Abseil Common Libraries (C++) (grcp 依赖)
https://abseil.io/
You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
91 lines
3.6 KiB
91 lines
3.6 KiB
// Copyright 2017 The Abseil Authors. |
|
// |
|
// Licensed 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. |
|
|
|
#ifndef ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_ |
|
#define ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_ |
|
|
|
// Operations to make atomic transitions on a word, and to allow |
|
// waiting for those transitions to become possible. |
|
|
|
#include <stdint.h> |
|
#include <atomic> |
|
|
|
#include "absl/base/internal/scheduling_mode.h" |
|
|
|
namespace absl { |
|
namespace base_internal { |
|
|
|
// SpinLockWait() waits until it can perform one of several transitions from |
|
// "from" to "to". It returns when it performs a transition where done==true. |
|
struct SpinLockWaitTransition { |
|
uint32_t from; |
|
uint32_t to; |
|
bool done; |
|
}; |
|
|
|
// Wait until *w can transition from trans[i].from to trans[i].to for some i |
|
// satisfying 0<=i<n && trans[i].done, atomically make the transition, |
|
// then return the old value of *w. Make any other atomic transitions |
|
// where !trans[i].done, but continue waiting. |
|
uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n, |
|
const SpinLockWaitTransition trans[], |
|
SchedulingMode scheduling_mode); |
|
|
|
// If possible, wake some thread that has called SpinLockDelay(w, ...). If |
|
// "all" is true, wake all such threads. This call is a hint, and on some |
|
// systems it may be a no-op; threads calling SpinLockDelay() will always wake |
|
// eventually even if SpinLockWake() is never called. |
|
void SpinLockWake(std::atomic<uint32_t> *w, bool all); |
|
|
|
// Wait for an appropriate spin delay on iteration "loop" of a |
|
// spin loop on location *w, whose previously observed value was "value". |
|
// SpinLockDelay() may do nothing, may yield the CPU, may sleep a clock tick, |
|
// or may wait for a delay that can be truncated by a call to SpinLockWake(w). |
|
// In all cases, it must return in bounded time even if SpinLockWake() is not |
|
// called. |
|
void SpinLockDelay(std::atomic<uint32_t> *w, uint32_t value, int loop, |
|
base_internal::SchedulingMode scheduling_mode); |
|
|
|
// Helper used by AbslInternalSpinLockDelay. |
|
// Returns a suggested delay in nanoseconds for iteration number "loop". |
|
int SpinLockSuggestedDelayNS(int loop); |
|
|
|
} // namespace base_internal |
|
} // namespace absl |
|
|
|
// In some build configurations we pass --detect-odr-violations to the |
|
// gold linker. This causes it to flag weak symbol overrides as ODR |
|
// violations. Because ODR only applies to C++ and not C, |
|
// --detect-odr-violations ignores symbols not mangled with C++ names. |
|
// By changing our extension points to be extern "C", we dodge this |
|
// check. |
|
extern "C" { |
|
void AbslInternalSpinLockWake(std::atomic<uint32_t> *w, bool all); |
|
void AbslInternalSpinLockDelay( |
|
std::atomic<uint32_t> *w, uint32_t value, int loop, |
|
absl::base_internal::SchedulingMode scheduling_mode); |
|
} |
|
|
|
inline void absl::base_internal::SpinLockWake(std::atomic<uint32_t> *w, |
|
bool all) { |
|
AbslInternalSpinLockWake(w, all); |
|
} |
|
|
|
inline void absl::base_internal::SpinLockDelay( |
|
std::atomic<uint32_t> *w, uint32_t value, int loop, |
|
absl::base_internal::SchedulingMode scheduling_mode) { |
|
AbslInternalSpinLockDelay(w, value, loop, scheduling_mode); |
|
} |
|
|
|
#endif // ABSL_BASE_INTERNAL_SPINLOCK_WAIT_H_
|
|
|