blob: d945a83d90a2e969dbc31bd6f804f7ec7933b594 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
|
// Copyright 2017 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_HEAP_BARRIER_H_
#define V8_HEAP_BARRIER_H_
#include "src/base/platform/condition-variable.h"
#include "src/base/platform/mutex.h"
namespace v8 {
namespace internal {
// Barrier that can be used once to synchronize a dynamic number of tasks
// working concurrently.
//
// Usage:
// void RunConcurrently(OneShotBarrier* shared_barrier) {
// shared_barrier->Start();
// do {
// {
// /* process work and create new work */
// barrier->NotifyAll();
// /* process work and create new work */
// }
// } while(!shared_barrier->Wait());
// }
//
// Note: If Start() is not called in time, e.g., because the first concurrent
// task is already done processing all work, then Done() will return true
// immediately.
class OneshotBarrier {
public:
OneshotBarrier() : tasks_(0), waiting_(0), done_(false) {}
void Start() {
base::LockGuard<base::Mutex> guard(&mutex_);
tasks_++;
}
void NotifyAll() {
base::LockGuard<base::Mutex> guard(&mutex_);
if (waiting_ > 0) condition_.NotifyAll();
}
bool Wait() {
base::LockGuard<base::Mutex> guard(&mutex_);
if (done_) return true;
DCHECK_LE(waiting_, tasks_);
waiting_++;
if (waiting_ == tasks_) {
done_ = true;
condition_.NotifyAll();
} else {
// Spurious wakeup is ok here.
condition_.Wait(&mutex_);
}
waiting_--;
return done_;
}
// Only valid to be called in a sequential setting.
bool DoneForTesting() const { return done_; }
private:
base::ConditionVariable condition_;
base::Mutex mutex_;
int tasks_;
int waiting_;
bool done_;
};
} // namespace internal
} // namespace v8
#endif // V8_HEAP_BARRIER_H_
|
