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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you 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 "contrib/libs/apache/arrow_next/cpp/src/arrow/util/task_group.h"
#include <atomic>
#include <condition_variable>
#include <cstdint>
#include <mutex>
#include <utility>
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/checked_cast.h"
#include "contrib/libs/apache/arrow_next/src/arrow/util/config.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/logging.h"
#include "contrib/libs/apache/arrow_next/cpp/src/arrow/util/thread_pool.h"
namespace arrow20 {
namespace internal {
namespace {
////////////////////////////////////////////////////////////////////////
// Serial TaskGroup implementation
class SerialTaskGroup : public TaskGroup {
public:
explicit SerialTaskGroup(StopToken stop_token) : stop_token_(std::move(stop_token)) {}
void AppendReal(FnOnce<Status()> task) override {
DCHECK(!finished_);
if (stop_token_.IsStopRequested()) {
status_ &= stop_token_.Poll();
return;
}
if (status_.ok()) {
status_ &= std::move(task)();
}
}
Status current_status() override { return status_; }
bool ok() const override { return status_.ok(); }
Status Finish() override {
if (!finished_) {
finished_ = true;
}
return status_;
}
Future<> FinishAsync() override { return Future<>::MakeFinished(Finish()); }
int parallelism() override { return 1; }
StopToken stop_token_;
Status status_;
bool finished_ = false;
};
////////////////////////////////////////////////////////////////////////
// Threaded TaskGroup implementation
class ThreadedTaskGroup : public TaskGroup {
public:
ThreadedTaskGroup(Executor* executor, StopToken stop_token)
: executor_(executor),
stop_token_(std::move(stop_token)),
nremaining_(0),
ok_(true),
finished_(false) {}
~ThreadedTaskGroup() override {
// Make sure all pending tasks are finished, so that dangling references
// to this don't persist.
ARROW_UNUSED(Finish());
}
void AppendReal(FnOnce<Status()> task) override {
DCHECK(!finished_);
if (stop_token_.IsStopRequested()) {
UpdateStatus(stop_token_.Poll());
return;
}
// The hot path is unlocked thanks to atomics
// Only if an error occurs is the lock taken
if (ok_.load(std::memory_order_acquire)) {
nremaining_.fetch_add(1, std::memory_order_acquire);
auto self = checked_pointer_cast<ThreadedTaskGroup>(shared_from_this());
auto callable = [self = std::move(self), task = std::move(task),
stop_token = stop_token_]() mutable {
if (self->ok_.load(std::memory_order_acquire)) {
Status st;
if (stop_token.IsStopRequested()) {
st = stop_token.Poll();
} else {
// XXX what about exceptions?
st = std::move(task)();
}
self->UpdateStatus(std::move(st));
}
self->OneTaskDone();
};
UpdateStatus(executor_->Spawn(std::move(callable)));
}
}
Status current_status() override {
std::lock_guard<std::mutex> lock(mutex_);
return status_;
}
bool ok() const override { return ok_.load(); }
Status Finish() override {
#ifdef ARROW_ENABLE_THREADING
std::unique_lock<std::mutex> lock(mutex_);
if (!finished_) {
cv_.wait(lock, [&]() { return nremaining_.load() == 0; });
// Current tasks may start other tasks, so only set this when done
finished_ = true;
}
#else
while (!finished_ && nremaining_.load() != 0) {
arrow20::internal::SerialExecutor::RunTasksOnAllExecutors();
}
finished_ = true;
#endif
return status_;
}
Future<> FinishAsync() override {
std::lock_guard<std::mutex> lock(mutex_);
if (!completion_future_.has_value()) {
if (nremaining_.load() == 0) {
completion_future_ = Future<>::MakeFinished(status_);
} else {
completion_future_ = Future<>::Make();
}
}
return *completion_future_;
}
int parallelism() override { return executor_->GetCapacity(); }
protected:
void UpdateStatus(Status&& st) {
// Must be called unlocked, only locks on error
if (ARROW_PREDICT_FALSE(!st.ok())) {
std::lock_guard<std::mutex> lock(mutex_);
ok_.store(false, std::memory_order_release);
status_ &= std::move(st);
}
}
void OneTaskDone() {
// Can be called unlocked thanks to atomics
auto nremaining = nremaining_.fetch_sub(1, std::memory_order_release) - 1;
DCHECK_GE(nremaining, 0);
if (nremaining == 0) {
// Take the lock so that ~ThreadedTaskGroup cannot destroy cv
// before cv.notify_one() has returned
std::unique_lock<std::mutex> lock(mutex_);
cv_.notify_one();
if (completion_future_.has_value()) {
// MarkFinished could be slow. We don't want to call it while we are holding
// the lock.
auto& future = *completion_future_;
const auto finished = completion_future_->is_finished();
const auto& status = status_;
// This will be redundant if the user calls Finish and not FinishAsync
if (!finished && !finished_) {
finished_ = true;
lock.unlock();
future.MarkFinished(status);
} else {
lock.unlock();
}
}
}
}
// These members are usable unlocked
Executor* executor_;
StopToken stop_token_;
std::atomic<int32_t> nremaining_;
std::atomic<bool> ok_;
std::atomic<bool> finished_;
// These members use locking
std::mutex mutex_;
std::condition_variable cv_;
Status status_;
std::optional<Future<>> completion_future_;
};
} // namespace
std::shared_ptr<TaskGroup> TaskGroup::MakeSerial(StopToken stop_token) {
return std::shared_ptr<TaskGroup>(new SerialTaskGroup{stop_token});
}
std::shared_ptr<TaskGroup> TaskGroup::MakeThreaded(Executor* thread_pool,
StopToken stop_token) {
return std::shared_ptr<TaskGroup>(new ThreadedTaskGroup{thread_pool, stop_token});
}
} // namespace internal
} // namespace arrow20
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