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/*
* Copyright (C) 2015-2017 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include <wtf/ParallelHelperPool.h>
#include <wtf/AutomaticThread.h>
#include <wtf/DataLog.h>
#include <wtf/StringPrintStream.h>
namespace WTF {
ParallelHelperClient::ParallelHelperClient(RefPtr<ParallelHelperPool>&& pool)
: m_pool(WTFMove(pool))
{
LockHolder locker(*m_pool->m_lock);
RELEASE_ASSERT(!m_pool->m_isDying);
m_pool->m_clients.append(this);
}
ParallelHelperClient::~ParallelHelperClient()
{
LockHolder locker(*m_pool->m_lock);
finish(locker);
for (size_t i = 0; i < m_pool->m_clients.size(); ++i) {
if (m_pool->m_clients[i] == this) {
m_pool->m_clients[i] = m_pool->m_clients.last();
m_pool->m_clients.removeLast();
break;
}
}
}
void ParallelHelperClient::setTask(RefPtr<SharedTask<void ()>>&& task)
{
LockHolder locker(*m_pool->m_lock);
RELEASE_ASSERT(!m_task);
m_task = WTFMove(task);
m_pool->didMakeWorkAvailable(locker);
}
void ParallelHelperClient::finish()
{
LockHolder locker(*m_pool->m_lock);
finish(locker);
}
void ParallelHelperClient::doSomeHelping()
{
RefPtr<SharedTask<void ()>> task;
{
LockHolder locker(*m_pool->m_lock);
task = claimTask(locker);
if (!task)
return;
}
runTask(task);
}
void ParallelHelperClient::runTaskInParallel(RefPtr<SharedTask<void ()>>&& task)
{
setTask(WTFMove(task));
doSomeHelping();
finish();
}
void ParallelHelperClient::finish(const AbstractLocker&)
{
m_task = nullptr;
while (m_numActive)
m_pool->m_workCompleteCondition.wait(*m_pool->m_lock);
}
RefPtr<SharedTask<void ()>> ParallelHelperClient::claimTask(const AbstractLocker&)
{
if (!m_task)
return nullptr;
m_numActive++;
return m_task;
}
void ParallelHelperClient::runTask(const RefPtr<SharedTask<void ()>>& task)
{
RELEASE_ASSERT(m_numActive);
RELEASE_ASSERT(task);
task->run();
{
LockHolder locker(*m_pool->m_lock);
RELEASE_ASSERT(m_numActive);
// No new task could have been installed, since we were still active.
RELEASE_ASSERT(!m_task || m_task == task);
m_task = nullptr;
m_numActive--;
if (!m_numActive)
m_pool->m_workCompleteCondition.notifyAll();
}
}
ParallelHelperPool::ParallelHelperPool(CString&& threadName)
: m_lock(Box<Lock>::create())
, m_workAvailableCondition(AutomaticThreadCondition::create())
, m_threadName(WTFMove(threadName))
{
}
ParallelHelperPool::~ParallelHelperPool()
{
RELEASE_ASSERT(m_clients.isEmpty());
{
LockHolder locker(*m_lock);
m_isDying = true;
m_workAvailableCondition->notifyAll(locker);
}
for (RefPtr<AutomaticThread>& thread : m_threads)
thread->join();
}
void ParallelHelperPool::ensureThreads(unsigned numThreads)
{
LockHolder locker(*m_lock);
if (numThreads < m_numThreads)
return;
m_numThreads = numThreads;
if (getClientWithTask(locker))
didMakeWorkAvailable(locker);
}
void ParallelHelperPool::doSomeHelping()
{
ParallelHelperClient* client;
RefPtr<SharedTask<void ()>> task;
{
LockHolder locker(*m_lock);
client = getClientWithTask(locker);
if (!client)
return;
task = client->claimTask(locker);
}
client->runTask(task);
}
class ParallelHelperPool::Thread : public AutomaticThread {
public:
Thread(const AbstractLocker& locker, ParallelHelperPool& pool)
: AutomaticThread(locker, pool.m_lock, pool.m_workAvailableCondition.copyRef())
, m_pool(pool)
{
}
const char* name() const override
{
return m_pool.m_threadName.data();
}
protected:
PollResult poll(const AbstractLocker& locker) override
{
if (m_pool.m_isDying)
return PollResult::Stop;
m_client = m_pool.getClientWithTask(locker);
if (m_client) {
m_task = m_client->claimTask(locker);
return PollResult::Work;
}
return PollResult::Wait;
}
WorkResult work() override
{
m_client->runTask(m_task);
m_client = nullptr;
m_task = nullptr;
return WorkResult::Continue;
}
private:
ParallelHelperPool& m_pool;
ParallelHelperClient* m_client { nullptr };
RefPtr<SharedTask<void ()>> m_task;
};
void ParallelHelperPool::didMakeWorkAvailable(const AbstractLocker& locker)
{
while (m_numThreads > m_threads.size())
m_threads.append(adoptRef(new Thread(locker, *this)));
m_workAvailableCondition->notifyAll(locker);
}
bool ParallelHelperPool::hasClientWithTask(const AbstractLocker& locker)
{
return !!getClientWithTask(locker);
}
ParallelHelperClient* ParallelHelperPool::getClientWithTask(const AbstractLocker&)
{
// We load-balance by being random.
unsigned startIndex = m_random.getUint32(m_clients.size());
for (unsigned index = startIndex; index < m_clients.size(); ++index) {
ParallelHelperClient* client = m_clients[index];
if (client->m_task)
return client;
}
for (unsigned index = 0; index < startIndex; ++index) {
ParallelHelperClient* client = m_clients[index];
if (client->m_task)
return client;
}
return nullptr;
}
} // namespace WTF