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