Abseil Common Libraries (C++) (grcp 依赖)
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91 lines
3.5 KiB
91 lines
3.5 KiB
// Copyright 2017 The Abseil Authors. |
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// |
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// Licensed under the Apache License, Version 2.0 (the "License"); |
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// you may not use this file except in compliance with the License. |
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// You may obtain a copy of the License at |
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// |
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// https://www.apache.org/licenses/LICENSE-2.0 |
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// |
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// Unless required by applicable law or agreed to in writing, software |
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// distributed under the License is distributed on an "AS IS" BASIS, |
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
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// See the License for the specific language governing permissions and |
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// limitations under the License. |
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#ifndef ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_ |
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#define ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_ |
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// Operations to make atomic transitions on a word, and to allow |
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// waiting for those transitions to become possible. |
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#include <stdint.h> |
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#include <atomic> |
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#include "absl/base/internal/scheduling_mode.h" |
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namespace absl { |
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ABSL_NAMESPACE_BEGIN |
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namespace base_internal { |
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// SpinLockWait() waits until it can perform one of several transitions from |
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// "from" to "to". It returns when it performs a transition where done==true. |
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struct SpinLockWaitTransition { |
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uint32_t from; |
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uint32_t to; |
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bool done; |
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}; |
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// Wait until *w can transition from trans[i].from to trans[i].to for some i |
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// satisfying 0<=i<n && trans[i].done, atomically make the transition, |
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// then return the old value of *w. Make any other atomic transitions |
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// where !trans[i].done, but continue waiting. |
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uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n, |
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const SpinLockWaitTransition trans[], |
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SchedulingMode scheduling_mode); |
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// If possible, wake some thread that has called SpinLockDelay(w, ...). If `all` |
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// is true, wake all such threads. On some systems, this may be a no-op; on |
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// those systems, threads calling SpinLockDelay() will always wake eventually |
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// even if SpinLockWake() is never called. |
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void SpinLockWake(std::atomic<uint32_t> *w, bool all); |
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// Wait for an appropriate spin delay on iteration "loop" of a |
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// spin loop on location *w, whose previously observed value was "value". |
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// SpinLockDelay() may do nothing, may yield the CPU, may sleep a clock tick, |
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// or may wait for a call to SpinLockWake(w). |
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void SpinLockDelay(std::atomic<uint32_t> *w, uint32_t value, int loop, |
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base_internal::SchedulingMode scheduling_mode); |
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// Helper used by AbslInternalSpinLockDelay. |
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// Returns a suggested delay in nanoseconds for iteration number "loop". |
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int SpinLockSuggestedDelayNS(int loop); |
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} // namespace base_internal |
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ABSL_NAMESPACE_END |
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} // namespace absl |
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// In some build configurations we pass --detect-odr-violations to the |
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// gold linker. This causes it to flag weak symbol overrides as ODR |
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// violations. Because ODR only applies to C++ and not C, |
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// --detect-odr-violations ignores symbols not mangled with C++ names. |
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// By changing our extension points to be extern "C", we dodge this |
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// check. |
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extern "C" { |
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void AbslInternalSpinLockWake(std::atomic<uint32_t> *w, bool all); |
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void AbslInternalSpinLockDelay( |
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std::atomic<uint32_t> *w, uint32_t value, int loop, |
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absl::base_internal::SchedulingMode scheduling_mode); |
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} |
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inline void absl::base_internal::SpinLockWake(std::atomic<uint32_t> *w, |
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bool all) { |
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AbslInternalSpinLockWake(w, all); |
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} |
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inline void absl::base_internal::SpinLockDelay( |
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std::atomic<uint32_t> *w, uint32_t value, int loop, |
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absl::base_internal::SchedulingMode scheduling_mode) { |
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AbslInternalSpinLockDelay(w, value, loop, scheduling_mode); |
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} |
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#endif // ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_
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