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/logging.h"
20 #include "base/mutex.h"
21 #include "base/time_utils.h"
22 #include "thread.h"
23
24 namespace art {
25
Barrier(int count)26 Barrier::Barrier(int count)
27 : count_(count),
28 lock_("GC barrier lock", kThreadSuspendCountLock),
29 condition_("GC barrier condition", lock_) {
30 }
31
Pass(Thread * self)32 void Barrier::Pass(Thread* self) {
33 MutexLock mu(self, lock_);
34 SetCountLocked(self, count_ - 1);
35 }
36
Wait(Thread * self)37 void Barrier::Wait(Thread* self) {
38 Increment(self, -1);
39 }
40
Init(Thread * self,int count)41 void Barrier::Init(Thread* self, int count) {
42 MutexLock mu(self, lock_);
43 SetCountLocked(self, count);
44 }
45
Increment(Thread * self,int delta)46 void Barrier::Increment(Thread* self, int delta) {
47 MutexLock mu(self, lock_);
48 SetCountLocked(self, count_ + delta);
49
50 // Increment the count. If it becomes zero after the increment
51 // then all the threads have already passed the barrier. If
52 // it is non-zero then there is still one or more threads
53 // that have not yet called the Pass function. When the
54 // Pass function is called by the last thread, the count will
55 // be decremented to zero and a Broadcast will be made on the
56 // condition variable, thus waking this up.
57 while (count_ != 0) {
58 condition_.Wait(self);
59 }
60 }
61
Increment(Thread * self,int delta,uint32_t timeout_ms)62 bool Barrier::Increment(Thread* self, int delta, uint32_t timeout_ms) {
63 MutexLock mu(self, lock_);
64 SetCountLocked(self, count_ + delta);
65 bool timed_out = false;
66 if (count_ != 0) {
67 uint32_t timeout_ns = 0;
68 uint64_t abs_timeout = NanoTime() + MsToNs(timeout_ms);
69 for (;;) {
70 timed_out = condition_.TimedWait(self, timeout_ms, timeout_ns);
71 if (timed_out || count_ == 0) return timed_out;
72 // Compute time remaining on timeout.
73 uint64_t now = NanoTime();
74 int64_t time_left = abs_timeout - now;
75 if (time_left <= 0) return true;
76 timeout_ns = time_left % (1000*1000);
77 timeout_ms = time_left / (1000*1000);
78 }
79 }
80 return timed_out;
81 }
82
SetCountLocked(Thread * self,int count)83 void Barrier::SetCountLocked(Thread* self, int count) {
84 count_ = count;
85 if (count == 0) {
86 condition_.Broadcast(self);
87 }
88 }
89
~Barrier()90 Barrier::~Barrier() {
91 if (gAborting == 0) {
92 // Only check when not aborting.
93 CHECK_EQ(count_, 0) << "Attempted to destroy barrier with non zero count";
94 } else {
95 if (count_ != 0) {
96 LOG(WARNING) << "Attempted to destroy barrier with non zero count " << count_;
97 }
98 }
99 }
100
101 } // namespace art
102