ruy/blocking_counter.cc

/* Copyright 2019 Google LLC. All Rights Reserved.

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.
==============================================================================*/

#include "ruy/blocking_counter.h"

#include "ruy/check_macros.h"
#include "ruy/wait.h"

namespace ruy {

void BlockingCounter::Reset(int initial_count) {
  int old_count_value = count_.load(std::memory_order_relaxed);
  RUY_DCHECK_EQ(old_count_value, 0);
  (void)old_count_value;
  count_.store(initial_count, std::memory_order_release);
}

bool BlockingCounter::DecrementCount() {
  int old_count_value = count_.fetch_sub(1, std::memory_order_acq_rel);
  RUY_DCHECK_GT(old_count_value, 0);
  int count_value = old_count_value - 1;
  bool hit_zero = (count_value == 0);
  if (hit_zero) {
    std::lock_guard<std::mutex> lock(count_mutex_);
    count_cond_.notify_all();
  }
  return hit_zero;
}

void BlockingCounter::Wait(const Duration spin_duration) {
  const auto& condition = [this]() {
    return count_.load(std::memory_order_acquire) == 0;
  };
  ruy::Wait(condition, spin_duration, &count_cond_, &count_mutex_);
}

}  // namespace ruy