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 <android-base/logging.h>
20
21 #include "base/aborting.h"
22 #include "base/mutex.h"
23 #include "base/time_utils.h"
24 #include "thread.h"
25
26 namespace art {
27
Barrier(int count)28 Barrier::Barrier(int count)
29 : count_(count),
30 lock_("GC barrier lock", kThreadSuspendCountLock),
31 condition_("GC barrier condition", lock_) {
32 }
33
34 template void Barrier::Increment<Barrier::kAllowHoldingLocks>(Thread* self, int delta);
35 template void Barrier::Increment<Barrier::kDisallowHoldingLocks>(Thread* self, int delta);
36
Pass(Thread * self)37 void Barrier::Pass(Thread* self) {
38 MutexLock mu(self, lock_);
39 SetCountLocked(self, count_ - 1);
40 }
41
Wait(Thread * self)42 void Barrier::Wait(Thread* self) {
43 Increment(self, -1);
44 }
45
Init(Thread * self,int count)46 void Barrier::Init(Thread* self, int count) {
47 MutexLock mu(self, lock_);
48 SetCountLocked(self, count);
49 }
50
51 template <Barrier::LockHandling locks>
Increment(Thread * self,int delta)52 void Barrier::Increment(Thread* self, int delta) {
53 MutexLock mu(self, lock_);
54 SetCountLocked(self, count_ + delta);
55
56 // Increment the count. If it becomes zero after the increment
57 // then all the threads have already passed the barrier. If
58 // it is non-zero then there is still one or more threads
59 // that have not yet called the Pass function. When the
60 // Pass function is called by the last thread, the count will
61 // be decremented to zero and a Broadcast will be made on the
62 // condition variable, thus waking this up.
63 while (count_ != 0) {
64 if (locks == kAllowHoldingLocks) {
65 condition_.WaitHoldingLocks(self);
66 } else {
67 condition_.Wait(self);
68 }
69 }
70 }
71
Increment(Thread * self,int delta,uint32_t timeout_ms)72 bool Barrier::Increment(Thread* self, int delta, uint32_t timeout_ms) {
73 MutexLock mu(self, lock_);
74 SetCountLocked(self, count_ + delta);
75 bool timed_out = false;
76 if (count_ != 0) {
77 uint32_t timeout_ns = 0;
78 uint64_t abs_timeout = NanoTime() + MsToNs(timeout_ms);
79 for (;;) {
80 timed_out = condition_.TimedWait(self, timeout_ms, timeout_ns);
81 if (timed_out || count_ == 0) return timed_out;
82 // Compute time remaining on timeout.
83 uint64_t now = NanoTime();
84 int64_t time_left = abs_timeout - now;
85 if (time_left <= 0) return true;
86 timeout_ns = time_left % (1000*1000);
87 timeout_ms = time_left / (1000*1000);
88 }
89 }
90 return timed_out;
91 }
92
GetCount(Thread * self)93 int Barrier::GetCount(Thread* self) {
94 MutexLock mu(self, lock_);
95 return count_;
96 }
97
SetCountLocked(Thread * self,int count)98 void Barrier::SetCountLocked(Thread* self, int count) {
99 count_ = count;
100 if (count == 0) {
101 condition_.Broadcast(self);
102 }
103 }
104
~Barrier()105 Barrier::~Barrier() {
106 if (gAborting == 0) {
107 // Only check when not aborting.
108 CHECK_EQ(count_, 0) << "Attempted to destroy barrier with non zero count";
109 } else {
110 if (count_ != 0) {
111 LOG(WARNING) << "Attempted to destroy barrier with non zero count " << count_;
112 }
113 }
114 }
115
116 } // namespace art
117