3af63b0dc9
The AsyncInvoker destructor waits for all invoked tasks to be complete (in other words, all AsyncClosures to be destructed). They were using an event to wake up the destructor, but a race made it possible for this event to be dereferenced after it's destroyed. This CL makes the event reference counted, such that if the destructor runs right after AsyncClosure decrements "pending_invocations_", setting the event will be a no-op, and the event will be destructed in the AsyncClosure destructor. This CL also fixes a deadlock that may occur for "re-entrant" invocations. The deadlock occurs if the AsyncInvoker is destroyed on thread A while a task on thread B is running, which AsyncInvokes a task back on thread A. This was causing pending_invocations_ to end up negative, because an AsyncClosure that's never added to a thread's message queue (due to the "destroying_" flag) caused the count to be decremented but not incremented. BUG=webrtc:7656 Review-Url: https://codereview.webrtc.org/2885143005 Cr-Commit-Position: refs/heads/master@{#19278}
64 lines
2.1 KiB
C++
64 lines
2.1 KiB
C++
/*
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* Copyright 2014 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef WEBRTC_RTC_BASE_ASYNCINVOKER_INL_H_
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#define WEBRTC_RTC_BASE_ASYNCINVOKER_INL_H_
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#include "webrtc/rtc_base/bind.h"
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#include "webrtc/rtc_base/criticalsection.h"
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#include "webrtc/rtc_base/event.h"
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#include "webrtc/rtc_base/messagehandler.h"
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#include "webrtc/rtc_base/refcountedobject.h"
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#include "webrtc/rtc_base/scoped_ref_ptr.h"
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#include "webrtc/rtc_base/sigslot.h"
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#include "webrtc/rtc_base/thread.h"
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#include "webrtc/rtc_base/thread_annotations.h"
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namespace rtc {
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class AsyncInvoker;
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// Helper class for AsyncInvoker. Runs a task and triggers a callback
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// on the calling thread if necessary.
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class AsyncClosure {
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public:
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explicit AsyncClosure(AsyncInvoker* invoker);
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virtual ~AsyncClosure();
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// Runs the asynchronous task, and triggers a callback to the calling
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// thread if needed. Should be called from the target thread.
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virtual void Execute() = 0;
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protected:
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AsyncInvoker* invoker_;
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// Reference counted so that if the AsyncInvoker destructor finishes before
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// an AsyncClosure's destructor that's about to call
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// "invocation_complete_->Set()", it's not dereferenced after being
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// destroyed.
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scoped_refptr<RefCountedObject<Event>> invocation_complete_;
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};
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// Simple closure that doesn't trigger a callback for the calling thread.
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template <class FunctorT>
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class FireAndForgetAsyncClosure : public AsyncClosure {
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public:
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explicit FireAndForgetAsyncClosure(AsyncInvoker* invoker,
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const FunctorT& functor)
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: AsyncClosure(invoker), functor_(functor) {}
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virtual void Execute() {
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functor_();
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}
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private:
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FunctorT functor_;
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};
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} // namespace rtc
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#endif // WEBRTC_RTC_BASE_ASYNCINVOKER_INL_H_
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