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
22 namespace art {
23
Barrier(int count)24 Barrier::Barrier(int count)
25 : count_(count),
26 lock_("GC barrier lock"),
27 condition_("GC barrier condition", lock_) {
28 }
29
Pass(Thread * self)30 void Barrier::Pass(Thread* self) {
31 MutexLock mu(self, lock_);
32 SetCountLocked(self, count_ - 1);
33 }
34
Wait(Thread * self)35 void Barrier::Wait(Thread* self) {
36 Increment(self, -1);
37 }
38
Init(Thread * self,int count)39 void Barrier::Init(Thread* self, int count) {
40 MutexLock mu(self, lock_);
41 SetCountLocked(self, count);
42 }
43
Increment(Thread * self,int delta)44 void 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 while (count_ != 0) {
56 condition_.Wait(self);
57 }
58 }
59
Increment(Thread * self,int delta,uint32_t timeout_ms)60 void 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 uint32_t timeout_ns = 0;
65 uint64_t abs_timeout = NanoTime() + MsToNs(timeout_ms);
66 for (;;) {
67 condition_.TimedWait(self, timeout_ms, timeout_ns);
68 if (count_ == 0) return;
69 // Compute time remaining on timeout.
70 uint64_t now = NanoTime();
71 int64_t time_left = abs_timeout - now;
72 if (time_left <= 0) return;
73 timeout_ns = time_left % (1000*1000);
74 timeout_ms = time_left / (1000*1000);
75 }
76 }
77 }
78
SetCountLocked(Thread * self,int count)79 void Barrier::SetCountLocked(Thread* self, int count) {
80 count_ = count;
81 if (count_ == 0) {
82 condition_.Broadcast(self);
83 }
84 }
85
~Barrier()86 Barrier::~Barrier() {
87 CHECK(!count_) << "Attempted to destroy barrier with non zero count";
88 }
89
90 } // namespace art
91