));
}
bool lock_try(int millis = 0) {
return _m.timed_lock(boost::posix_time::milliseconds(millis));
}
public:
const char* implType() const {
return "boost";
}
};
}
#endif
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