ydb/contrib/libs/clang18-rt/lib/scudo/standalone/condition_variable.h

//===-- condition_variable.h ------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

#ifndef SCUDO_CONDITION_VARIABLE_H_
#define SCUDO_CONDITION_VARIABLE_H_

#include "condition_variable_base.h"

#include "common.h"
#include "platform.h"

#include "condition_variable_linux.h"

namespace scudo {

// A default implementation of default condition variable. It doesn't do a real
// `wait`, instead it spins a short amount of time only.
class ConditionVariableDummy
    : public ConditionVariableBase<ConditionVariableDummy> {
public:
  void notifyAllImpl(UNUSED HybridMutex &M) REQUIRES(M) {}

  void waitImpl(UNUSED HybridMutex &M) REQUIRES(M) {
    M.unlock();

    constexpr u32 SpinTimes = 64;
    volatile u32 V = 0;
    for (u32 I = 0; I < SpinTimes; ++I) {
      u32 Tmp = V + 1;
      V = Tmp;
    }

    M.lock();
  }
};

template <typename Config, typename = const bool>
struct ConditionVariableState {
  static constexpr bool enabled() { return false; }
  // This is only used for compilation purpose so that we won't end up having
  // many conditional compilations. If you want to use `ConditionVariableDummy`,
  // define `ConditionVariableT` in your allocator configuration. See
  // allocator_config.h for more details.
  using ConditionVariableT = ConditionVariableDummy;
};

template <typename Config>
struct ConditionVariableState<Config, decltype(Config::UseConditionVariable)> {
  static constexpr bool enabled() { return Config::UseConditionVariable; }
  using ConditionVariableT = typename Config::ConditionVariableT;
};

} // namespace scudo

#endif // SCUDO_CONDITION_VARIABLE_H_