js/xpconnect/src/XPCMaps.cpp
author Kyle Huey <khuey@kylehuey.com>
Tue, 11 Aug 2015 06:10:46 -0700
changeset 257246 a13c1f26e351dd6251da641fe7a9eb53790fc2d0
parent 255586 525bb2034be22ff987ddc87cfeff8407ea2689e5
child 262708 16597175b6f3678f38020fdf4c4a7f4debf38d2e
permissions -rw-r--r--
Bug 1179909: Refactor stable state handling. r=smaug This is motivated by three separate but related problems: 1. Our concept of recursion depth is broken for things that run from AfterProcessNextEvent observers (e.g. Promises). We decrement the recursionDepth counter before firing observers, so a Promise callback running at the lowest event loop depth has a recursion depth of 0 (whereas a regular nsIRunnable would be 1). This is a problem because it's impossible to distinguish a Promise running after a sync XHR's onreadystatechange handler from a top-level event (since the former runs with depth 2 - 1 = 1, and the latter runs with just 1). 2. The nsIThreadObserver mechanism that is used by a lot of code to run "after" the current event is a poor fit for anything that runs script. First, the order the observers fire in is the order they were added, not anything fixed by spec. Additionally, running script can cause the event loop to spin, which is a big source of pain here (bholley has some nasty bug caused by this). 3. We run Promises from different points in the code for workers and main thread. The latter runs from XPConnect's nsIThreadObserver callbacks, while the former runs from a hardcoded call to run Promises in the worker event loop. What workers do is particularly problematic because it means we can't get the right recursion depth no matter what we do to nsThread. The solve this, this patch does the following: 1. Consolidate some handling of microtasks and all handling of stable state from appshell and WorkerPrivate into CycleCollectedJSRuntime. 2. Make the recursionDepth counter only available to CycleCollectedJSRuntime (and its consumers) and remove it from the nsIThreadInternal and nsIThreadObserver APIs. 3. Adjust the recursionDepth counter so that microtasks run with the recursionDepth of the task they are associated with. 4. Introduce the concept of metastable state to replace appshell's RunBeforeNextEvent. Metastable state is reached after every microtask or task is completed. This provides the semantics that bent and I want for IndexedDB, where transactions autocommit at the end of a microtask and do not "spill" from one microtask into a subsequent microtask. This differs from appshell's RunBeforeNextEvent in two ways: a) It fires between microtasks, which was the motivation for starting this. b) It no longer ensures that we're at the same event loop depth in the native event queue. bent decided we don't care about this. 5. Reorder stable state to happen after microtasks such as Promises, per HTML. Right now we call the regular thread observers, including appshell, before the main thread observer (XPConnect), so stable state tasks happen before microtasks.

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=99: */
/* 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/. */

/* Private maps (hashtables). */

#include "mozilla/MathAlgorithms.h"
#include "mozilla/MemoryReporting.h"
#include "xpcprivate.h"

#include "js/HashTable.h"

using namespace mozilla;

/***************************************************************************/
// static shared...

// Note this is returning the bit pattern of the first part of the nsID, not
// the pointer to the nsID.

static PLDHashNumber
HashIIDPtrKey(PLDHashTable* table, const void* key)
{
    return *((js::HashNumber*)key);
}

static bool
MatchIIDPtrKey(PLDHashTable* table,
               const PLDHashEntryHdr* entry,
               const void* key)
{
    return ((const nsID*)key)->
                Equals(*((const nsID*)((PLDHashEntryStub*)entry)->key));
}

static PLDHashNumber
HashNativeKey(PLDHashTable* table, const void* key)
{
    XPCNativeSetKey* Key = (XPCNativeSetKey*) key;

    PLDHashNumber h = 0;

    XPCNativeSet*       Set;
    XPCNativeInterface* Addition;
    uint16_t            Position;

    if (Key->IsAKey()) {
        Set      = Key->GetBaseSet();
        Addition = Key->GetAddition();
        Position = Key->GetPosition();
    } else {
        Set      = (XPCNativeSet*) Key;
        Addition = nullptr;
        Position = 0;
    }

    if (!Set) {
        MOZ_ASSERT(Addition, "bad key");
        // This would be an XOR like below.
        // But "0 ^ x == x". So it does not matter.
        h = (js::HashNumber) NS_PTR_TO_INT32(Addition) >> 2;
    } else {
        XPCNativeInterface** Current = Set->GetInterfaceArray();
        uint16_t count = Set->GetInterfaceCount();
        if (Addition) {
            count++;
            for (uint16_t i = 0; i < count; i++) {
                if (i == Position)
                    h ^= (js::HashNumber) NS_PTR_TO_INT32(Addition) >> 2;
                else
                    h ^= (js::HashNumber) NS_PTR_TO_INT32(*(Current++)) >> 2;
            }
        } else {
            for (uint16_t i = 0; i < count; i++)
                h ^= (js::HashNumber) NS_PTR_TO_INT32(*(Current++)) >> 2;
        }
    }

    return h;
}

/***************************************************************************/
// implement JSObject2WrappedJSMap...

void
JSObject2WrappedJSMap::UpdateWeakPointersAfterGC(XPCJSRuntime* runtime)
{
    // Check all wrappers and update their JSObject pointer if it has been
    // moved, or if it is about to be finalized queue the wrapper for
    // destruction by adding it to an array held by the runtime.
    // Note that we do not want to be changing the refcount of these wrappers.
    // We add them to the array now and Release the array members later to avoid
    // the posibility of doing any JS GCThing allocations during the gc cycle.

    nsTArray<nsXPCWrappedJS*>& dying = runtime->WrappedJSToReleaseArray();
    MOZ_ASSERT(dying.IsEmpty());

    for (Map::Enum e(mTable); !e.empty(); e.popFront()) {
        nsXPCWrappedJS* wrapper = e.front().value();
        MOZ_ASSERT(wrapper, "found a null JS wrapper!");

        // Walk the wrapper chain and update all JSObjects.
        while (wrapper) {
#ifdef DEBUG
            if (!wrapper->IsSubjectToFinalization()) {
                // If a wrapper is not subject to finalization then it roots its
                // JS object.  If so, then it will not be about to be finalized
                // and any necessary pointer update will have already happened
                // when it was marked.
                JSObject* obj = wrapper->GetJSObjectPreserveColor();
                JSObject* prior = obj;
                JS_UpdateWeakPointerAfterGCUnbarriered(&obj);
                MOZ_ASSERT(obj == prior);
            }
#endif
            if (wrapper->IsSubjectToFinalization()) {
                wrapper->UpdateObjectPointerAfterGC();
                if (!wrapper->GetJSObjectPreserveColor())
                    dying.AppendElement(wrapper);
            }
            wrapper = wrapper->GetNextWrapper();
        }

        // Remove or update the JSObject key in the table if necessary.
        JSObject* obj = e.front().key();
        JSObject* prior = obj;
        JS_UpdateWeakPointerAfterGCUnbarriered(&obj);
        if (!obj)
            e.removeFront();
        else if (obj != prior)
            e.rekeyFront(obj);
    }
}

void
JSObject2WrappedJSMap::ShutdownMarker()
{
    for (Map::Range r = mTable.all(); !r.empty(); r.popFront()) {
        nsXPCWrappedJS* wrapper = r.front().value();
        MOZ_ASSERT(wrapper, "found a null JS wrapper!");
        MOZ_ASSERT(wrapper->IsValid(), "found an invalid JS wrapper!");
        wrapper->SystemIsBeingShutDown();
    }
}

size_t
JSObject2WrappedJSMap::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = mallocSizeOf(this);
    n += mTable.sizeOfExcludingThis(mallocSizeOf);
    return n;
}

size_t
JSObject2WrappedJSMap::SizeOfWrappedJS(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = 0;
    for (Map::Range r = mTable.all(); !r.empty(); r.popFront())
        n += r.front().value()->SizeOfIncludingThis(mallocSizeOf);
    return n;
}

/***************************************************************************/
// implement Native2WrappedNativeMap...

// static
Native2WrappedNativeMap*
Native2WrappedNativeMap::newMap(int length)
{
    return new Native2WrappedNativeMap(length);
}

Native2WrappedNativeMap::Native2WrappedNativeMap(int length)
  : mTable(new PLDHashTable(PL_DHashGetStubOps(), sizeof(Entry), length))
{
}

Native2WrappedNativeMap::~Native2WrappedNativeMap()
{
    delete mTable;
}

size_t
Native2WrappedNativeMap::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = mallocSizeOf(this);
    n += mTable->ShallowSizeOfIncludingThis(mallocSizeOf);
    for (auto iter = mTable->Iter(); !iter.Done(); iter.Next()) {
        auto entry = static_cast<Native2WrappedNativeMap::Entry*>(iter.Get());
        n += mallocSizeOf(entry->value);
    }
    return n;
}

/***************************************************************************/
// implement IID2WrappedJSClassMap...

const struct PLDHashTableOps IID2WrappedJSClassMap::Entry::sOps =
{
    HashIIDPtrKey,
    MatchIIDPtrKey,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub
};

// static
IID2WrappedJSClassMap*
IID2WrappedJSClassMap::newMap(int length)
{
    return new IID2WrappedJSClassMap(length);
}

IID2WrappedJSClassMap::IID2WrappedJSClassMap(int length)
  : mTable(new PLDHashTable(&Entry::sOps, sizeof(Entry), length))
{
}

IID2WrappedJSClassMap::~IID2WrappedJSClassMap()
{
    delete mTable;
}

/***************************************************************************/
// implement IID2NativeInterfaceMap...

const struct PLDHashTableOps IID2NativeInterfaceMap::Entry::sOps =
{
    HashIIDPtrKey,
    MatchIIDPtrKey,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub
};

// static
IID2NativeInterfaceMap*
IID2NativeInterfaceMap::newMap(int length)
{
    return new IID2NativeInterfaceMap(length);
}

IID2NativeInterfaceMap::IID2NativeInterfaceMap(int length)
  : mTable(new PLDHashTable(&Entry::sOps, sizeof(Entry), length))
{
}

IID2NativeInterfaceMap::~IID2NativeInterfaceMap()
{
    delete mTable;
}

size_t
IID2NativeInterfaceMap::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = mallocSizeOf(this);
    n += mTable->ShallowSizeOfIncludingThis(mallocSizeOf);
    for (auto iter = mTable->Iter(); !iter.Done(); iter.Next()) {
        auto entry = static_cast<IID2NativeInterfaceMap::Entry*>(iter.Get());
        n += entry->value->SizeOfIncludingThis(mallocSizeOf);
    }
    return n;
}

/***************************************************************************/
// implement ClassInfo2NativeSetMap...

// static
ClassInfo2NativeSetMap*
ClassInfo2NativeSetMap::newMap(int length)
{
    return new ClassInfo2NativeSetMap(length);
}

ClassInfo2NativeSetMap::ClassInfo2NativeSetMap(int length)
  : mTable(new PLDHashTable(PL_DHashGetStubOps(), sizeof(Entry), length))
{
}

ClassInfo2NativeSetMap::~ClassInfo2NativeSetMap()
{
    delete mTable;
}

size_t
ClassInfo2NativeSetMap::ShallowSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf)
{
    size_t n = mallocSizeOf(this);
    n += mTable->ShallowSizeOfIncludingThis(mallocSizeOf);
    return n;
}

/***************************************************************************/
// implement ClassInfo2WrappedNativeProtoMap...

// static
ClassInfo2WrappedNativeProtoMap*
ClassInfo2WrappedNativeProtoMap::newMap(int length)
{
    return new ClassInfo2WrappedNativeProtoMap(length);
}

ClassInfo2WrappedNativeProtoMap::ClassInfo2WrappedNativeProtoMap(int length)
  : mTable(new PLDHashTable(PL_DHashGetStubOps(), sizeof(Entry), length))
{
}

ClassInfo2WrappedNativeProtoMap::~ClassInfo2WrappedNativeProtoMap()
{
    delete mTable;
}

size_t
ClassInfo2WrappedNativeProtoMap::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = mallocSizeOf(this);
    n += mTable->ShallowSizeOfIncludingThis(mallocSizeOf);
    for (auto iter = mTable->Iter(); !iter.Done(); iter.Next()) {
        auto entry = static_cast<ClassInfo2WrappedNativeProtoMap::Entry*>(iter.Get());
        n += mallocSizeOf(entry->value);
    }
    return n;
}

/***************************************************************************/
// implement NativeSetMap...

bool
NativeSetMap::Entry::Match(PLDHashTable* table,
                           const PLDHashEntryHdr* entry,
                           const void* key)
{
    XPCNativeSetKey* Key = (XPCNativeSetKey*) key;

    // See the comment in the XPCNativeSetKey declaration in xpcprivate.h.
    if (!Key->IsAKey()) {
        XPCNativeSet* Set1 = (XPCNativeSet*) key;
        XPCNativeSet* Set2 = ((Entry*)entry)->key_value;

        if (Set1 == Set2)
            return true;

        uint16_t count = Set1->GetInterfaceCount();
        if (count != Set2->GetInterfaceCount())
            return false;

        XPCNativeInterface** Current1 = Set1->GetInterfaceArray();
        XPCNativeInterface** Current2 = Set2->GetInterfaceArray();
        for (uint16_t i = 0; i < count; i++) {
            if (*(Current1++) != *(Current2++))
                return false;
        }

        return true;
    }

    XPCNativeSet*       SetInTable = ((Entry*)entry)->key_value;
    XPCNativeSet*       Set        = Key->GetBaseSet();
    XPCNativeInterface* Addition   = Key->GetAddition();

    if (!Set) {
        // This is a special case to deal with the invariant that says:
        // "All sets have exactly one nsISupports interface and it comes first."
        // See XPCNativeSet::NewInstance for details.
        //
        // Though we might have a key that represents only one interface, we
        // know that if that one interface were contructed into a set then
        // it would end up really being a set with two interfaces (except for
        // the case where the one interface happened to be nsISupports).

        return (SetInTable->GetInterfaceCount() == 1 &&
                SetInTable->GetInterfaceAt(0) == Addition) ||
               (SetInTable->GetInterfaceCount() == 2 &&
                SetInTable->GetInterfaceAt(1) == Addition);
    }

    if (!Addition && Set == SetInTable)
        return true;

    uint16_t count = Set->GetInterfaceCount() + (Addition ? 1 : 0);
    if (count != SetInTable->GetInterfaceCount())
        return false;

    uint16_t Position = Key->GetPosition();
    XPCNativeInterface** CurrentInTable = SetInTable->GetInterfaceArray();
    XPCNativeInterface** Current = Set->GetInterfaceArray();
    for (uint16_t i = 0; i < count; i++) {
        if (Addition && i == Position) {
            if (Addition != *(CurrentInTable++))
                return false;
        } else {
            if (*(Current++) != *(CurrentInTable++))
                return false;
        }
    }

    return true;
}

const struct PLDHashTableOps NativeSetMap::Entry::sOps =
{
    HashNativeKey,
    Match,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub
};

// static
NativeSetMap*
NativeSetMap::newMap(int length)
{
    return new NativeSetMap(length);
}

NativeSetMap::NativeSetMap(int length)
  : mTable(new PLDHashTable(&Entry::sOps, sizeof(Entry), length))
{
}

NativeSetMap::~NativeSetMap()
{
    delete mTable;
}

size_t
NativeSetMap::SizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const
{
    size_t n = mallocSizeOf(this);
    n += mTable->ShallowSizeOfIncludingThis(mallocSizeOf);
    for (auto iter = mTable->Iter(); !iter.Done(); iter.Next()) {
        auto entry = static_cast<NativeSetMap::Entry*>(iter.Get());
        n += entry->key_value->SizeOfIncludingThis(mallocSizeOf);
    }
    return n;
}

/***************************************************************************/
// implement IID2ThisTranslatorMap...

bool
IID2ThisTranslatorMap::Entry::Match(PLDHashTable* table,
                                    const PLDHashEntryHdr* entry,
                                    const void* key)
{
    return ((const nsID*)key)->Equals(((Entry*)entry)->key);
}

void
IID2ThisTranslatorMap::Entry::Clear(PLDHashTable* table, PLDHashEntryHdr* entry)
{
    static_cast<Entry*>(entry)->value = nullptr;
    memset(entry, 0, table->EntrySize());
}

const struct PLDHashTableOps IID2ThisTranslatorMap::Entry::sOps =
{
    HashIIDPtrKey,
    Match,
    PL_DHashMoveEntryStub,
    Clear
};

// static
IID2ThisTranslatorMap*
IID2ThisTranslatorMap::newMap(int length)
{
    return new IID2ThisTranslatorMap(length);
}

IID2ThisTranslatorMap::IID2ThisTranslatorMap(int length)
  : mTable(new PLDHashTable(&Entry::sOps, sizeof(Entry), length))
{
}

IID2ThisTranslatorMap::~IID2ThisTranslatorMap()
{
    delete mTable;
}

/***************************************************************************/

PLDHashNumber
XPCNativeScriptableSharedMap::Entry::Hash(PLDHashTable* table, const void* key)
{
    PLDHashNumber h;
    const unsigned char* s;

    XPCNativeScriptableShared* obj =
        (XPCNativeScriptableShared*) key;

    // hash together the flags and the classname string, ignore the interfaces
    // bitmap since it's very rare that it's different when flags and classname
    // are the same.

    h = (PLDHashNumber) obj->GetFlags();
    for (s = (const unsigned char*) obj->GetJSClass()->name; *s != '\0'; s++)
        h = RotateLeft(h, 4) ^ *s;
    return h;
}

bool
XPCNativeScriptableSharedMap::Entry::Match(PLDHashTable* table,
                                           const PLDHashEntryHdr* entry,
                                           const void* key)
{
    XPCNativeScriptableShared* obj1 =
        ((XPCNativeScriptableSharedMap::Entry*) entry)->key;

    XPCNativeScriptableShared* obj2 =
        (XPCNativeScriptableShared*) key;

    // match the flags and the classname string

    if (obj1->GetFlags() != obj2->GetFlags())
        return false;

    const char* name1 = obj1->GetJSClass()->name;
    const char* name2 = obj2->GetJSClass()->name;

    if (!name1 || !name2)
        return name1 == name2;

    return 0 == strcmp(name1, name2);
}

const struct PLDHashTableOps XPCNativeScriptableSharedMap::Entry::sOps =
{
    Hash,
    Match,
    PL_DHashMoveEntryStub,
    PL_DHashClearEntryStub
};

// static
XPCNativeScriptableSharedMap*
XPCNativeScriptableSharedMap::newMap(int length)
{
    return new XPCNativeScriptableSharedMap(length);
}

XPCNativeScriptableSharedMap::XPCNativeScriptableSharedMap(int length)
  : mTable(new PLDHashTable(&Entry::sOps, sizeof(Entry), length))
{
}

XPCNativeScriptableSharedMap::~XPCNativeScriptableSharedMap()
{
    delete mTable;
}

bool
XPCNativeScriptableSharedMap::GetNewOrUsed(uint32_t flags,
                                           char* name,
                                           XPCNativeScriptableInfo* si)
{
    NS_PRECONDITION(name,"bad param");
    NS_PRECONDITION(si,"bad param");

    XPCNativeScriptableShared key(flags, name);
    Entry* entry = static_cast<Entry*>
        (PL_DHashTableAdd(mTable, &key, fallible));
    if (!entry)
        return false;

    XPCNativeScriptableShared* shared = entry->key;

    if (!shared) {
        entry->key = shared =
            new XPCNativeScriptableShared(flags, key.TransferNameOwnership());
        if (!shared)
            return false;
        shared->PopulateJSClass();
    }
    si->SetScriptableShared(shared);
    return true;
}

/***************************************************************************/
// implement XPCWrappedNativeProtoMap...

// static
XPCWrappedNativeProtoMap*
XPCWrappedNativeProtoMap::newMap(int length)
{
    return new XPCWrappedNativeProtoMap(length);
}

XPCWrappedNativeProtoMap::XPCWrappedNativeProtoMap(int length)
  : mTable(new PLDHashTable(PL_DHashGetStubOps(), sizeof(PLDHashEntryStub),
                            length))
{
}

XPCWrappedNativeProtoMap::~XPCWrappedNativeProtoMap()
{
    delete mTable;
}

/***************************************************************************/