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#include "tensorflow/core/lib/core/threadpool.h"
#include "tensorflow/core/platform/port.h"
#include "tensorflow/core/platform/logging.h"
#include "tensorflow/core/platform/tracing.h"
namespace tensorflow {
namespace thread {
struct ThreadPool::Waiter {
condition_variable cv;
bool ready;
};
ThreadPool::ThreadPool(Env* env, const string& name, int num_threads)
: ThreadPool(env, ThreadOptions(), name, num_threads) {}
ThreadPool::ThreadPool(Env* env, const ThreadOptions& thread_options,
const string& name, int num_threads)
: name_(name) {
CHECK_GE(num_threads, 1);
string name_prefix = "tf_" + name_;
for (int i = 0; i < num_threads; i++) {
threads_.push_back(env->StartThread(thread_options, name_prefix,
[this]() { WorkerLoop(); }));
}
}
ThreadPool::~ThreadPool() {
{
// Wait for all work to get done.
mutex_lock l(mu_);
// Inform every thread to exit.
for (size_t i = 0; i < threads_.size(); ++i) {
pending_.push_back({nullptr, 0});
}
// Wakeup all waiters.
for (auto w : waiters_) {
w->ready = true;
w->cv.notify_one();
}
}
// Wait for threads to finish.
for (auto t : threads_) {
delete t;
}
}
bool ThreadPool::HasPendingClosures() const {
mutex_lock l(mu_);
return pending_.size() != 0;
}
void ThreadPool::Schedule(std::function<void()> fn) {
CHECK(fn != nullptr);
uint64 id = 0;
if (port::Tracing::IsActive()) {
id = port::Tracing::UniqueId();
port::Tracing::RecordEvent(port::Tracing::EventCategory::kScheduleClosure,
id);
}
mutex_lock l(mu_);
pending_.push_back({fn, id});
if (!waiters_.empty()) {
Waiter* w = waiters_.back();
waiters_.pop_back();
w->ready = true;
w->cv.notify_one();
}
}
void ThreadPool::WorkerLoop() {
port::Tracing::RegisterCurrentThread(name_.c_str());
mutex_lock l(mu_);
Waiter w;
while (true) {
while (pending_.empty()) {
// Wait for work to be assigned to me
w.ready = false;
waiters_.push_back(&w);
while (!w.ready) {
w.cv.wait(l);
}
}
// Pick up pending work
Item item = pending_.front();
pending_.pop_front();
if (item.fn == nullptr) {
break;
}
mu_.unlock();
if (item.id != 0) {
port::Tracing::ScopedActivity region(
port::Tracing::EventCategory::kRunClosure, item.id);
item.fn();
} else {
item.fn();
}
mu_.lock();
}
}
} // namespace thread
} // namespace tensorflow
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