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1 // Copyright 2017 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4 
5 #include "base/threading/scoped_blocking_call.h"
6 
7 #include "base/lazy_instance.h"
8 #include "base/threading/thread_local.h"
9 
10 namespace base {
11 
12 namespace {
13 
14 LazyInstance<ThreadLocalPointer<internal::BlockingObserver>>::Leaky
15     tls_blocking_observer = LAZY_INSTANCE_INITIALIZER;
16 
17 // Last ScopedBlockingCall instantiated on this thread.
18 LazyInstance<ThreadLocalPointer<ScopedBlockingCall>>::Leaky
19     tls_last_scoped_blocking_call = LAZY_INSTANCE_INITIALIZER;
20 
21 }  // namespace
22 
ScopedBlockingCall(BlockingType blocking_type)23 ScopedBlockingCall::ScopedBlockingCall(BlockingType blocking_type)
24     : blocking_observer_(tls_blocking_observer.Get().Get()),
25       previous_scoped_blocking_call_(tls_last_scoped_blocking_call.Get().Get()),
26       is_will_block_(blocking_type == BlockingType::WILL_BLOCK ||
27                      (previous_scoped_blocking_call_ &&
28                       previous_scoped_blocking_call_->is_will_block_)) {
29   tls_last_scoped_blocking_call.Get().Set(this);
30 
31   if (blocking_observer_) {
32     if (!previous_scoped_blocking_call_) {
33       blocking_observer_->BlockingStarted(blocking_type);
34     } else if (blocking_type == BlockingType::WILL_BLOCK &&
35                !previous_scoped_blocking_call_->is_will_block_) {
36       blocking_observer_->BlockingTypeUpgraded();
37     }
38   }
39 }
40 
~ScopedBlockingCall()41 ScopedBlockingCall::~ScopedBlockingCall() {
42   DCHECK_EQ(this, tls_last_scoped_blocking_call.Get().Get());
43   tls_last_scoped_blocking_call.Get().Set(previous_scoped_blocking_call_);
44   if (blocking_observer_ && !previous_scoped_blocking_call_)
45     blocking_observer_->BlockingEnded();
46 }
47 
48 namespace internal {
49 
SetBlockingObserverForCurrentThread(BlockingObserver * blocking_observer)50 void SetBlockingObserverForCurrentThread(BlockingObserver* blocking_observer) {
51   DCHECK(!tls_blocking_observer.Get().Get());
52   tls_blocking_observer.Get().Set(blocking_observer);
53 }
54 
ClearBlockingObserverForTesting()55 void ClearBlockingObserverForTesting() {
56   tls_blocking_observer.Get().Set(nullptr);
57 }
58 
ScopedClearBlockingObserverForTesting()59 ScopedClearBlockingObserverForTesting::ScopedClearBlockingObserverForTesting()
60     : blocking_observer_(tls_blocking_observer.Get().Get()) {
61   tls_blocking_observer.Get().Set(nullptr);
62 }
63 
64 ScopedClearBlockingObserverForTesting::
~ScopedClearBlockingObserverForTesting()65     ~ScopedClearBlockingObserverForTesting() {
66   DCHECK(!tls_blocking_observer.Get().Get());
67   tls_blocking_observer.Get().Set(blocking_observer_);
68 }
69 
70 }  // namespace internal
71 
72 }  // namespace base
73