osb/source/core/StarWorkerPool.cpp

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#include "StarWorkerPool.hpp"
#include "StarIterator.hpp"
#include "StarMathCommon.hpp"
namespace Star {
bool WorkerPoolHandle::done() const {
MutexLocker locker(m_impl->mutex);
return m_impl->done;
}
bool WorkerPoolHandle::wait(unsigned millis) const {
MutexLocker locker(m_impl->mutex);
if (!m_impl->done && millis != 0)
m_impl->condition.wait(m_impl->mutex, millis);
if (m_impl->exception)
std::rethrow_exception(m_impl->exception);
return m_impl->done;
}
bool WorkerPoolHandle::poll() const {
return wait(0);
}
void WorkerPoolHandle::finish() const {
MutexLocker locker(m_impl->mutex);
if (!m_impl->done)
m_impl->condition.wait(m_impl->mutex);
if (m_impl->exception)
std::rethrow_exception(m_impl->exception);
return;
}
WorkerPoolHandle::Impl::Impl() : done(false) {}
WorkerPoolHandle::WorkerPoolHandle(shared_ptr<Impl> impl) : m_impl(std::move(impl)) {}
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WorkerPool::WorkerPool(String name) : m_name(std::move(name)) {}
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WorkerPool::WorkerPool(String name, unsigned threadCount) : WorkerPool(std::move(name)) {
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start(threadCount);
}
WorkerPool::~WorkerPool() {
stop();
}
WorkerPool::WorkerPool(WorkerPool&&) = default;
WorkerPool& WorkerPool::operator=(WorkerPool&&) = default;
void WorkerPool::start(unsigned threadCount) {
MutexLocker threadLock(m_threadMutex);
for (auto const& workerThread : m_workerThreads)
workerThread->shouldStop = true;
m_workCondition.broadcast();
m_workerThreads.clear();
for (size_t i = m_workerThreads.size(); i < threadCount; ++i)
m_workerThreads.append(make_unique<WorkerThread>(this));
}
void WorkerPool::stop() {
MutexLocker threadLock(m_threadMutex);
for (auto const& workerThread : m_workerThreads)
workerThread->shouldStop = true;
{
// Must hold the work lock while broadcasting to ensure that any worker
// threads that might wait without stopping actually get the signal.
MutexLocker workLock(m_workMutex);
m_workCondition.broadcast();
}
m_workerThreads.clear();
}
void WorkerPool::finish() {
// This is kind of a weird way to "wait" until all the pending work is
// finished. In order for the currently active worker threads to
// cooperatively complete the remaining work, the work lock must not be held
// the entire time (then just this thread would be the one finishing the
// work). Instead, the calling thread joins in on the action and tries to
// finish work while yielding to the other threads after each completed job.
MutexLocker workMutex(m_workMutex);
while (!m_pendingWork.empty()) {
auto firstWork = m_pendingWork.takeFirst();
workMutex.unlock();
firstWork();
Thread::yield();
workMutex.lock();
}
workMutex.unlock();
stop();
}
WorkerPoolHandle WorkerPool::addWork(function<void()> work) {
// Construct a worker pool handle and wrap the work to signal the handle when
// finished. Set the result to empty string if successful and to the content
// of the exception if an exception is thrown.
auto workerPoolHandleImpl = make_shared<WorkerPoolHandle::Impl>();
queueWork([workerPoolHandleImpl, work]() {
try {
work();
MutexLocker handleLocker(workerPoolHandleImpl->mutex);
workerPoolHandleImpl->done = true;
workerPoolHandleImpl->condition.broadcast();
} catch (...) {
MutexLocker handleLocker(workerPoolHandleImpl->mutex);
workerPoolHandleImpl->done = true;
workerPoolHandleImpl->exception = std::current_exception();
workerPoolHandleImpl->condition.broadcast();
}
});
return workerPoolHandleImpl;
}
WorkerPool::WorkerThread::WorkerThread(WorkerPool* parent)
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: Thread(strf("WorkerThread for WorkerPool '{}'", parent->m_name)),
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parent(parent),
shouldStop(false),
waiting(false) {
start();
}
WorkerPool::WorkerThread::~WorkerThread() {
join();
}
void WorkerPool::WorkerThread::run() {
MutexLocker workLock(parent->m_workMutex);
while (true) {
if (shouldStop)
break;
if (parent->m_pendingWork.empty()) {
waiting = true;
parent->m_workCondition.wait(parent->m_workMutex);
waiting = false;
}
if (!parent->m_pendingWork.empty()) {
auto work = parent->m_pendingWork.takeFirst();
workLock.unlock();
work();
workLock.lock();
}
}
}
void WorkerPool::queueWork(function<void()> work) {
MutexLocker workLock(m_workMutex);
m_pendingWork.append(std::move(work));
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m_workCondition.signal();
}
}