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#ifndef QPID_SYS_ACTIVITY_H
#define QPID_SYS_ACTIVITY_H
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.
*
*/
#include <boost/function.hpp>
namespace qpid {
namespace sys {
/**
* An activity that may be executed by multiple threads concurrently.
* An activity has 3 states:
* - active: may have active threads, new threads may enter.
* - stopping: may have active threads but no new threads may enter.
* - stopped: no active threads and no new threads may enter.
*/
class Activity {
public:
/**
* Initially active.
*@param stoppedCallback: called when all threads have stopped.
*/
Activity(boost::function<void()> stoppedCallback)
: busy(0), stopped(false), notify(stoppedCallback) {}
/** Mark the scope of an activity thread like this:
* <pre>
* {
* Activity::Scope working(activity);
* if (working) { do stuff } // Only if activity is active.
* }
* </pre>
*/
class Scope {
Activity& state;
bool entered;
public:
Scope(Activity& s) : state(s) { entered = state.enter(); }
~Scope() { if (entered) state.exit(); }
operator bool() const { return entered; }
};
friend class Scope;
// FIXME aconway 2011-09-30: fix pre-conditions with asserts, don't allow
// multiple stops/starts.
/**
* Set state to "stopped", so no new threads can enter.
* Notify function will be called when all busy threads have left.
* No-op if already stopping.
*/
void stop() {
sys::Monitor::ScopedLock l(lock);
stopped = true;
check(l);
}
/** Set the state to "started", allow threads to enter.
* If already stopping this will prevent notify function from being called.
*/
void start() {
sys::Monitor::ScopedLock l(lock);
stopped = false;
}
/** True if Activity is stopped with no */
bool isStopped() {
sys::Monitor::ScopedLock l(lock);
return stopped && busy == 0;
}
private:
// Busy thread enters scope
bool enter() {
sys::Monitor::ScopedLock l(lock);
if (!stopped) ++busy;
return !stopped;
}
// Busy thread exits scope
void exit() {
sys::Monitor::ScopedLock l(lock);
assert(busy > 0);
--busy;
check(l);
}
void check(const sys::Monitor::ScopedLock&) {
// Called with lock held.
if (stopped && busy == 0 && notify) notify();
}
uint busy;
bool stopped;
sys::Monitor lock;
boost::function< void() > notify;
};
}} // namespace qpid::sys
#endif /*!QPID_SYS_ACTIVITY_H*/
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