1 /* Copyright 2019 The TensorFlow Authors. All Rights Reserved.
2
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9 Unless required by applicable law or agreed to in writing, software
10 distributed under the License is distributed on an "AS IS" BASIS,
11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 See the License for the specific language governing permissions and
13 limitations under the License.
14 ==============================================================================*/
15
16 #include "tensorflow/core/kernels/data/unbounded_thread_pool.h"
17
18 #include "absl/memory/memory.h"
19 #include "tensorflow/core/framework/dataset.h"
20 #include "tensorflow/core/lib/core/notification.h"
21 #include "tensorflow/core/platform/env.h"
22 #include "tensorflow/core/platform/resource.h"
23 #include "tensorflow/core/platform/unbounded_work_queue.h"
24
25 namespace tensorflow {
26 namespace data {
27
28 // A logical implementation of the `tensorflow::Thread` interface that uses
29 // physical threads in an `UnboundedThreadPool` to perform the work.
30 //
31 // NOTE: This object represents a logical thread of control that may be mapped
32 // onto the same physical thread as other work items that are submitted to the
33 // same `UnboundedThreadPool`.
34 class UnboundedThreadPool::LogicalThreadWrapper : public Thread {
35 public:
LogicalThreadWrapper(std::shared_ptr<Notification> done)36 explicit LogicalThreadWrapper(std::shared_ptr<Notification> done)
37 : done_(std::move(done)) {}
38
~LogicalThreadWrapper()39 ~LogicalThreadWrapper() override {
40 // NOTE: The `Thread` destructor is expected to "join" the created thread,
41 // but the physical thread may continue to execute after the work for this
42 // thread is complete. We simulate this by waiting on a notification that
43 // the thread's work function will notify when it is complete.
44 done_->WaitForNotification();
45 }
46
47 private:
48 std::shared_ptr<Notification> done_;
49 };
50
51 // A lightweight wrapper for creating logical threads in a `UnboundedThreadPool`
52 // that can be shared (e.g.) in an `IteratorContext`.
53 class UnboundedThreadPool::LogicalThreadFactory : public ThreadFactory {
54 public:
LogicalThreadFactory(UnboundedThreadPool * pool)55 explicit LogicalThreadFactory(UnboundedThreadPool* pool) : pool_(pool) {}
56
StartThread(const string & name,std::function<void ()> fn)57 std::unique_ptr<Thread> StartThread(const string& name,
58 std::function<void()> fn) override {
59 auto done = std::make_shared<Notification>();
60 pool_->ScheduleOnWorkQueue(std::move(fn), done);
61 return absl::make_unique<LogicalThreadWrapper>(std::move(done));
62 }
63
64 private:
65 UnboundedThreadPool* const pool_; // Not owned.
66 };
67
get_thread_factory()68 std::shared_ptr<ThreadFactory> UnboundedThreadPool::get_thread_factory() {
69 return std::make_shared<LogicalThreadFactory>(this);
70 }
71
Schedule(std::function<void ()> fn)72 void UnboundedThreadPool::Schedule(std::function<void()> fn) {
73 auto tagged_fn = [fn = std::move(fn)]() {
74 tensorflow::ResourceTagger tag(kTFDataResourceTag, "ThreadPool");
75 fn();
76 };
77 ScheduleOnWorkQueue(std::move(tagged_fn), /*done=*/nullptr);
78 }
79
NumThreads() const80 int UnboundedThreadPool::NumThreads() const { return -1; }
81
CurrentThreadId() const82 int UnboundedThreadPool::CurrentThreadId() const { return -1; }
83
84 namespace {
WorkQueueFunc(const std::function<void ()> & fn,std::shared_ptr<Notification> done)85 void WorkQueueFunc(const std::function<void()>& fn,
86 std::shared_ptr<Notification> done) {
87 fn();
88 if (done) {
89 done->Notify();
90 }
91 }
92 } // namespace
93
ScheduleOnWorkQueue(std::function<void ()> fn,std::shared_ptr<Notification> done)94 void UnboundedThreadPool::ScheduleOnWorkQueue(
95 std::function<void()> fn, std::shared_ptr<Notification> done) {
96 unbounded_work_queue_.Schedule(
97 std::bind(&WorkQueueFunc, std::move(fn), std::move(done)));
98 }
99
100 } // namespace data
101 } // namespace tensorflow
102