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Diffstat (limited to 'src/mongo/util/concurrency/synchronization.h')
-rw-r--r-- | src/mongo/util/concurrency/synchronization.h | 86 |
1 files changed, 86 insertions, 0 deletions
diff --git a/src/mongo/util/concurrency/synchronization.h b/src/mongo/util/concurrency/synchronization.h new file mode 100644 index 00000000000..f9a40cc3ab9 --- /dev/null +++ b/src/mongo/util/concurrency/synchronization.h @@ -0,0 +1,86 @@ +// synchronization.h + +/* Copyright 2010 10gen Inc. + * + * Licensed under the Apache License, Version 2.0 (the "License"); + * you may not use this file except in compliance with the License. + * You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +#pragma once + +#include <boost/thread/condition.hpp> +#include "mutex.h" + +namespace mongo { + + /* + * 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 { + public: + Notification(); + ~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 : boost::noncopyable { + 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 |