text: /*
   * Copyright (C) 2012 The Android Open Source Project
   *
   * 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 "barrier.h"
  
  #include "base/mutex.h"
  #include "base/time_utils.h"
  #include "thread.h"
  
  namespace art {
  
  Barrier::Barrier(int count)
      : count_(count),
        lock_("GC barrier lock", kThreadSuspendCountLock),
        condition_("GC barrier condition", lock_) {
  }
  
  void Barrier::Pass(Thread* self) {
    MutexLock mu(self, lock_);
    SetCountLocked(self, count_ - 1);
  }
  
  void Barrier::Wait(Thread* self) {
    Increment(self, -1);
  }
  
  void Barrier::Init(Thread* self, int count) {
    MutexLock mu(self, lock_);
    SetCountLocked(self, count);
  }
  
  void Barrier::Increment(Thread* self, int delta) {
    MutexLock mu(self, lock_);
    SetCountLocked(self, count_ + delta);
  
    // Increment the count.  If it becomes zero after the increment
    // then all the threads have already passed the barrier.  If
    // it is non-zero then there is still one or more threads
    // that have not yet called the Pass function.  When the
    // Pass function is called by the last thread, the count will
    // be decremented to zero and a Broadcast will be made on the
    // condition variable, thus waking this up.
    while (count_ != 0) {
      condition_.Wait(self);
    }
  }
  
  bool Barrier::Increment(Thread* self, int delta, uint32_t timeout_ms) {
    MutexLock mu(self, lock_);
    SetCountLocked(self, count_ + delta);
    bool timed_out = false;
    if (count_ != 0) {
      uint32_t timeout_ns = 0;
      uint64_t abs_timeout = NanoTime() + MsToNs(timeout_ms);
      for (;;) {
        timed_out = condition_.TimedWait(self, timeout_ms, timeout_ns);
        if (timed_out || count_ == 0) return timed_out;
        // Compute time remaining on timeout.
        uint64_t now = NanoTime();
        int64_t time_left = abs_timeout - now;
        if (time_left <= 0) return true;
        timeout_ns = time_left % (1000*1000);
        timeout_ms = time_left / (1000*1000);
      }
    }
    return timed_out;
  }
  
  void Barrier::SetCountLocked(Thread* self, int count) {
    count_ = count;
    if (count == 0) {
      condition_.Broadcast(self);
    }
  }
  
  Barrier::~Barrier() {
    CHECK_EQ(count_, 0) << "Attempted to destroy barrier with non zero count";
  }
  
  }  // namespace art
  