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/*
* Copyright 2016 WebAssembly Community Group participants
*
* 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 <assert.h>
#include <iostream>
#include "threads.h"
// debugging tools
#ifdef BINARYEN_THREAD_DEBUG
static std::mutex debug;
#define DEBUG_THREAD(x) { std::lock_guard<std::mutex> lock(debug); std::cerr << "[THREAD " << std::this_thread::get_id() << "] " << x; }
#define DEBUG_POOL(x) { std::lock_guard<std::mutex> lock(debug); std::cerr << "[POOL] " << x; }
#else
#define DEBUG_THREAD(x)
#define DEBUG_POOL(x)
#endif
namespace wasm {
// Global thread information
static std::unique_ptr<ThreadPool> pool;
// Thread
Thread::Thread() {
assert(!ThreadPool::get()->isRunning());
thread = std::unique_ptr<std::thread>(new std::thread(mainLoop, this));
}
Thread::~Thread() {
assert(!ThreadPool::get()->isRunning());
{
std::lock_guard<std::mutex> lock(mutex);
// notify the thread that it can exit
done = true;
condition.notify_one();
}
thread->join();
}
void Thread::work(std::function<ThreadWorkState ()> doWork_) {
// TODO: fancy work stealing
DEBUG_THREAD("send work to thread\n");
{
std::lock_guard<std::mutex> lock(mutex);
// notify the thread that it can do some work
doWork = doWork_;
condition.notify_one();
DEBUG_THREAD("work sent\n");
}
}
void Thread::mainLoop(void *self_) {
auto* self = static_cast<Thread*>(self_);
while (1) {
DEBUG_THREAD("checking for work\n");
{
std::unique_lock<std::mutex> lock(self->mutex);
if (self->doWork) {
DEBUG_THREAD("doing work\n");
// run tasks until they are all done
while (self->doWork() == ThreadWorkState::More) {}
self->doWork = nullptr;
} else if (self->done) {
DEBUG_THREAD("done\n");
return;
}
}
ThreadPool::get()->notifyThreadIsReady();
{
std::unique_lock<std::mutex> lock(self->mutex);
if (!self->done && !self->doWork) {
DEBUG_THREAD("thread waiting\n");
self->condition.wait(lock);
}
}
}
}
// ThreadPool
void ThreadPool::initialize(size_t num) {
if (num == 1) return; // no multiple cores, don't create threads
DEBUG_POOL("initialize()\n");
std::unique_lock<std::mutex> lock(mutex);
ready.store(threads.size()); // initial state before first resetThreadsAreReady()
resetThreadsAreReady();
for (size_t i = 0; i < num; i++) {
threads.emplace_back(std::unique_ptr<Thread>(new Thread()));
}
DEBUG_POOL("initialize() waiting\n");
condition.wait(lock, [this]() { return areThreadsReady(); });
DEBUG_POOL("initialize() is done\n");
}
ThreadPool* ThreadPool::get() {
if (!pool) {
size_t num = std::max(1U, std::thread::hardware_concurrency());
if (getenv("BINARYEN_CORES")) {
num = std::stoi(getenv("BINARYEN_CORES"));
}
pool = std::unique_ptr<ThreadPool>(new ThreadPool());
pool->initialize(num);
}
return pool.get();
}
void ThreadPool::work(std::vector<std::function<ThreadWorkState ()>>& doWorkers) {
size_t num = threads.size();
// If no multiple cores, or on a side thread, do not use worker threads
if (num == 0) {
// just run sequentially
DEBUG_POOL("work() sequentially\n");
assert(doWorkers.size() > 0);
while (doWorkers[0]() == ThreadWorkState::More) {}
return;
}
// run in parallel on threads
// TODO: fancy work stealing
DEBUG_POOL("work() on threads\n");
assert(doWorkers.size() == num);
assert(!running);
running = true;
std::unique_lock<std::mutex> lock(mutex);
resetThreadsAreReady();
for (size_t i = 0; i < num; i++) {
threads[i]->work(doWorkers[i]);
}
DEBUG_POOL("main thread waiting\n");
condition.wait(lock, [this]() { return areThreadsReady(); });
DEBUG_POOL("main thread waiting\n");
running = false;
DEBUG_POOL("work() is done\n");
}
size_t ThreadPool::size() {
return std::max(size_t(1), threads.size());
}
bool ThreadPool::isRunning() {
return pool && pool->running;
}
void ThreadPool::notifyThreadIsReady() {
DEBUG_POOL("notify thread is ready\n";)
std::lock_guard<std::mutex> lock(mutex);
ready.fetch_add(1);
condition.notify_one();
}
void ThreadPool::resetThreadsAreReady() {
DEBUG_POOL("reset threads are ready\n";)
auto old = ready.exchange(0);
assert(old == threads.size());
}
bool ThreadPool::areThreadsReady() {
DEBUG_POOL("are threads ready?\n";)
return ready.load() == threads.size();
}
} // namespace wasm
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