mirror of
https://github.com/mozilla/gecko-dev.git
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348 lines
9.8 KiB
C++
348 lines
9.8 KiB
C++
/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
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* vim: sw=4 ts=4 et :
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_BlockingResourceBase_h
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#define mozilla_BlockingResourceBase_h
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#include "prlog.h"
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#include "nscore.h"
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#include "nsDebug.h"
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#include "nsError.h"
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#include "nsTraceRefcnt.h"
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#ifdef DEBUG
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#include "prinit.h"
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#include "prthread.h"
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#include "nsStringGlue.h"
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#include "mozilla/DeadlockDetector.h"
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#include "nsXPCOM.h"
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#endif
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//
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// This header is not meant to be included by client code.
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//
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namespace mozilla {
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/**
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* BlockingResourceBase
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* Base class of resources that might block clients trying to acquire them.
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* Does debugging and deadlock detection in DEBUG builds.
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**/
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class NS_COM_GLUE BlockingResourceBase
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{
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public:
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// Needs to be kept in sync with kResourceTypeNames.
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enum BlockingResourceType { eMutex, eReentrantMonitor, eCondVar };
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/**
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* kResourceTypeName
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* Human-readable version of BlockingResourceType enum.
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*/
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static const char* const kResourceTypeName[];
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#ifdef DEBUG
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private:
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// forward declaration for the following typedef
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struct DeadlockDetectorEntry;
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// ``DDT'' = ``Deadlock Detector Type''
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typedef DeadlockDetector<DeadlockDetectorEntry> DDT;
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/**
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* DeadlockDetectorEntry
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* We free BlockingResources, but we never free entries in the
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* deadlock detector. This struct outlives its BlockingResource
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* and preserves all the state needed to print subsequent
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* error messages.
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*
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* These objects are owned by the deadlock detector.
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*/
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struct DeadlockDetectorEntry
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{
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DeadlockDetectorEntry(const char* aName,
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BlockingResourceType aType) :
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mName(aName),
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mType(aType),
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mAcquisitionContext(CallStack::kNone)
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{
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NS_ABORT_IF_FALSE(mName, "Name must be nonnull");
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}
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/**
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* Print
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* Write a description of this blocking resource to |out|. If
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* the resource appears to be currently acquired, the current
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* acquisition context is printed and true is returned.
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* Otherwise, we print the context from |aFirstSeen|, the
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* first acquisition from which the code calling |Print()|
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* became interested in us, and return false. |Print()| can
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* be forced to print the context from |aFirstSeen| regardless
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* by passing |aPrintFirstSeenCx=true|.
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*
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* *NOT* thread safe. Reads |mAcquisitionContext| without
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* synchronization, but this will not cause correctness
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* problems.
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*
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* FIXME bug 456272: hack alert: because we can't write call
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* contexts into strings, all info is written to stderr, but
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* only some info is written into |out|
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*/
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bool Print(const DDT::ResourceAcquisition& aFirstSeen,
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nsACString& out,
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bool aPrintFirstSeenCx=false) const;
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/**
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* mName
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* A descriptive name for this resource. Used in error
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* messages etc.
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*/
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const char* mName;
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/**
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* mType
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* The more specific type of this resource. Used to implement
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* special semantics (e.g., reentrancy of monitors).
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**/
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BlockingResourceType mType;
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/**
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* mAcquisitionContext
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* The calling context from which this resource was acquired, or
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* |CallStack::kNone| if it is currently free (or freed).
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*/
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CallStack mAcquisitionContext;
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};
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protected:
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/**
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* BlockingResourceBase
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* Initialize this blocking resource. Also hooks the resource into
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* instrumentation code.
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*
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* Thread safe.
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*
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* @param aName A meaningful, unique name that can be used in
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* error messages, et al.
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* @param aType The specific type of |this|, if any.
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**/
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BlockingResourceBase(const char* aName, BlockingResourceType aType);
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~BlockingResourceBase();
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/**
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* CheckAcquire
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*
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* Thread safe.
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*
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* @param aCallContext the client's calling context from which the
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* original acquisition request was made.
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**/
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void CheckAcquire(const CallStack& aCallContext);
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/**
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* Acquire
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*
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* @param aCallContext the client's calling context from which the
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* original acquisition request was made.
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**/
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void Acquire(const CallStack& aCallContext); //NS_NEEDS_RESOURCE(this)
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/**
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* Release
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* Remove this resource from the current thread's acquisition chain.
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* The resource does not have to be at the front of the chain, although
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* it is confusing to release resources in a different order than they
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* are acquired. This generates a warning.
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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**/
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void Release(); //NS_NEEDS_RESOURCE(this)
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/**
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* PrintCycle
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* Append to |out| detailed information about the circular
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* dependency in |cycle|. Returns true if it *appears* that this
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* cycle may represent an imminent deadlock, but this is merely a
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* heuristic; the value returned may be a false positive or false
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* negative.
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*
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* *NOT* thread safe. Calls |Print()|.
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*
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* FIXME bug 456272 hack alert: because we can't write call
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* contexts into strings, all info is written to stderr, but only
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* some info is written into |out|
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*/
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static bool PrintCycle(const DDT::ResourceAcquisitionArray* cycle,
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nsACString& out);
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/**
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* ResourceChainFront
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*
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* Thread safe.
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*
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* @return the front of the resource acquisition chain, i.e., the last
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* resource acquired.
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*/
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static BlockingResourceBase* ResourceChainFront()
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{
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return (BlockingResourceBase*)
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PR_GetThreadPrivate(sResourceAcqnChainFrontTPI);
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}
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/**
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* ResourceChainPrev
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*/
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static BlockingResourceBase*
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ResourceChainPrev(const BlockingResourceBase* aResource)
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{
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return aResource->mChainPrev;
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} //NS_NEEDS_RESOURCE(this)
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/**
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* ResourceChainAppend
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* Set |this| to the front of the resource acquisition chain, and link
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* |this| to |aPrev|.
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*/
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void ResourceChainAppend(BlockingResourceBase* aPrev)
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{
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mChainPrev = aPrev;
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PR_SetThreadPrivate(sResourceAcqnChainFrontTPI, this);
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} //NS_NEEDS_RESOURCE(this)
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/**
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* ResourceChainRemove
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* Remove |this| from the front of the resource acquisition chain.
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*/
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void ResourceChainRemove()
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{
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NS_ASSERTION(this == ResourceChainFront(), "not at chain front");
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PR_SetThreadPrivate(sResourceAcqnChainFrontTPI, mChainPrev);
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} //NS_NEEDS_RESOURCE(this)
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/**
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* GetAcquisitionContext
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* Return the calling context from which this resource was acquired,
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* or CallStack::kNone if it's currently free.
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*/
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CallStack
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GetAcquisitionContext()
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{
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return mDDEntry->mAcquisitionContext;
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}
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/**
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* SetAcquisitionContext
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* Set the calling context from which this resource was acquired.
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*
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* *NOT* thread safe. Requires ownership of underlying resource.
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*/
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void
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SetAcquisitionContext(CallStack aAcquisitionContext)
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{
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mDDEntry->mAcquisitionContext = aAcquisitionContext;
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}
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/**
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* mChainPrev
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* A series of resource acquisitions creates a chain of orders. This
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* chain is implemented as a linked list; |mChainPrev| points to the
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* resource most recently Acquire()'d before this one.
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**/
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BlockingResourceBase* mChainPrev;
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private:
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/**
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* mDDEntry
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* The key for this BlockingResourceBase in the deadlock detector.
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*/
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DeadlockDetectorEntry* mDDEntry;
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/**
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* sCallOnce
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* Ensures static members are initialized only once, and in a
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* thread-safe way.
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*/
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static PRCallOnceType sCallOnce;
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/**
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* sResourceAcqnChainFrontTPI
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* Thread-private index to the front of each thread's resource
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* acquisition chain.
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*/
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static unsigned sResourceAcqnChainFrontTPI;
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/**
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* sDeadlockDetector
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* Does as named.
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*/
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static DDT* sDeadlockDetector;
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/**
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* InitStatics
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* Inititialize static members of BlockingResourceBase that can't
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* be statically initialized.
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*
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* *NOT* thread safe.
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*/
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static PRStatus InitStatics() {
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PR_NewThreadPrivateIndex(&sResourceAcqnChainFrontTPI, 0);
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sDeadlockDetector = new DDT();
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if (!sDeadlockDetector)
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NS_RUNTIMEABORT("can't allocate deadlock detector");
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return PR_SUCCESS;
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}
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/**
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* Shutdown
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* Free static members.
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*
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* *NOT* thread safe.
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*/
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static void Shutdown() {
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delete sDeadlockDetector;
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sDeadlockDetector = 0;
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}
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# ifdef MOZILLA_INTERNAL_API
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// so it can call BlockingResourceBase::Shutdown()
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friend void LogTerm();
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# endif // ifdef MOZILLA_INTERNAL_API
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#else // non-DEBUG implementation
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BlockingResourceBase(const char* aName, BlockingResourceType aType)
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{
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}
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~BlockingResourceBase()
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{
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}
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#endif
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};
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} // namespace mozilla
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#endif // mozilla_BlockingResourceBase_h
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