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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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
#ifndef mozilla_BlockingResourceBase_h
#define mozilla_BlockingResourceBase_h
#include "mozilla/MemoryReporting.h"
#include "mozilla/ThreadLocal.h"
#include "mozilla/Attributes.h"
#include "nscore.h"
#include "nsDebug.h"
#include "prtypes.h"
#ifdef DEBUG
// NB: Comment this out to enable callstack tracking.
# define MOZ_CALLSTACK_DISABLED
# include "prinit.h"
# ifndef MOZ_CALLSTACK_DISABLED
# include "mozilla/Maybe.h"
# include "nsTArray.h"
# endif
#endif
//
// This header is not meant to be included by client code.
//
namespace mozilla {
#ifdef DEBUG
template <class T>
class DeadlockDetector;
#endif
/**
* BlockingResourceBase
* Base class of resources that might block clients trying to acquire them.
* Does debugging and deadlock detection in DEBUG builds.
**/
class BlockingResourceBase {
public:
// Needs to be kept in sync with kResourceTypeNames.
enum BlockingResourceType {
eMutex,
eReentrantMonitor,
eCondVar,
eRecursiveMutex
};
/**
* kResourceTypeName
* Human-readable version of BlockingResourceType enum.
*/
static const char* const kResourceTypeName[];
#ifdef DEBUG
static size_t SizeOfDeadlockDetector(MallocSizeOf aMallocSizeOf);
/**
* Print
* Write a description of this blocking resource to |aOut|. 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.
*
* *NOT* thread safe. Reads |mAcquisitionContext| without
* synchronization, but this will not cause correctness
* problems.
*
* contexts into strings, all info is written to stderr, but
* only some info is written into |aOut|
*/
bool Print(nsACString& aOut) const;
size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const {
// NB: |mName| is not reported as it's expected to be a static string.
// If we switch to a nsString it should be added to the tally.
// |mChainPrev| is not reported because its memory is not owned.
size_t n = aMallocSizeOf(this);
return n;
}
// ``DDT'' = ``Deadlock Detector Type''
typedef DeadlockDetector<BlockingResourceBase> DDT;
protected:
# ifdef MOZ_CALLSTACK_DISABLED
typedef bool AcquisitionState;
# else
// Using maybe to use emplacement as the acquisition state flag; we may not
// always get a stack trace because of possible stack walk suppression or
// errors, hence can't use !IsEmpty() on the array itself as indication.
static size_t const kAcquisitionStateStackSize = 24;
typedef Maybe<AutoTArray<void*, kAcquisitionStateStackSize> >
AcquisitionState;
# endif
/**
* 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.
**/
void CheckAcquire();
/**
* Acquire
*
* *NOT* thread safe. Requires ownership of underlying resource.
**/
void Acquire(); // 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)
/**
* ResourceChainFront
*
* Thread safe.
*
* @return the front of the resource acquisition chain, i.e., the last
* resource acquired.
*/
static BlockingResourceBase* ResourceChainFront() {
return sResourceAcqnChainFront.get();
}
/**
* 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;
sResourceAcqnChainFront.set(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");
sResourceAcqnChainFront.set(mChainPrev);
} // NS_NEEDS_RESOURCE(this)
/**
* TakeAcquisitionState
* Return whether or not this resource was acquired and mark the resource
* as not acquired for subsequent uses.
*
* *NOT* thread safe. Requires ownership of underlying resource.
*/
AcquisitionState TakeAcquisitionState() {
# ifdef MOZ_CALLSTACK_DISABLED
bool acquired = mAcquired;
ClearAcquisitionState();
return acquired;
# else
return mAcquired.take();
# endif
}
/**
* SetAcquisitionState
* Set whether or not this resource was acquired.
*
* *NOT* thread safe. Requires ownership of underlying resource.
*/
void SetAcquisitionState(AcquisitionState&& aAcquisitionState) {
mAcquired = std::move(aAcquisitionState);
}
/**
* ClearAcquisitionState
* Indicate this resource is not acquired.
*
* *NOT* thread safe. Requires ownership of underlying resource.
*/
void ClearAcquisitionState() {
# ifdef MOZ_CALLSTACK_DISABLED
mAcquired = false;
# else
mAcquired.reset();
# endif
}
/**
* IsAcquired
* Indicates if this resource is acquired.
*
* *NOT* thread safe. Requires ownership of underlying resource.
*/
bool IsAcquired() const { return (bool)mAcquired; }
/**
* 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:
/**
* 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;
/**
* mAcquired
* Indicates if this resource is currently acquired.
*/
AcquisitionState mAcquired;
# ifndef MOZ_CALLSTACK_DISABLED
/**
* mFirstSeen
* Inidicates where this resource was first acquired.
*/
AcquisitionState mFirstSeen;
# endif
/**
* sCallOnce
* Ensures static members are initialized only once, and in a
* thread-safe way.
*/
static PRCallOnceType sCallOnce;
/**
* Thread-private pointer to the front of each thread's resource
* acquisition chain.
*/
static MOZ_THREAD_LOCAL(BlockingResourceBase*) sResourceAcqnChainFront;
/**
* 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();
/**
* Shutdown
* Free static members.
*
* *NOT* thread safe.
*/
static void Shutdown();
static void StackWalkCallback(uint32_t aFrameNumber, void* aPc, void* aSp,
void* aClosure);
static void GetStackTrace(AcquisitionState& aState,
const void* aFirstFramePC);
# 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