chromium/third_party/abseil-cpp/absl/base/internal/spinlock_wait.cc

// 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
//
//      https://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.

// The OS-specific header included below must provide two calls:
// AbslInternalSpinLockDelay() and AbslInternalSpinLockWake().
// See spinlock_wait.h for the specs.

#include <atomic>
#include <cstdint>

#include "absl/base/internal/spinlock_wait.h"

#if defined(_WIN32)
#include "absl/base/internal/spinlock_win32.inc"
#elif defined(__linux__)
#include "absl/base/internal/spinlock_linux.inc"
#elif defined(__akaros__)
#include "absl/base/internal/spinlock_akaros.inc"
#else
#include "absl/base/internal/spinlock_posix.inc"
#endif

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace base_internal {

// See spinlock_wait.h for spec.
uint32_t SpinLockWait(std::atomic<uint32_t> *w, int n,
                      const SpinLockWaitTransition trans[],
                      base_internal::SchedulingMode scheduling_mode) { … }

static std::atomic<uint64_t> delay_rand;

// Return a suggested delay in nanoseconds for iteration number "loop"
int SpinLockSuggestedDelayNS(int loop) { … }

}  // namespace base_internal
ABSL_NAMESPACE_END
}  // namespace absl