[webkit-help] JSCore and multi-threading : WTF/ThreadRestrictionVerifier single-threaded mode default behaviour

Sun Nov 18 14:31:54 PST 2012

JavaScriptCore can support multi-threaded operation with some restrictions. You can use separate virtual machines (with their own heap etc) on separate threads. Or if you want to use one VM on multiple threads, you must lock to guarantee mutual exclusion. It sounds to me like the assert in DateInstanceData may be a bug, but I am not sure. I suggest filing a bug report, assuming the issue still exists on trunk (WebKit developers do not usually pay much attention to bugs reported against branches off the trunk, since those are either experimental or vendor-owned).

Regards,
Maciej

On Nov 16, 2012, at 2:41 AM, Guy Hermann <guy.hermann at 4d.com> wrote:

> 
> Hi all,
> 
> all that follows is related to WebKit branch 536.26.
> 
> We are currently using JSCore/WTF in a multi-threaded environment and are facing an ASSERT (see backtrace below) mainly due to the fact that DateInstanceData inherits from RefCounted which contains a ThreadRestrictionVerifier (which isSafeToUse method returns false in our case).
> 
> This ThreadRestrictionVerifier has only one constructor and that constructor sets (by default) its internal mode to SingleThreadVerificationMode: in other words, all the JSCore RefCounted (by inheritance) instances are assumed to work in a single-threaded environment; so JSCore as a whole is by default customized to work in a single-threaded environment.
> 
> Q1: Is JSCore able to work in a multi-threaded environment (with an unchanged codebase)?
> 
> Q2.1: if Q1 is yes, is there is a way to set all the RefCounted instances created by JSCore multi-thread compatible with only a slight modification of JSCore codebase. Indeed and as far as I can see, one would need to change the mode of all the  instanciated ThreadVerifiers to MutexVerificationMode.
> 
> Q2.2: if Q1 is yes, can NoVerificationMode be used in a multi-threaded environment (I don't think so)
> 
> thanks for your help
> 
>  
>  JavaScriptCore_Debug.dll!WTF::RefCountedBase::derefBase() Line 129 + 0x38 bytes C++
> JavaScriptCore_Debug.dll!WTF::RefCounted<JSC::DateInstanceData>::deref() Line 189 + 0x8 bytes C++
> JavaScriptCore_Debug.dll!WTF::derefIfNotNull<JSC::DateInstanceData>(JSC::DateInstanceData * ptr=0xffe28f30) Line 53 C++
> JavaScriptCore_Debug.dll!WTF::RefPtr<JSC::DateInstanceData>::~RefPtr<JSC::DateInstanceData>() Line 56 + 0x19 bytes C++
> JavaScriptCore_Debug.dll!JSC::DateInstance::~DateInstance() + 0x46 bytes C++
> > JavaScriptCore_Debug.dll!JSC::DateInstance::destroy(JSC::JSCell * cell=0x11f7d380) Line 59 C++
> JavaScriptCore_Debug.dll!JSC::MarkedBlock::callDestructor(JSC::JSCell * cell=0x11f7d380) Line 74 + 0x12 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedBlock::specializedSweep<3,1,1>() Line 101 C++
> JavaScriptCore_Debug.dll!JSC::MarkedBlock::sweepHelper<1>(JSC::MarkedBlock::SweepMode sweepMode=SweepToFreeList) Line 142 + 0x12 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedBlock::sweep(JSC::MarkedBlock::SweepMode sweepMode=SweepToFreeList) Line 121 + 0x10 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedAllocator::tryAllocateHelper() Line 33 + 0x10 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedAllocator::tryAllocate() Line 52 + 0x8 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedAllocator::allocateSlowCase() Line 68 + 0x8 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedAllocator::allocate() Line 77 + 0x8 bytes C++
> JavaScriptCore_Debug.dll!JSC::MarkedSpace::allocateWithDestructor(unsigned int bytes=0x00000040) Line 160 C++
> JavaScriptCore_Debug.dll!JSC::Heap::allocateWithDestructor(unsigned int bytes=0x00000040) Line 355 C++
> JavaScriptCore_Debug.dll!JSC::allocateCell<JSC::JSFinalObject>(JSC::Heap & heap={...}) Line 336 + 0xa bytes C++
> JavaScriptCore_Debug.dll!JSC::JSFinalObject::create(JSC::ExecState * exec=0x144e0318, JSC::Structure * structure=0x11eef420) Line 395 + 0xe bytes C++
> JavaScriptCore_Debug.dll!JSC::constructEmptyObject(JSC::ExecState * exec=0x144e0318, JSC::Structure * structure=0x11eef420) Line 466 + 0xd bytes C++
> JavaScriptCore_Debug.dll!JSC::constructEmptyObject(JSC::ExecState * exec=0x144e0318, JSC::JSGlobalObject * globalObject=0x11f0fc40) Line 431 + 0x12 bytes C++
> JavaScriptCore_Debug.dll!JSC::constructEmptyObject(JSC::ExecState * exec=0x144e0318) Line 436 + 0x12 bytes C++
> JavaScriptCore_Debug.dll!cti_op_new_object(void * * args=0x11a9f580) Line 1382 + 0xc bytes C++
> JavaScriptCore_Debug.dll!@cti_op_create_this at 4() + 0x20f bytes C++
> JavaScriptCore_Debug.dll!JSC::JITCode::execute(JSC::RegisterFile * registerFile=0xffda2bdc, JSC::ExecState * callFrame=0x144e0048, JSC::JSGlobalData * globalData=0xffd9b400) Line 127 + 0x2d bytes C++
> JavaScriptCore_Debug.dll!JSC::Interpreter::executeCall(JSC::ExecState * callFrame=0x11f0fcb8, JSC::JSObject * function=0x11f7d600, JSC::CallType callType=CallTypeJS, const JSC::CallData & callData={...}, JSC::JSValue thisValue={...}, const JSC::ArgList & args={...}) Line 1342 + 0x2a bytes C++
> JavaScriptCore_Debug.dll!JSC::call(JSC::ExecState * exec=0x11f0fcb8, JSC::JSValue functionObject={...}, JSC::CallType callType=CallTypeJS, const JSC::CallData & callData={...}, JSC::JSValue thisValue={...}, const JSC::ArgList & args={...}) Line 67 + 0x3c bytes C++
> JavaScriptCore_Debug.dll!JSObjectCallAsFunction(const OpaqueJSContext * ctx=0x11f0fcb8, OpaqueJSValue * object=0x11f7d600, OpaqueJSValue * thisObject=0x11f0fc40, unsigned int argumentCount=0x00000002, const OpaqueJSValue * const * arguments=0x0f615ce8, const OpaqueJSValue * * exception=0x11a9f904) Line 497 + 0x5c bytes C++
> 4DJavaScriptDebug.dll!xbox::VJSObject::CallFunction(const xbox::VJSObject & inFunctionObject={...}, const std::vector<xbox::VJSValue,std::allocator<xbox::VJSValue> > * inValues=[0x00000002]({fContext=0x11f0fcb8 fValue=0x11f71c40 },{fContext=0x11f0fcb8 fValue=0x11f71c00 }), xbox::VJSValue * outResult=0x11a9facc, const OpaqueJSValue * * outException=0x11a9f9cc, const xbox::VFilePath * inFullPath=0x00000000) Line 470 + 0x30 bytes C++
> 4DJavaScriptDebug.dll!xbox::VJSObject::CallMemberFunction(const xbox::VString & inFunctionName={...}, const std::vector<xbox::VJSValue,std::allocator<xbox::VJSValue> > * inValues=[0x00000002]({fContext=0x11f0fcb8 fValue=0x11f71c40 },{fContext=0x11f0fcb8 fValue=0x11f71c00 }), xbox::VJSValue * outResult=0x11a9facc, const OpaqueJSValue * * outException=0x11a9f9cc, const xbox::VFilePath * inFullPath=0x00000000) Line 203 + 0x40 bytes C++
> Wakanda Server.exe!VRIAJSCallbackGlobalFunction::Call(xbox::VJSContext & inContext={...}, const std::vector<xbox::VJSValue,std::allocator<xbox::VJSValue> > * inParameters=[0x00000002]({fContext=0x11f0fcb8 fValue=0x11f71c40 },{fContext=0x11f0fcb8 fValue=0x11f71c00 }), xbox::VJSValue * outResult=0x11a9facc) Line 1236 + 0x1e bytes C++
> Wakanda Server.exe!VJSRequestHandler::HandleRequest(IHTTPResponse * inResponse=0x0f4ac724) Line 116 + 0x28 bytes C++
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> Guy Hermann
> Développeur Senior
> Email :	guy.hermann at 4d.com
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