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/* threadpool.cpp
*/
/* Copyright 2009 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.
*/
#include "pch.h"
#include "thread_pool.h"
#include "mvar.h"
namespace mongo {
namespace threadpool {
// Worker thread
class Worker : boost::noncopyable {
public:
explicit Worker(ThreadPool& owner)
: _owner(owner)
, _is_done(true)
, _thread(boost::bind(&Worker::loop, this))
{}
// destructor will block until current operation is completed
// Acts as a "join" on this thread
~Worker() {
_task.put(Task());
_thread.join();
}
void set_task(Task& func) {
assert(!func.empty());
assert(_is_done);
_is_done = false;
_task.put(func);
}
private:
ThreadPool& _owner;
MVar<Task> _task;
bool _is_done; // only used for error detection
boost::thread _thread;
void loop() {
while (true) {
Task task = _task.take();
if (task.empty())
break; // ends the thread
try {
task();
}
catch (std::exception e) {
log() << "Unhandled exception in worker thread: " << e.what() << endl;;
}
catch (...) {
log() << "Unhandled non-exception in worker thread" << endl;
}
_is_done = true;
_owner.task_done(this);
}
}
};
ThreadPool::ThreadPool(int nThreads)
: _mutex("ThreadPool"), _tasksRemaining(0)
, _nThreads(nThreads) {
scoped_lock lock(_mutex);
while (nThreads-- > 0) {
Worker* worker = new Worker(*this);
_freeWorkers.push_front(worker);
}
}
ThreadPool::~ThreadPool() {
join();
assert(_tasks.empty());
// O(n) but n should be small
assert(_freeWorkers.size() == (unsigned)_nThreads);
while(!_freeWorkers.empty()) {
delete _freeWorkers.front();
_freeWorkers.pop_front();
}
}
void ThreadPool::join() {
scoped_lock lock(_mutex);
while(_tasksRemaining) {
_condition.wait(lock.boost());
}
}
void ThreadPool::schedule(Task task) {
scoped_lock lock(_mutex);
_tasksRemaining++;
if (!_freeWorkers.empty()) {
_freeWorkers.front()->set_task(task);
_freeWorkers.pop_front();
}
else {
_tasks.push_back(task);
}
}
// should only be called by a worker from the worker thread
void ThreadPool::task_done(Worker* worker) {
scoped_lock lock(_mutex);
if (!_tasks.empty()) {
worker->set_task(_tasks.front());
_tasks.pop_front();
}
else {
_freeWorkers.push_front(worker);
}
_tasksRemaining--;
if(_tasksRemaining == 0)
_condition.notify_all();
}
} //namespace threadpool
} //namespace mongo
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