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// @file mutex.h
/* Copyright 2009 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
#ifdef _WIN32
#include "mongo/platform/windows_basic.h"
#endif
#include "mongo/stdx/mutex.h"
#include "mongo/util/assert_util.h"
#include "mongo/util/concurrency/threadlocal.h"
namespace mongo {
// If you create a local static instance of this class, that instance will be destroyed
// before all global static objects are destroyed, so _destroyingStatics will be set
// to true before the global static variables are destroyed.
class StaticObserver {
MONGO_DISALLOW_COPYING(StaticObserver);
public:
static bool _destroyingStatics;
StaticObserver() = default;
~StaticObserver() { _destroyingStatics = true; }
};
using mutex = stdx::mutex;
/** The concept with SimpleMutex is that it is a basic lock/unlock with no
special functionality (such as try and try timeout). Thus it can be
implemented using OS-specific facilities in all environments (if desired).
On Windows, the implementation below is faster than boost mutex.
*/
#if defined(_WIN32)
class SimpleMutex {
MONGO_DISALLOW_COPYING(SimpleMutex);
public:
SimpleMutex( StringData ) { InitializeCriticalSection( &_cs ); }
~SimpleMutex() {
if ( ! StaticObserver::_destroyingStatics ) {
DeleteCriticalSection(&_cs);
}
}
void dassertLocked() const { }
void lock() { EnterCriticalSection( &_cs ); }
void unlock() { LeaveCriticalSection( &_cs ); }
class scoped_lock {
SimpleMutex& _m;
public:
scoped_lock( SimpleMutex &m ) : _m(m) { _m.lock(); }
~scoped_lock() { _m.unlock(); }
const SimpleMutex& m() const { return _m; }
};
private:
CRITICAL_SECTION _cs;
};
#else
class SimpleMutex {
MONGO_DISALLOW_COPYING(SimpleMutex);
public:
void dassertLocked() const { }
SimpleMutex(StringData name) { verify( pthread_mutex_init(&_lock,0) == 0 ); }
~SimpleMutex(){
if ( ! StaticObserver::_destroyingStatics ) {
verify( pthread_mutex_destroy(&_lock) == 0 );
}
}
void lock() { verify( pthread_mutex_lock(&_lock) == 0 ); }
void unlock() { verify( pthread_mutex_unlock(&_lock) == 0 ); }
public:
class scoped_lock {
MONGO_DISALLOW_COPYING(scoped_lock);
SimpleMutex& _m;
public:
scoped_lock( SimpleMutex &m ) : _m(m) { _m.lock(); }
~scoped_lock() { _m.unlock(); }
const SimpleMutex& m() const { return _m; }
};
private:
pthread_mutex_t _lock;
};
#endif
/** This can be used instead of boost recursive mutex. The advantage is the debug checks
* and ability to assertLocked(). This has not yet been tested for speed vs. the boost one.
*/
class RecursiveMutex {
MONGO_DISALLOW_COPYING(RecursiveMutex);
public:
RecursiveMutex(StringData name) : m(name) { }
bool isLocked() const { return n.get() > 0; }
class scoped_lock {
MONGO_DISALLOW_COPYING(scoped_lock);
RecursiveMutex& rm;
int& nLocksByMe;
public:
scoped_lock( RecursiveMutex &m ) : rm(m), nLocksByMe(rm.n.getRef()) {
if( nLocksByMe++ == 0 )
rm.m.lock();
}
~scoped_lock() {
verify( nLocksByMe > 0 );
if( --nLocksByMe == 0 ) {
rm.m.unlock();
}
}
};
private:
SimpleMutex m;
ThreadLocalValue<int> n;
};
}
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