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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 
     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 
     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 
     50 void SetBlockingObserverForCurrentThread(BlockingObserver* blocking_observer) {
     51   DCHECK(!tls_blocking_observer.Get().Get());
     52   tls_blocking_observer.Get().Set(blocking_observer);
     53 }
     54 
     55 void ClearBlockingObserverForTesting() {
     56   tls_blocking_observer.Get().Set(nullptr);
     57 }
     58 
     59 ScopedClearBlockingObserverForTesting::ScopedClearBlockingObserverForTesting()
     60     : blocking_observer_(tls_blocking_observer.Get().Get()) {
     61   tls_blocking_observer.Get().Set(nullptr);
     62 }
     63 
     64 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