gecko-dev/tools/profiler/IOInterposer.cpp

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C++

/* 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/. */
#include <algorithm>
#include <vector>
#include "IOInterposer.h"
#include "mozilla/Mutex.h"
#include "mozilla/StaticPtr.h"
using namespace mozilla;
namespace {
/** Lists of Observers */
struct ObserverLists {
ObserverLists()
{
mObserverListsLock = PR_NewLock();
// We don't do MOZ_COUNT_CTOR(ObserverLists) as we will need to leak the
// IO interposer when doing late-write checks, which uses IO interposing
// to check for writes while static destructors are invoked.
}
// mObserverListsLock guards access to lists of observers
// Note, we can use mozilla::Mutex here as the ObserverLists may be leaked, as
// we want to monitor IO during shutdown. Furthermore, as we may have to
// unregister observers during shutdown an OffTheBooksMutex is not an option
// either, as it base calls into sDeadlockDetector which may be NULL during
// shutdown.
PRLock* mObserverListsLock;
~ObserverLists()
{
PR_DestroyLock(mObserverListsLock);
mObserverListsLock = nullptr;
}
// Lists of observers for read, write and fsync events respectively
// These are implemented as vectors since they are allowed to survive gecko,
// without reporting leaks. This is necessary for the IOInterposer to be used
// for late-write checks.
std::vector<IOInterposeObserver*> mCreateObservers;
std::vector<IOInterposeObserver*> mReadObservers;
std::vector<IOInterposeObserver*> mWriteObservers;
std::vector<IOInterposeObserver*> mFSyncObservers;
std::vector<IOInterposeObserver*> mStatObservers;
std::vector<IOInterposeObserver*> mCloseObservers;
};
/**
* A quick and dirty RAII class to automatically lock a PRLock
*/
class AutoPRLock
{
PRLock* mLock;
public:
AutoPRLock(PRLock* aLock)
: mLock(aLock)
{
PR_Lock(aLock);
}
~AutoPRLock()
{
PR_Unlock(mLock);
}
};
// List of observers registered
static StaticAutoPtr<ObserverLists> sObserverLists;
/** Find if a vector contains a specific element */
template<class T>
bool VectorContains(const std::vector<T>& vector, const T& element)
{
return std::find(vector.begin(), vector.end(), element) != vector.end();
}
/** Remove element from a vector */
template<class T>
void VectorRemove(std::vector<T>& vector, const T& element)
{
typename std::vector<T>::iterator newEnd = std::remove(vector.begin(),
vector.end(), element);
vector.erase(newEnd, vector.end());
}
} // anonymous namespace
// Flags tracking which operations are being observed
IOInterposeObserver::Operation IOInterposer::sObservedOperations =
IOInterposeObserver::OpNone;
/* static */ void IOInterposer::Init()
{
// Don't initialize twice...
if (sObserverLists) {
return;
}
sObserverLists = new ObserverLists();
sObservedOperations = IOInterposeObserver::OpNone;
}
/* static */ void IOInterposer::Clear()
{
// Clear() shouldn't be called if Init() wasn't called,
MOZ_ASSERT(sObserverLists);
if (sObserverLists) {
// We require everybody unregister before clearing. If somebody didn't then
// this is probably a case where one consumer clears the IO interposer and
// another consumer still wants events.
MOZ_ASSERT(sObserverLists->mReadObservers.empty());
MOZ_ASSERT(sObserverLists->mWriteObservers.empty());
MOZ_ASSERT(sObserverLists->mFSyncObservers.empty());
sObserverLists = nullptr;
sObservedOperations = IOInterposeObserver::OpNone;
}
}
/* static */ void IOInterposer::Report(
IOInterposeObserver::Observation& aObservation)
{
// IOInterposer::Init most be called before this method
MOZ_ASSERT(sObserverLists);
if (!sObserverLists) {
return;
}
//TODO: We only need read access here, so we should investigate the
// performance overhead involved in using some kind of shared lock.
// Work towards this end is tracked in bug #913653
AutoPRLock listLock(sObserverLists->mObserverListsLock);
// Don't try to report if there's nobody listening
if (!IOInterposer::IsObservedOperation(aObservation.ObservedOperation())) {
return;
}
// Decide which list of observers to inform
std::vector<IOInterposeObserver*>* observers = nullptr;
switch (aObservation.ObservedOperation()) {
case IOInterposeObserver::OpCreateOrOpen:
{
observers = &sObserverLists->mCreateObservers;
}
break;
case IOInterposeObserver::OpRead:
{
observers = &sObserverLists->mReadObservers;
}
break;
case IOInterposeObserver::OpWrite:
{
observers = &sObserverLists->mWriteObservers;
}
break;
case IOInterposeObserver::OpFSync:
{
observers = &sObserverLists->mFSyncObservers;
}
break;
case IOInterposeObserver::OpStat:
{
observers = &sObserverLists->mStatObservers;
}
break;
case IOInterposeObserver::OpClose:
{
observers = &sObserverLists->mCloseObservers;
}
break;
default:
{
// Invalid IO operation, see documentation comment for Report()
MOZ_ASSERT(false);
// Just ignore is in non-debug builds.
return;
}
}
MOZ_ASSERT(observers);
// Inform observers
uint32_t nObservers = observers->size();
for (uint32_t i = 0; i < nObservers; ++i) {
(*observers)[i]->Observe(aObservation);
}
}
/* static */ void IOInterposer::Register(IOInterposeObserver::Operation aOp,
IOInterposeObserver* aObserver)
{
// IOInterposer::Init most be called before this method
MOZ_ASSERT(sObserverLists);
// We should never register NULL as observer
MOZ_ASSERT(aObserver);
if (!sObserverLists || !aObserver) {
return;
}
AutoPRLock listLock(sObserverLists->mObserverListsLock);
// You can register to observe multiple types of observations
// but you'll never be registered twice for the same observations.
if (aOp & IOInterposeObserver::OpCreateOrOpen &&
!VectorContains(sObserverLists->mCreateObservers, aObserver)) {
sObserverLists->mCreateObservers.push_back(aObserver);
}
if (aOp & IOInterposeObserver::OpRead &&
!VectorContains(sObserverLists->mReadObservers, aObserver)) {
sObserverLists->mReadObservers.push_back(aObserver);
}
if (aOp & IOInterposeObserver::OpWrite &&
!VectorContains(sObserverLists->mWriteObservers, aObserver)) {
sObserverLists->mWriteObservers.push_back(aObserver);
}
if (aOp & IOInterposeObserver::OpFSync &&
!VectorContains(sObserverLists->mFSyncObservers, aObserver)) {
sObserverLists->mFSyncObservers.push_back(aObserver);
}
if (aOp & IOInterposeObserver::OpStat &&
!VectorContains(sObserverLists->mStatObservers, aObserver)) {
sObserverLists->mStatObservers.push_back(aObserver);
}
if (aOp & IOInterposeObserver::OpClose &&
!VectorContains(sObserverLists->mCloseObservers, aObserver)) {
sObserverLists->mCloseObservers.push_back(aObserver);
}
// Update field of observed operation with the operations that the new
// observer is observing.
sObservedOperations = (IOInterposeObserver::Operation)
(sObservedOperations | aOp);
}
/* static */ void IOInterposer::Unregister(IOInterposeObserver::Operation aOp,
IOInterposeObserver* aObserver)
{
// IOInterposer::Init most be called before this method.
MOZ_ASSERT(sObserverLists);
if (!sObserverLists) {
return;
}
AutoPRLock listLock(sObserverLists->mObserverListsLock);
if (aOp & IOInterposeObserver::OpRead) {
VectorRemove(sObserverLists->mReadObservers, aObserver);
if (sObserverLists->mReadObservers.empty()) {
sObservedOperations = (IOInterposeObserver::Operation)
(sObservedOperations & ~IOInterposeObserver::OpRead);
}
}
if (aOp & IOInterposeObserver::OpWrite) {
VectorRemove(sObserverLists->mWriteObservers, aObserver);
if (sObserverLists->mWriteObservers.empty()) {
sObservedOperations = (IOInterposeObserver::Operation)
(sObservedOperations & ~IOInterposeObserver::OpWrite);
}
}
if (aOp & IOInterposeObserver::OpFSync) {
VectorRemove(sObserverLists->mFSyncObservers, aObserver);
if (sObserverLists->mFSyncObservers.empty()) {
sObservedOperations = (IOInterposeObserver::Operation)
(sObservedOperations & ~IOInterposeObserver::OpFSync);
}
}
}