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Revert "Add a C++11 ThreadPool implementation in LLVM"
This reverts commit r255589. Breaks g++ From: Mehdi Amini <mehdi.amini@apple.com> git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@255591 91177308-0d34-0410-b5e6-96231b3b80d8
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Mehdi Amini
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@ -1,113 +0,0 @@
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//===-- llvm/Support/ThreadPool.h - A ThreadPool implementation -*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file defines a crude C++11 based thread pool.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_THREAD_POOL_H
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#define LLVM_SUPPORT_THREAD_POOL_H
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#include "llvm/Support/thread.h"
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#include <condition_variable>
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#include <functional>
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#include <future>
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#include <memory>
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#include <mutex>
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#include <queue>
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#include <utility>
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namespace llvm {
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/// A ThreadPool for asynchronous parallel execution on a defined number of
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/// threads.
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///
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/// The pool keeps a vector of threads alive, waiting on a condition variable
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/// for some work to become available.
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class ThreadPool {
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public:
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#ifndef _MSC_VER
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using VoidTy = void;
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#else
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// MSVC 2013 has a bug and can't use std::packaged_task<void()>;
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// We force it to use bool(bool) instead.
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using VoidTy = bool;
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#endif
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using TaskTy = std::function<VoidTy(VoidTy)>;
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using PackagedTaskTy = std::packaged_task<VoidTy(VoidTy)>;
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/// Construct a pool with the number of core available on the system (or
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/// whatever the value returned by std::thread::hardware_concurrency() is).
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ThreadPool();
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/// Construct a pool of \p ThreadCount threads
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ThreadPool(unsigned ThreadCount);
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/// Blocking destructor: the pool will wait for all the threads to complete.
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~ThreadPool();
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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template <typename Function, typename... Args>
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inline std::shared_future<VoidTy> async(Function &&F, Args &&... ArgList) {
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auto Task =
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std::bind(std::forward<Function>(F), std::forward<Args...>(ArgList...));
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#ifndef _MSC_VER
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return asyncImpl(std::move(Task));
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#else
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return asyncImpl([Task] (VoidTy) -> VoidTy { Task(); return VoidTy(); });
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#endif
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}
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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template <typename Function>
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inline std::shared_future<VoidTy> async(Function &&F) {
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#ifndef _MSC_VER
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return asyncImpl(std::forward<Function>(F));
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#else
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return asyncImpl([F] (VoidTy) -> VoidTy { F(); return VoidTy(); });
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#endif
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}
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/// Blocking wait for all the threads to complete and the queue to be empty.
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/// It is an error to try to add new tasks while blocking on this call.
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void wait();
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private:
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/// Asynchronous submission of a task to the pool. The returned future can be
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/// used to wait for the task to finish and is *non-blocking* on destruction.
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std::shared_future<VoidTy> asyncImpl(TaskTy F);
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/// Threads in flight
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std::vector<llvm::thread> Threads;
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/// Tasks waiting for execution in the pool.
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std::queue<PackagedTaskTy> Tasks;
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/// Locking and signaling for accessing the Tasks queue.
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std::mutex QueueLock;
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std::condition_variable QueueCondition;
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/// Locking and signaling for job completion
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std::mutex CompletionLock;
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std::condition_variable CompletionCondition;
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/// Keep track of the number of thread actually busy
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std::atomic<unsigned> ActiveThreads;
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#if LLVM_ENABLE_THREADS // avoids warning for unused variable
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/// Signal for the destruction of the pool, asking thread to exit.
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bool EnableFlag;
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#endif
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};
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}
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#endif // LLVM_SUPPORT_THREAD_POOL_H
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@ -43,8 +43,6 @@ typedef std::thread thread;
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#else // !LLVM_ENABLE_THREADS
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#include <utility>
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namespace llvm {
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struct thread {
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@ -89,7 +89,6 @@ add_llvm_library(LLVMSupport
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StringRef.cpp
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SystemUtils.cpp
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TargetParser.cpp
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ThreadPool.cpp
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Timer.cpp
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ToolOutputFile.cpp
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Triple.cpp
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@ -1,146 +0,0 @@
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//==-- llvm/Support/ThreadPool.cpp - A ThreadPool implementation -*- C++ -*-==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements a crude C++11 based thread pool.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/ThreadPool.h"
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#include "llvm/Config/llvm-config.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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#if LLVM_ENABLE_THREADS
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// Default to std::thread::hardware_concurrency
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ThreadPool::ThreadPool() : ThreadPool(std::thread::hardware_concurrency()) {}
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ThreadPool::ThreadPool(unsigned ThreadCount)
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: ActiveThreads(0), EnableFlag(true) {
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// Create ThreadCount threads that will loop forever, wait on QueueCondition
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// for tasks to be queued or the Pool to be destroyed.
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Threads.reserve(ThreadCount);
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for (unsigned ThreadID = 0; ThreadID < ThreadCount; ++ThreadID) {
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Threads.emplace_back([&] {
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while (true) {
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PackagedTaskTy Task;
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{
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std::unique_lock<std::mutex> LockGuard(QueueLock);
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// Wait for tasks to be pushed in the queue
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QueueCondition.wait(LockGuard,
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[&] { return !EnableFlag || !Tasks.empty(); });
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// Exit condition
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if (!EnableFlag && Tasks.empty())
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return;
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// Yeah, we have a task, grab it and release the lock on the queue
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// We first need to signal that we are active before popping the queue
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// in order for wait() to properly detect that even if the queue is
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// empty, there is still a task in flight.
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{
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++ActiveThreads;
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std::unique_lock<std::mutex> LockGuard(CompletionLock);
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}
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Task = std::move(Tasks.front());
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Tasks.pop();
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}
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// Run the task we just grabbed
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#ifndef _MSC_VER
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Task();
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#else
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Task(/* unused */ false);
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#endif
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{
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// Adjust `ActiveThreads`, in case someone waits on ThreadPool::wait()
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std::unique_lock<std::mutex> LockGuard(CompletionLock);
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--ActiveThreads;
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}
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// Notify task completion, in case someone waits on ThreadPool::wait()
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CompletionCondition.notify_all();
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}
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});
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}
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}
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void ThreadPool::wait() {
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// Wait for all threads to complete and the queue to be empty
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std::unique_lock<std::mutex> LockGuard(CompletionLock);
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CompletionCondition.wait(LockGuard,
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[&] { return Tasks.empty() && !ActiveThreads; });
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}
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std::shared_future<ThreadPool::VoidTy> ThreadPool::asyncImpl(TaskTy Task) {
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/// Wrap the Task in a packaged_task to return a future object.
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PackagedTaskTy PackagedTask(std::move(Task));
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auto Future = PackagedTask.get_future();
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{
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// Lock the queue and push the new task
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std::unique_lock<std::mutex> LockGuard(QueueLock);
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// Don't allow enqueueing after disabling the pool
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assert(EnableFlag && "Queuing a thread during ThreadPool destruction");
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Tasks.push(std::move(PackagedTask));
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}
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QueueCondition.notify_one();
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return Future.share();
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}
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// The destructor joins all threads, waiting for completion.
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ThreadPool::~ThreadPool() {
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{
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std::unique_lock<std::mutex> LockGuard(QueueLock);
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EnableFlag = false;
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}
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QueueCondition.notify_all();
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for (auto &Worker : Threads)
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Worker.join();
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}
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#else // LLVM_ENABLE_THREADS Disabled
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ThreadPool::ThreadPool() : ThreadPool(0) {}
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// No threads are launched, issue a warning if ThreadCount is not 0
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ThreadPool::ThreadPool(unsigned ThreadCount)
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: ActiveThreads(0) {
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if (ThreadCount) {
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errs() << "Warning: request a ThreadPool with " << ThreadCount
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<< " threads, but LLVM_ENABLE_THREADS has been turned off\n";
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}
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}
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void ThreadPool::wait() {
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// Sequential implementation running the tasks
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while (!Tasks.empty()) {
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auto Task = std::move(Tasks.front());
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Tasks.pop();
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Task();
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}
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}
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std::shared_future<ThreadPool::VoidTy> ThreadPool::asyncImpl(TaskTy Task) {
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// Get a Future with launch::deferred execution using std::async
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auto Future = std::async(std::launch::deferred, std::move(Task)).share();
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// Wrap the future so that both ThreadPool::wait() can operate and the
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// returned future can be sync'ed on.
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PackagedTaskTy PackagedTask([Future]() { Future.get(); });
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Tasks.push(std::move(PackagedTask));
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return Future;
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}
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ThreadPool::~ThreadPool() {
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wait();
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}
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#endif
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@ -41,7 +41,6 @@ add_llvm_unittest(SupportTests
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SwapByteOrderTest.cpp
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TargetRegistry.cpp
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ThreadLocalTest.cpp
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ThreadPool.cpp
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TimeValueTest.cpp
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TrailingObjectsTest.cpp
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UnicodeTest.cpp
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@ -1,91 +0,0 @@
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//========- unittests/Support/ThreadPools.cpp - ThreadPools.h tests --========//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/ThreadPool.h"
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#include "llvm/ADT/STLExtras.h"
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#include "gtest/gtest.h"
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using namespace llvm;
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using namespace std::chrono;
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/// Try best to make this thread not progress faster than the main thread
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static void yield() {
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#ifdef LLVM_ENABLE_THREADS
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std::this_thread::yield();
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#endif
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std::this_thread::sleep_for(milliseconds(200));
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#ifdef LLVM_ENABLE_THREADS
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std::this_thread::yield();
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#endif
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}
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TEST(ThreadPoolTest, AsyncBarrier) {
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// test that async & barrier work together properly.
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std::atomic_int checked_in{0};
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ThreadPool Pool;
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for (size_t i = 0; i < 5; ++i) {
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Pool.async([&checked_in, i] {
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yield();
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++checked_in;
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});
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}
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ASSERT_EQ(0, checked_in);
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Pool.wait();
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ASSERT_EQ(5, checked_in);
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}
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TEST(ThreadPoolTest, Async) {
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ThreadPool Pool;
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std::atomic_int i{0};
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// sleep here just to ensure that the not-equal is correct.
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Pool.async([&i] {
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yield();
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++i;
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});
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Pool.async([&i] { ++i; });
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ASSERT_NE(2, i.load());
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Pool.wait();
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ASSERT_EQ(2, i.load());
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}
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TEST(ThreadPoolTest, GetFuture) {
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ThreadPool Pool;
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std::atomic_int i{0};
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// sleep here just to ensure that the not-equal is correct.
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Pool.async([&i] {
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yield();
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++i;
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});
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// Force the future using get()
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Pool.async([&i] { ++i; }).get();
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ASSERT_NE(2, i.load());
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Pool.wait();
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ASSERT_EQ(2, i.load());
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}
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TEST(ThreadPoolTest, PoolDestruction) {
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// Test that we are waiting on destruction
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std::atomic_int checked_in{0};
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{
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ThreadPool Pool;
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for (size_t i = 0; i < 5; ++i) {
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Pool.async([&checked_in, i] {
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yield();
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++checked_in;
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});
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}
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ASSERT_EQ(0, checked_in);
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}
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ASSERT_EQ(5, checked_in);
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}
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