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