1 | /* Copyright 2015 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 | #ifndef TENSORFLOW_TSL_PLATFORM_BLOCKING_COUNTER_H_ |
17 | #define TENSORFLOW_TSL_PLATFORM_BLOCKING_COUNTER_H_ |
18 | |
19 | #include <atomic> |
20 | |
21 | #include "tensorflow/tsl/platform/logging.h" |
22 | #include "tensorflow/tsl/platform/mutex.h" |
23 | |
24 | namespace tsl { |
25 | |
26 | class BlockingCounter { |
27 | public: |
28 | BlockingCounter(int initial_count) |
29 | : state_(initial_count << 1), notified_(false) { |
30 | CHECK_GE(initial_count, 0); |
31 | DCHECK_EQ((initial_count << 1) >> 1, initial_count); |
32 | } |
33 | |
34 | ~BlockingCounter() {} |
35 | |
36 | inline void DecrementCount() { |
37 | unsigned int v = state_.fetch_sub(2, std::memory_order_acq_rel) - 2; |
38 | if (v != 1) { |
39 | DCHECK_NE(((v + 2) & ~1), 0); |
40 | return; // either count has not dropped to 0, or waiter is not waiting |
41 | } |
42 | mutex_lock l(mu_); |
43 | DCHECK(!notified_); |
44 | notified_ = true; |
45 | cond_var_.notify_all(); |
46 | } |
47 | |
48 | inline void Wait() { |
49 | unsigned int v = state_.fetch_or(1, std::memory_order_acq_rel); |
50 | if ((v >> 1) == 0) return; |
51 | mutex_lock l(mu_); |
52 | while (!notified_) { |
53 | cond_var_.wait(l); |
54 | } |
55 | } |
56 | // Wait for the specified time, return false iff the count has not dropped to |
57 | // zero before the timeout expired. |
58 | inline bool WaitFor(std::chrono::milliseconds ms) { |
59 | unsigned int v = state_.fetch_or(1, std::memory_order_acq_rel); |
60 | if ((v >> 1) == 0) return true; |
61 | mutex_lock l(mu_); |
62 | while (!notified_) { |
63 | const std::cv_status status = cond_var_.wait_for(l, ms); |
64 | if (status == std::cv_status::timeout) { |
65 | return false; |
66 | } |
67 | } |
68 | return true; |
69 | } |
70 | |
71 | private: |
72 | mutex mu_; |
73 | condition_variable cond_var_; |
74 | std::atomic<int> state_; // low bit is waiter flag |
75 | bool notified_; |
76 | }; |
77 | |
78 | } // namespace tsl |
79 | |
80 | #endif // TENSORFLOW_TSL_PLATFORM_BLOCKING_COUNTER_H_ |
81 | |