/src/abseil-cpp/absl/synchronization/internal/per_thread_sem.cc
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1 | | // Copyright 2017 The Abseil Authors. |
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 | | // https://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 | | // This file is a no-op if the required LowLevelAlloc support is missing. |
16 | | #include "absl/base/internal/low_level_alloc.h" |
17 | | #ifndef ABSL_LOW_LEVEL_ALLOC_MISSING |
18 | | |
19 | | #include "absl/synchronization/internal/per_thread_sem.h" |
20 | | |
21 | | #include <atomic> |
22 | | |
23 | | #include "absl/base/attributes.h" |
24 | | #include "absl/base/internal/thread_identity.h" |
25 | | #include "absl/synchronization/internal/waiter.h" |
26 | | |
27 | | namespace absl { |
28 | | ABSL_NAMESPACE_BEGIN |
29 | | namespace synchronization_internal { |
30 | | |
31 | 0 | void PerThreadSem::SetThreadBlockedCounter(std::atomic<int> *counter) { |
32 | 0 | base_internal::ThreadIdentity *identity; |
33 | 0 | identity = GetOrCreateCurrentThreadIdentity(); |
34 | 0 | identity->blocked_count_ptr = counter; |
35 | 0 | } |
36 | | |
37 | 0 | std::atomic<int> *PerThreadSem::GetThreadBlockedCounter() { |
38 | 0 | base_internal::ThreadIdentity *identity; |
39 | 0 | identity = GetOrCreateCurrentThreadIdentity(); |
40 | 0 | return identity->blocked_count_ptr; |
41 | 0 | } |
42 | | |
43 | 0 | void PerThreadSem::Tick(base_internal::ThreadIdentity *identity) { |
44 | 0 | const int ticker = |
45 | 0 | identity->ticker.fetch_add(1, std::memory_order_relaxed) + 1; |
46 | 0 | const int wait_start = identity->wait_start.load(std::memory_order_relaxed); |
47 | 0 | const bool is_idle = identity->is_idle.load(std::memory_order_relaxed); |
48 | 0 | if (wait_start && (ticker - wait_start > Waiter::kIdlePeriods) && !is_idle) { |
49 | | // Wakeup the waiting thread since it is time for it to become idle. |
50 | 0 | ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)(identity); |
51 | 0 | } |
52 | 0 | } |
53 | | |
54 | | } // namespace synchronization_internal |
55 | | ABSL_NAMESPACE_END |
56 | | } // namespace absl |
57 | | |
58 | | extern "C" { |
59 | | |
60 | | ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemInit)( |
61 | 2 | absl::base_internal::ThreadIdentity *identity) { |
62 | 2 | new (absl::synchronization_internal::Waiter::GetWaiter(identity)) |
63 | 2 | absl::synchronization_internal::Waiter(); |
64 | 2 | } |
65 | | |
66 | | ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPost)( |
67 | 0 | absl::base_internal::ThreadIdentity *identity) { |
68 | 0 | absl::synchronization_internal::Waiter::GetWaiter(identity)->Post(); |
69 | 0 | } |
70 | | |
71 | | ABSL_ATTRIBUTE_WEAK void ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemPoke)( |
72 | 0 | absl::base_internal::ThreadIdentity *identity) { |
73 | 0 | absl::synchronization_internal::Waiter::GetWaiter(identity)->Poke(); |
74 | 0 | } |
75 | | |
76 | | ABSL_ATTRIBUTE_WEAK bool ABSL_INTERNAL_C_SYMBOL(AbslInternalPerThreadSemWait)( |
77 | 0 | absl::synchronization_internal::KernelTimeout t) { |
78 | 0 | bool timeout = false; |
79 | 0 | absl::base_internal::ThreadIdentity *identity; |
80 | 0 | identity = absl::synchronization_internal::GetOrCreateCurrentThreadIdentity(); |
81 | | |
82 | | // Ensure wait_start != 0. |
83 | 0 | int ticker = identity->ticker.load(std::memory_order_relaxed); |
84 | 0 | identity->wait_start.store(ticker ? ticker : 1, std::memory_order_relaxed); |
85 | 0 | identity->is_idle.store(false, std::memory_order_relaxed); |
86 | |
|
87 | 0 | if (identity->blocked_count_ptr != nullptr) { |
88 | | // Increment count of threads blocked in a given thread pool. |
89 | 0 | identity->blocked_count_ptr->fetch_add(1, std::memory_order_relaxed); |
90 | 0 | } |
91 | |
|
92 | 0 | timeout = |
93 | 0 | !absl::synchronization_internal::Waiter::GetWaiter(identity)->Wait(t); |
94 | |
|
95 | 0 | if (identity->blocked_count_ptr != nullptr) { |
96 | 0 | identity->blocked_count_ptr->fetch_sub(1, std::memory_order_relaxed); |
97 | 0 | } |
98 | |
|
99 | 0 | identity->is_idle.store(false, std::memory_order_relaxed); |
100 | 0 | identity->wait_start.store(0, std::memory_order_relaxed); |
101 | 0 | return !timeout; |
102 | 0 | } |
103 | | |
104 | | } // extern "C" |
105 | | |
106 | | #endif // ABSL_LOW_LEVEL_ALLOC_MISSING |