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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/*
* This file is part of the LibreOffice project.
*
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
*/
#include <comphelper/threadpool.hxx>
#include <rtl/instance.hxx>
#include <algorithm>
#include <memory>
#include <thread>
namespace comphelper {
class ThreadPool::ThreadWorker : public salhelper::Thread
{
ThreadPool *mpPool;
osl::Condition maNewWork;
bool mbWorking;
public:
explicit ThreadWorker( ThreadPool *pPool ) :
salhelper::Thread("thread-pool"),
mpPool( pPool ),
mbWorking( false )
{
}
virtual void execute() SAL_OVERRIDE
{
ThreadTask *pTask;
while ( ( pTask = waitForWork() ) )
{
pTask->doWork();
delete pTask;
}
}
ThreadTask *waitForWork()
{
ThreadTask *pRet = NULL;
osl::ResettableMutexGuard aGuard( mpPool->maGuard );
pRet = mpPool->popWork();
while( !pRet )
{
if (mbWorking)
mpPool->stopWork();
mbWorking = false;
maNewWork.reset();
if( mpPool->mbTerminate )
break;
aGuard.clear(); // unlock
maNewWork.wait();
aGuard.reset(); // lock
pRet = mpPool->popWork();
}
if (pRet)
{
if (!mbWorking)
mpPool->startWork();
mbWorking = true;
}
return pRet;
}
// Why a condition per worker thread - you may ask.
//
// Unfortunately the Windows synchronisation API that we wrap
// is horribly inadequate cf.
// http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
// The existing osl::Condition API should only ever be used
// between one producer and one consumer thread to avoid the
// lost wakeup problem.
void signalNewWork()
{
maNewWork.set();
}
};
ThreadPool::ThreadPool( sal_Int32 nWorkers ) :
mnThreadsWorking( 0 ),
mbTerminate( false )
{
for( sal_Int32 i = 0; i < nWorkers; i++ )
maWorkers.push_back( new ThreadWorker( this ) );
maTasksComplete.set();
osl::MutexGuard aGuard( maGuard );
for( size_t i = 0; i < maWorkers.size(); i++ )
maWorkers[ i ]->launch();
}
ThreadPool::~ThreadPool()
{
waitAndCleanupWorkers();
}
struct ThreadPoolStatic : public rtl::StaticWithInit< std::shared_ptr< ThreadPool >,
ThreadPoolStatic >
{
std::shared_ptr< ThreadPool > operator () () {
sal_Int32 nThreads = std::max( std::thread::hardware_concurrency(), 1U );
return std::shared_ptr< ThreadPool >( new ThreadPool( nThreads ) );
};
};
ThreadPool& ThreadPool::getSharedOptimalPool()
{
return *ThreadPoolStatic::get().get();
}
void ThreadPool::waitAndCleanupWorkers()
{
waitUntilEmpty();
osl::ResettableMutexGuard aGuard( maGuard );
mbTerminate = true;
while( !maWorkers.empty() )
{
rtl::Reference< ThreadWorker > xWorker = maWorkers.back();
maWorkers.pop_back();
assert(std::find(maWorkers.begin(), maWorkers.end(), xWorker)
== maWorkers.end());
xWorker->signalNewWork();
aGuard.clear();
{ // unlocked
xWorker->join();
xWorker.clear();
}
aGuard.reset();
}
}
void ThreadPool::pushTask( ThreadTask *pTask )
{
osl::MutexGuard aGuard( maGuard );
maTasks.insert( maTasks.begin(), pTask );
// horrible beyond belief:
for( size_t i = 0; i < maWorkers.size(); i++ )
maWorkers[ i ]->signalNewWork();
maTasksComplete.reset();
}
ThreadTask *ThreadPool::popWork()
{
if( !maTasks.empty() )
{
ThreadTask *pTask = maTasks.back();
maTasks.pop_back();
return pTask;
}
else
return NULL;
}
void ThreadPool::startWork()
{
mnThreadsWorking++;
}
void ThreadPool::stopWork()
{
assert( mnThreadsWorking > 0 );
if ( --mnThreadsWorking == 0 )
maTasksComplete.set();
}
void ThreadPool::waitUntilEmpty()
{
osl::ResettableMutexGuard aGuard( maGuard );
if( maWorkers.empty() )
{ // no threads at all -> execute the work in-line
ThreadTask *pTask;
while ( ( pTask = popWork() ) )
{
pTask->doWork();
delete pTask;
}
}
else
{
aGuard.clear();
maTasksComplete.wait();
aGuard.reset();
}
assert( maTasks.empty() );
}
} // namespace comphelper
/* vim:set shiftwidth=4 softtabstop=4 expandtab: */
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