nsObserverService.cpp

/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* 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 "prlog.h"
#include "nsAutoPtr.h"
#include "nsIObserverService.h"
#include "nsIObserver.h"
#include "nsObserverService.h"
#include "nsObserverList.h"
#include "nsThreadUtils.h"
#include "nsEnumeratorUtils.h"
#include "mozilla/net/NeckoCommon.h"
#include "mozilla/Services.h"

#define NOTIFY_GLOBAL_OBSERVERS

#if defined(PR_LOGGING)
// Log module for nsObserverService logging...
//
// To enable logging (see prlog.h for full details):
//
//    set NSPR_LOG_MODULES=ObserverService:5
//    set NSPR_LOG_FILE=nspr.log
//
// this enables PR_LOG_DEBUG level information and places all output in
// the file nspr.log
static PRLogModuleInfo*
GetObserverServiceLog()
{
    static PRLogModuleInfo *sLog;
    if (!sLog)
        sLog = PR_NewLogModule("ObserverService");
    return sLog;
}
  #define LOG(x)  PR_LOG(GetObserverServiceLog(), PR_LOG_DEBUG, x)
#else
  #define LOG(x)
#endif /* PR_LOGGING */

namespace mozilla {

struct SuspectObserver {
    SuspectObserver(const char* aTopic, size_t aReferentCount)
        : topic(aTopic), referentCount(aReferentCount) {}
    const char* topic;
    size_t referentCount;
};

struct ObserverServiceReferentCount {
    ObserverServiceReferentCount()
        : numStrong(0), numWeakAlive(0), numWeakDead(0) {}
    size_t numStrong;
    size_t numWeakAlive;
    size_t numWeakDead;
    nsTArray<SuspectObserver> suspectObservers;
};

} // namespace mozilla

using namespace mozilla;

PLDHashOperator
nsObserverService::CountReferents(nsObserverList* aObserverList,
                                  void* aClosure)
{
    if (!aObserverList) {
        return PL_DHASH_NEXT;
    }

    ObserverServiceReferentCount* referentCount =
        static_cast<ObserverServiceReferentCount*>(aClosure);

    size_t numStrong = 0;
    size_t numWeakAlive = 0;
    size_t numWeakDead = 0;

    nsTArray<ObserverRef>& observers = aObserverList->mObservers;
    for (uint32_t i = 0; i < observers.Length(); i++) {
        if (observers[i].isWeakRef) {
            nsCOMPtr<nsIObserver> observerRef(
                do_QueryReferent(observers[i].asWeak()));
            if (observerRef) {
                numWeakAlive++;
            } else {
                numWeakDead++;
            }
        } else {
            numStrong++;
        }
    }

    referentCount->numStrong += numStrong;
    referentCount->numWeakAlive += numWeakAlive;
    referentCount->numWeakDead += numWeakDead;

    // Keep track of topics that have a suspiciously large number
    // of referents (symptom of leaks).
    size_t total = numStrong + numWeakAlive + numWeakDead;
    if (total > kSuspectReferentCount) {
        SuspectObserver suspect(aObserverList->GetKey(), total);
        referentCount->suspectObservers.AppendElement(suspect);
    }

    return PL_DHASH_NEXT;
}

NS_IMETHODIMP
nsObserverService::CollectReports(nsIHandleReportCallback* aHandleReport,
                                  nsISupports* aData, bool aAnonymize)
{
    ObserverServiceReferentCount referentCount;
    mObserverTopicTable.EnumerateEntries(CountReferents, &referentCount);

    // These aren't privacy-sensitive and so don't need anonymizing.
    nsresult rv;
    for (uint32_t i = 0; i < referentCount.suspectObservers.Length(); i++) {
        SuspectObserver& suspect = referentCount.suspectObservers[i];
        nsPrintfCString suspectPath("observer-service-suspect/"
                                    "referent(topic=%s)",
                                    suspect.topic);
        rv = aHandleReport->Callback(/* process */ EmptyCString(),
            suspectPath, KIND_OTHER, UNITS_COUNT, suspect.referentCount,
            NS_LITERAL_CSTRING("A topic with a suspiciously large number of "
                               "referents.  This may be symptomatic of a leak "
                               "if the number of referents is high with "
                               "respect to the number of windows."),
            aData);

      if (NS_WARN_IF(NS_FAILED(rv)))
          return rv;
    }

    rv = aHandleReport->Callback(/* process */ EmptyCString(),
        NS_LITERAL_CSTRING("observer-service/referent/strong"),
        KIND_OTHER, UNITS_COUNT, referentCount.numStrong,
        NS_LITERAL_CSTRING("The number of strong references held by the "
                           "observer service."),
        aData);

    if (NS_WARN_IF(NS_FAILED(rv)))
        return rv;

    rv = aHandleReport->Callback(/* process */ EmptyCString(),
        NS_LITERAL_CSTRING("observer-service/referent/weak/alive"),
        KIND_OTHER, UNITS_COUNT, referentCount.numWeakAlive,
        NS_LITERAL_CSTRING("The number of weak references held by the "
                           "observer service that are still alive."),
        aData);

    if (NS_WARN_IF(NS_FAILED(rv)))
        return rv;

    rv = aHandleReport->Callback(/* process */ EmptyCString(),
        NS_LITERAL_CSTRING("observer-service/referent/weak/dead"),
        KIND_OTHER, UNITS_COUNT, referentCount.numWeakDead,
        NS_LITERAL_CSTRING("The number of weak references held by the "
                           "observer service that are dead."),
        aData);

    if (NS_WARN_IF(NS_FAILED(rv)))
        return rv;

    return NS_OK;
}

////////////////////////////////////////////////////////////////////////////////
// nsObserverService Implementation


NS_IMPL_ISUPPORTS(
    nsObserverService,
    nsIObserverService,
    nsObserverService,
    nsIMemoryReporter)

nsObserverService::nsObserverService() :
    mShuttingDown(false)
{
}

nsObserverService::~nsObserverService(void)
{
    Shutdown();
}

void
nsObserverService::RegisterReporter()
{
    RegisterWeakMemoryReporter(this);
}

void
nsObserverService::Shutdown()
{
    UnregisterWeakMemoryReporter(this);

    mShuttingDown = true;

    mObserverTopicTable.Clear();
}

nsresult
nsObserverService::Create(nsISupports* outer, const nsIID& aIID, void* *aInstancePtr)
{
    LOG(("nsObserverService::Create()"));

    nsRefPtr<nsObserverService> os = new nsObserverService();

    if (!os)
        return NS_ERROR_OUT_OF_MEMORY;

    // The memory reporter can not be immediately registered here because
    // the nsMemoryReporterManager may attempt to get the nsObserverService
    // during initialization, causing a recursive GetService.
    nsRefPtr<nsRunnableMethod<nsObserverService> > registerRunnable =
        NS_NewRunnableMethod(os, &nsObserverService::RegisterReporter);
    NS_DispatchToCurrentThread(registerRunnable);

    return os->QueryInterface(aIID, aInstancePtr);
}

#define NS_ENSURE_VALIDCALL \
    if (!NS_IsMainThread()) {                                     \
        MOZ_CRASH("Using observer service off the main thread!"); \
        return NS_ERROR_UNEXPECTED;                               \
    }                                                             \
    if (mShuttingDown) {                                          \
        NS_ERROR("Using observer service after XPCOM shutdown!"); \
        return NS_ERROR_ILLEGAL_DURING_SHUTDOWN;                  \
    }

NS_IMETHODIMP
nsObserverService::AddObserver(nsIObserver* anObserver, const char* aTopic,
                               bool ownsWeak)
{
    LOG(("nsObserverService::AddObserver(%p: %s)",
         (void*) anObserver, aTopic));

    NS_ENSURE_VALIDCALL
    if (NS_WARN_IF(!anObserver) || NS_WARN_IF(!aTopic))
        return NS_ERROR_INVALID_ARG;

    if (mozilla::net::IsNeckoChild() && !strncmp(aTopic, "http-on-", 8)) {
      return NS_ERROR_NOT_IMPLEMENTED;
    }

    nsObserverList *observerList = mObserverTopicTable.PutEntry(aTopic);
    if (!observerList)
        return NS_ERROR_OUT_OF_MEMORY;

    return observerList->AddObserver(anObserver, ownsWeak);
}

NS_IMETHODIMP
nsObserverService::RemoveObserver(nsIObserver* anObserver, const char* aTopic)
{
    LOG(("nsObserverService::RemoveObserver(%p: %s)",
         (void*) anObserver, aTopic));
    NS_ENSURE_VALIDCALL
    if (NS_WARN_IF(!anObserver) || NS_WARN_IF(!aTopic))
        return NS_ERROR_INVALID_ARG;

    nsObserverList *observerList = mObserverTopicTable.GetEntry(aTopic);
    if (!observerList)
        return NS_ERROR_FAILURE;

    /* This death grip is to protect against stupid consumers who call
       RemoveObserver from their Destructor, see bug 485834/bug 325392. */
    nsCOMPtr<nsIObserver> kungFuDeathGrip(anObserver);
    return observerList->RemoveObserver(anObserver);
}

NS_IMETHODIMP
nsObserverService::EnumerateObservers(const char* aTopic,
                                      nsISimpleEnumerator** anEnumerator)
{
    NS_ENSURE_VALIDCALL
    if (NS_WARN_IF(!anEnumerator) || NS_WARN_IF(!aTopic))
        return NS_ERROR_INVALID_ARG;

    nsObserverList *observerList = mObserverTopicTable.GetEntry(aTopic);
    if (!observerList)
        return NS_NewEmptyEnumerator(anEnumerator);

    return observerList->GetObserverList(anEnumerator);
}

// Enumerate observers of aTopic and call Observe on each.
NS_IMETHODIMP nsObserverService::NotifyObservers(nsISupports *aSubject,
                                                 const char *aTopic,
                                                 const char16_t *someData)
{
    LOG(("nsObserverService::NotifyObservers(%s)", aTopic));

    NS_ENSURE_VALIDCALL
    if (NS_WARN_IF(!aTopic))
        return NS_ERROR_INVALID_ARG;

    nsObserverList *observerList = mObserverTopicTable.GetEntry(aTopic);
    if (observerList)
        observerList->NotifyObservers(aSubject, aTopic, someData);

#ifdef NOTIFY_GLOBAL_OBSERVERS
    observerList = mObserverTopicTable.GetEntry("*");
    if (observerList)
        observerList->NotifyObservers(aSubject, aTopic, someData);
#endif

    return NS_OK;
}

static PLDHashOperator
UnmarkGrayObserverEntry(nsObserverList* aObserverList, void* aClosure)
{
    if (aObserverList) {
        aObserverList->UnmarkGrayStrongObservers();
    }
    return PL_DHASH_NEXT;
}

NS_IMETHODIMP
nsObserverService::UnmarkGrayStrongObservers()
{
    NS_ENSURE_VALIDCALL

    mObserverTopicTable.EnumerateEntries(UnmarkGrayObserverEntry, nullptr);

    return NS_OK;
}