Debug Mode causes Assertion failures for Preference Access

[leeN]

It seems like we access preferences from more than one thread? If I compile in debug mode and run the mochitests I get the following crash:

0:18.31 GECKO(1158803) [1158803] Assertion failure: sInServoTraversal || NS_IsMainThread(), at /home/leen/project-foxhound/obj-tf-release/dist/include/mozilla/ServoUtils.h:33
Initializing stack-fixing for the first stack frame, this may take a while...
0:20.85 INFO runtests.py | Waiting for browser...
0:38.87 GECKO(1158803) #1: mozilla::IsInServoTraversal() (/home/leen/project-foxhound/obj-tf-release/dist/include/mozilla/ServoUtils.h:33)
0:38.87 GECKO(1158803) #2: mozilla::ServoStyleSet::IsInServoTraversal() (/home/leen/project-foxhound/obj-tf-release/dist/include/mozilla/ServoStyleSet.h:117)
0:38.87 GECKO(1158803) #3: mozilla::Preferences::InitStaticMembers() (/home/leen/project-foxhound/modules/libpref/Preferences.cpp:3755)
0:38.88 GECKO(1158803) #4: nsresult mozilla::Internals::GetPrefValue<bool*>(char const*, bool*&&, mozilla::PrefValueKind) (/home/leen/project-foxhound/modules/libpref/Preferences.cpp:4777)
0:38.89 GECKO(1158803) #5: bool mozilla::Internals::GetPref(char const*, bool, mozilla::PrefValueKind) (/home/leen/project-foxhound/modules/libpref/Preferences.cpp:4819)
0:38.90 GECKO(1158803) #6: mozilla::Preferences::GetBool(char const*, bool, mozilla::PrefValueKind) (/home/leen/project-foxhound/modules/libpref/Preferences.cpp:5207)
0:38.90 GECKO(1158803) #7: isActive(char const*) (/home/leen/project-foxhound/dom/tainting/nsTaintingUtils.cpp:37)
0:38.90 GECKO(1158803) #8: isSourceActive(char const*) (/home/leen/project-foxhound/dom/tainting/nsTaintingUtils.cpp:49)
0:38.91 GECKO(1158803) #9: MarkTaintSource(JSContext*, JS::MutableHandleJS::Value, char const*, nsTSubstring<char16_t> const&) (/home/leen/project-foxhound/dom/tainting/nsTaintingUtils.cpp:320)
0:38.92 GECKO(1158803) #10: mozilla::dom::MessageEvent::GetData(JSContext*, JS::MutableHandleJS::Value, mozilla::ErrorResult&) (/home/leen/project-foxhound/dom/events/MessageEvent.cpp:73)
0:38.92 GECKO(1158803) #11: mozilla::dom::MessageEvent_Binding::get_data(JSContext*, JS::Handle<JSObject*>, void*, JSJitGetterCallArgs) (MessageEventBinding.cpp:761)
0:38.92 GECKO(1158803) #12: bool mozilla::dom::binding_detail::GenericGetter<mozilla::dom::binding_detail::NormalThisPolicy, mozilla::dom::binding_detail::ThrowExceptions>(JSContext*, unsigned int, JS::Value*) (/home/leen/project-foxhound/dom/bindings/BindingUtils.cpp:3153)
0:38.92 GECKO(1158803) #13: CallJSNative(JSContext*, bool ()(JSContext, unsigned int, JS::Value*), js::CallReason, JS::CallArgs const&) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:494)
0:38.92 GECKO(1158803) #14: js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:592)
0:38.92 GECKO(1158803) #15: InternalCall(JSContext*, js::AnyInvokeArgs const&, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:659)
0:38.92 GECKO(1158803) #16: js::Call(JSContext*, JS::HandleJS::Value, JS::HandleJS::Value, js::AnyInvokeArgs const&, JS::MutableHandleJS::Value, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:691)
0:38.92 GECKO(1158803) #17: js::CallGetter(JSContext*, JS::HandleJS::Value, JS::HandleJS::Value, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:813)
0:38.92 GECKO(1158803) #18: CallGetter(JSContext*, JS::Handlejs::NativeObject*, JS::HandleJS::Value, JS::HandleJS::PropertyKey, js::PropertyInfoBase, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/NativeObject.cpp:2143)
0:38.92 GECKO(1158803) #19: bool GetExistingProperty<(js::AllowGC)1>(JSContext*, js::MaybeRooted<JS::Value, (js::AllowGC)1>::HandleType, js::MaybeRooted<js::NativeObject*, (js::AllowGC)1>::HandleType, js::MaybeRooted<JS::PropertyKey, (js::AllowGC)1>::HandleType, js::PropertyInfoBase, js::MaybeRooted<JS::Value, (js::AllowGC)1>::MutableHandleType) (/home/leen/project-foxhound/js/src/vm/NativeObject.cpp:2171)
0:38.92 GECKO(1158803) #20: bool NativeGetPropertyInline<(js::AllowGC)1>(JSContext*, js::MaybeRooted<js::NativeObject*, (js::AllowGC)1>::HandleType, js::MaybeRooted<JS::Value, (js::AllowGC)1>::HandleType, js::MaybeRooted<JS::PropertyKey, (js::AllowGC)1>::HandleType, IsNameLookup, js::MaybeRooted<JS::Value, (js::AllowGC)1>::MutableHandleType) (/home/leen/project-foxhound/js/src/vm/NativeObject.cpp:2319)
0:38.92 GECKO(1158803) #21: js::NativeGetProperty(JSContext*, JS::Handlejs::NativeObject*, JS::HandleJS::Value, JS::HandleJS::PropertyKey, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/NativeObject.cpp:2350)
0:38.92 GECKO(1158803) #22: js::GetProperty(JSContext*, JS::Handle<JSObject*>, JS::HandleJS::Value, JS::HandleJS::PropertyKey, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/ObjectOperations-inl.h:117)
0:38.92 GECKO(1158803) #23: js::GetProperty(JSContext*, JS::Handle<JSObject*>, JS::HandleJS::Value, js::PropertyName*, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/ObjectOperations-inl.h:124)
0:38.92 GECKO(1158803) #24: js::GetProperty(JSContext*, JS::HandleJS::Value, JS::Handlejs::PropertyName*, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:4804)
0:38.92 GECKO(1158803) #25: GetPropertyOperation(JSContext*, JS::Handlejs::PropertyName*, JS::HandleJS::Value, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:260)
0:38.92 GECKO(1158803) #26: js::Interpret(JSContext*, js::RunState&) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:3011)
0:38.92 GECKO(1158803) #27: MaybeEnterInterpreterTrampoline(JSContext*, js::RunState&) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:408)
0:38.92 GECKO(1158803) #28: js::RunScript(JSContext*, js::RunState&) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:466)
0:38.92 GECKO(1158803) #29: js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:624)
0:38.92 GECKO(1158803) #30: InternalCall(JSContext*, js::AnyInvokeArgs const&, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:659)
0:38.92 GECKO(1158803) #31: js::Call(JSContext*, JS::HandleJS::Value, JS::HandleJS::Value, js::AnyInvokeArgs const&, JS::MutableHandleJS::Value, js::CallReason) (/home/leen/project-foxhound/js/src/vm/Interpreter.cpp:691)
0:38.92 GECKO(1158803) #32: JS::Call(JSContext*, JS::HandleJS::Value, JS::HandleJS::Value, JS::HandleValueArray const&, JS::MutableHandleJS::Value) (/home/leen/project-foxhound/js/src/vm/CallAndConstruct.cpp:119)
0:38.93 GECKO(1158803) #33: mozilla::dom::EventHandlerNonNull::Call(mozilla::dom::BindingCallContext&, JS::HandleJS::Value, mozilla::dom::Event&, JS::MutableHandleJS::Value, mozilla::ErrorResult&) (EventHandlerBinding.cpp:65)
0:38.93 GECKO(1158803) #34: void mozilla::dom::EventHandlerNonNull::Call<nsCOMPtrmozilla::dom::EventTarget >(nsCOMPtrmozilla::dom::EventTarget const&, mozilla::dom::Event&, JS::MutableHandleJS::Value, mozilla::ErrorResult&, char const*, mozilla::dom::CallbackObject::ExceptionHandling, JS::Realm*) (/home/leen/project-foxhound/obj-tf-release/dist/include/mozilla/dom/EventHandlerBinding.h:82)
0:38.93 GECKO(1158803) #35: mozilla::JSEventHandler::HandleEvent(mozilla::dom::Event*) (/home/leen/project-foxhound/dom/events/JSEventHandler.cpp:201)
0:38.93 GECKO(1158803) #36: mozilla::EventListenerManager::HandleEventSingleListener(mozilla::EventListenerManager::Listener*, nsAtom*, mozilla::WidgetEvent*, mozilla::dom::Event*, mozilla::dom::EventTarget*, bool) (/home/leen/project-foxhound/dom/events/EventListenerManager.cpp:1347)
0:38.93 GECKO(1158803) #37: mozilla::EventListenerManager::HandleEventWithListenerArray(mozilla::EventListenerManager::ListenerArray*, nsAtom*, mozilla::EventMessage, nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event**, mozilla::dom::EventTarget*, bool) (/home/leen/project-foxhound/dom/events/EventListenerManager.cpp:1665)
0:38.93 GECKO(1158803) #38: mozilla::EventListenerManager::HandleEventInternal(nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event**, mozilla::dom::EventTarget*, nsEventStatus*, bool) (/home/leen/project-foxhound/dom/events/EventListenerManager.cpp:1562)
0:38.93 GECKO(1158803) #39: mozilla::EventListenerManager::HandleEvent(nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event**, mozilla::dom::EventTarget*, nsEventStatus*, bool) (/home/leen/project-foxhound/obj-tf-release/dist/include/mozilla/EventListenerManager.h:468)
0:38.93 GECKO(1158803) #40: mozilla::EventTargetChainItem::HandleEvent(mozilla::EventChainPostVisitor&, mozilla::ELMCreationDetector&) (/home/leen/project-foxhound/dom/events/EventDispatcher.cpp:368)
0:38.93 GECKO(1158803) #41: mozilla::EventTargetChainItem::HandleEventTargetChain(nsTArraymozilla::EventTargetChainItem&, mozilla::EventChainPostVisitor&, mozilla::EventDispatchingCallback*, mozilla::ELMCreationDetector&) (/home/leen/project-foxhound/dom/events/EventDispatcher.cpp:609)
0:38.93 GECKO(1158803) #42: mozilla::EventDispatcher::Dispatch(mozilla::dom::EventTarget*, nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event*, nsEventStatus*, mozilla::EventDispatchingCallback*, nsTArraymozilla::dom::EventTarget*) (/home/leen/project-foxhound/dom/events/EventDispatcher.cpp:1224)
0:38.93 GECKO(1158803) #43: mozilla::EventDispatcher::DispatchDOMEvent(mozilla::dom::EventTarget, mozilla::WidgetEvent*, mozilla::dom::Event*, nsPresContext*, nsEventStatus*) (/home/leen/project-foxhound/dom/events/EventDispatcher.cpp:1363)
0:38.93 GECKO(1158803) #44: nsWindowRoot::DispatchEvent(mozilla::dom::Event&, mozilla::dom::CallerType, mozilla::ErrorResult&) (/home/leen/project-foxhound/dom/base/nsWindowRoot.cpp:83)
0:38.93 GECKO(1158803) #45: mozilla::dom::EventTarget::DispatchEvent(mozilla::dom::Event&) (/home/leen/project-foxhound/dom/events/EventTarget.cpp:214)
0:38.93 GECKO(1158803) #46: mozilla::dom::MessageEventRunnable::DispatchDOMEvent(JSContext*, mozilla::dom::WorkerPrivate*, mozilla::DOMEventTargetHelper*, bool) (/home/leen/project-foxhound/dom/workers/MessageEventRunnable.cpp:81)
0:38.93 GECKO(1158803) #47: mozilla::dom::MessageEventRunnable::WorkerRun(JSContext*, mozilla::dom::WorkerPrivate*) (/home/leen/project-foxhound/dom/workers/MessageEventRunnable.cpp:95)
0:38.93 GECKO(1158803) #48: mozilla::dom::WorkerThreadRunnable::Run() (/home/leen/project-foxhound/dom/workers/WorkerRunnable.cpp:443)
0:38.93 GECKO(1158803) #49: nsThread::ProcessNextEvent(bool, bool*) (/home/leen/project-foxhound/xpcom/threads/nsThread.cpp:1199)
0:38.93 GECKO(1158803) #50: NS_ProcessNextEvent(nsIThread*, bool) (/home/leen/project-foxhound/xpcom/threads/nsThreadUtils.cpp:480)
0:38.93 GECKO(1158803) #51: mozilla::dom::WorkerPrivate::DoRunLoop(JSContext*) (/home/leen/project-foxhound/dom/workers/WorkerPrivate.cpp:3566)
0:38.93 GECKO(1158803) #52: mozilla::dom::workerinternals::(anonymous namespace)::WorkerThreadPrimaryRunnable::Run() (/home/leen/project-foxhound/dom/workers/RuntimeService.cpp:2159)
0:38.93 GECKO(1158803) #53: nsThread::ProcessNextEvent(bool, bool*) (/home/leen/project-foxhound/xpcom/threads/nsThread.cpp:1199)
0:38.93 GECKO(1158803) #54: NS_ProcessNextEvent(nsIThread*, bool) (/home/leen/project-foxhound/xpcom/threads/nsThreadUtils.cpp:480)
0:38.93 GECKO(1158803) #55: mozilla::ipc::MessagePumpForNonMainThreads::Run(base::MessagePump::Delegate*) (/home/leen/project-foxhound/ipc/glue/MessagePump.cpp:299)
0:38.93 GECKO(1158803) #56: MessageLoop::RunInternal() (/home/leen/project-foxhound/ipc/chromium/src/base/message_loop.cc:371)
0:38.93 GECKO(1158803) #57: MessageLoop::RunHandler() (/home/leen/project-foxhound/ipc/chromium/src/base/message_loop.cc:364)
0:38.93 GECKO(1158803) #58: MessageLoop::Run() (/home/leen/project-foxhound/ipc/chromium/src/base/message_loop.cc:345)
0:38.93 GECKO(1158803) #59: nsThread::ThreadFunc(void*) (/home/leen/project-foxhound/xpcom/threads/nsThread.cpp:372)
0:38.95 GECKO(1158803) #60: _pt_root (/home/leen/project-foxhound/nsprpub/pr/src/pthreads/ptthread.c:204)
0:38.95 GECKO(1158803) #61: ??? (/lib/x86_64-linux-gnu/libc.so.6 + 0x891f5)
0:38.95 GECKO(1158803) #62: ??? (/lib/x86_64-linux-gnu/libc.so.6 + 0x10989c)
0:38.95 GECKO(1158803) #63: ??? (???:???)
0:38.95 GECKO(1158803) [Socket 1158897, IPC I/O Child] WARNING: [300D5B1B6DEBD220.2D55D620A7C6CBA7]: Dropping message ''; no connection to unknown peer 1.1: file /home/leen/project-foxhound/ipc/glue/NodeController.cpp:364
0:38.95 GECKO(1158803) [Socket 1158897, Main Thread] WARNING: Shutting down Socket process early due to a crash!: file /home/leen/project-foxhound/netwerk/ipc/SocketProcessChild.cpp:234
0:38.95 Main app process: killed by SIGSEGV

[leeN]

We access the preferences from multiple threads, which causes assertions failures. I think this would require switching to static preferences, which might result in some general behavior changes.

Based on my reading, one of the blockers is that instead of a hash table with string lookups, we the codegen will generate a C++ function. This would require us to patch the codegen to include such a lookup table or somehow map from source/sink name to getter differently. One advantage is, that spidermonkey can apparently access these prefs. But that requires investigation about whether there is more than convention behind the restriction to javascript.option.*.

I can maybe give this a spin over the coming week to check whether migrating to static prefs is sensible.

[leeN]

We could accomplish this by replacing the sink names, which are char* constants, with an enum. This would allow for cheap lookups, e.g., by using EnumeratedArray and only convert towards the name upon adding it to the taint flow. This can map onto a std::function<bool()> reference to the static pref lookup method.