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// synchronization.h
/* Copyright 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/>.
*
* 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 <boost/thread/condition.hpp>
#include "mutex.h"
namespace mongo {
/**
* Type of callback functions that can be invoked when markThreadIdle() runs.
* These functions *must not throw*.
*/
typedef void(*ThreadIdleCallback)();
/**
* Informs the registered listener that this thread believes it may go idle for an extended
* period. The caller should avoid calling markThreadIdle at a high rate, as it can both be
* moderately costly itself and in terms of distributed overhead for subsequent malloc/free
* calls.
*/
void markThreadIdle();
/**
* Allows for registering callbacks for when threads go idle and become active. This is used
* by TCMalloc to return freed memory to its central freelist at appropriate points, so it
* won't happen during critical sections while holding locks. Calling this is not thread-safe.
*/
void registerThreadIdleCallback(ThreadIdleCallback callback);
/*
* A class to establish a synchronization point between two threads. One thread is the waiter
* and one is the notifier. After the notification event, both proceed normally.
*
* This class is thread-safe.
*/
class Notification {
MONGO_DISALLOW_COPYING(Notification);
public:
Notification();
/*
* Blocks until the method 'notifyOne()' is called.
*/
void waitToBeNotified();
/*
* Notifies the waiter of '*this' that it can proceed. Can only be called once.
*/
void notifyOne();
private:
mongo::mutex _mutex; // protects state below
unsigned long long lookFor;
unsigned long long cur;
boost::condition _condition; // cond over _notified being true
};
/** establishes a synchronization point between threads. N threads are waits and one is notifier.
threadsafe.
*/
class NotifyAll {
MONGO_DISALLOW_COPYING(NotifyAll);
public:
NotifyAll();
typedef unsigned long long When;
When now();
/** awaits the next notifyAll() call by another thread. notifications that precede this
call are ignored -- we are looking for a fresh event.
*/
void waitFor(When);
/** a bit faster than waitFor( now() ) */
void awaitBeyondNow();
/** may be called multiple times. notifies all waiters */
void notifyAll(When);
/** indicates how many threads are waiting for a notify. */
unsigned nWaiting() const { return _nWaiting; }
private:
mongo::mutex _mutex;
boost::condition _condition;
When _lastDone;
When _lastReturned;
unsigned _nWaiting;
};
} // namespace mongo
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