1/*
2 * Copyright (C) 2012 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#include "barrier.h"
18
19#include "base/mutex.h"
20#include "thread.h"
21
22namespace art {
23
24Barrier::Barrier(int count)
25    : count_(count),
26      lock_("GC barrier lock"),
27      condition_("GC barrier condition", lock_) {
28}
29
30void Barrier::Pass(Thread* self) {
31  MutexLock mu(self, lock_);
32  SetCountLocked(self, count_ - 1);
33}
34
35void Barrier::Wait(Thread* self) {
36  Increment(self, -1);
37}
38
39void Barrier::Init(Thread* self, int count) {
40  MutexLock mu(self, lock_);
41  SetCountLocked(self, count);
42}
43
44void Barrier::Increment(Thread* self, int delta) {
45  MutexLock mu(self, lock_);
46  SetCountLocked(self, count_ + delta);
47
48  // Increment the count.  If it becomes zero after the increment
49  // then all the threads have already passed the barrier.  If
50  // it is non-zero then there is still one or more threads
51  // that have not yet called the Pass function.  When the
52  // Pass function is called by the last thread, the count will
53  // be decremented to zero and a Broadcast will be made on the
54  // condition variable, thus waking this up.
55  if (count_ != 0) {
56    condition_.Wait(self);
57  }
58}
59
60void Barrier::Increment(Thread* self, int delta, uint32_t timeout_ms) {
61  MutexLock mu(self, lock_);
62  SetCountLocked(self, count_ + delta);
63  if (count_ != 0) {
64    condition_.TimedWait(self, timeout_ms, 0);
65  }
66}
67
68void Barrier::SetCountLocked(Thread* self, int count) {
69  count_ = count;
70  if (count_ == 0) {
71    condition_.Broadcast(self);
72  }
73}
74
75Barrier::~Barrier() {
76  CHECK(!count_) << "Attempted to destroy barrier with non zero count";
77}
78
79}  // namespace art
80