Using a debug device build of WebKit for iOS r186893, the assertion ASSERT(m_suspendMessageCount >= 0) fails ProcessThrottler::didCancelProcessSuspension() when switching tabs with the following backtrace: Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: ASSERTION FAILED: m_suspendMessageCount >= 0 Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: /Volumes/Data/WebKitDevGit/OpenSource/Source/WebKit2/UIProcess/ProcessThrottler.cpp(114) : void WebKit::ProcessThrottler::didCancelProcessSuspension() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 1 0x100c25c20 WTFCrash Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 2 0x109e4d928 WebKit::ProcessThrottler::didCancelProcessSuspension() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 3 0x109dd501c WebKit::NetworkProcessProxy::didCancelProcessSuspension() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 4 0x109ddb440 void IPC::callMemberFunctionImpl<WebKit::NetworkProcessProxy, void (WebKit::NetworkProcessProxy::*)(), std::__1::tuple<> >(WebKit::NetworkProcessProxy*, void (WebKit::NetworkProcessProxy::*)(), std::__1::tuple<>&&, std::index_sequence<>) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 5 0x109ddb3b4 void IPC::callMemberFunction<WebKit::NetworkProcessProxy, void (WebKit::NetworkProcessProxy::*)(), std::__1::tuple<>, std::make_index_sequence<0ul> >(std::__1::tuple<>&&, WebKit::NetworkProcessProxy*, void (WebKit::NetworkProcessProxy::*)()) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 6 0x109dda5e0 void IPC::handleMessage<Messages::NetworkProcessProxy::DidCancelProcessSuspension, WebKit::NetworkProcessProxy, void (WebKit::NetworkProcessProxy::*)()>(IPC::MessageDecoder&, WebKit::NetworkProcessProxy*, void (WebKit::NetworkProcessProxy::*)()) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 7 0x109dd9cc0 WebKit::NetworkProcessProxy::didReceiveNetworkProcessProxyMessage(IPC::Connection&, IPC::MessageDecoder&) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 8 0x109dd43e0 WebKit::NetworkProcessProxy::didReceiveMessage(IPC::Connection&, IPC::MessageDecoder&) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 9 0x109dd4418 non-virtual thunk to WebKit::NetworkProcessProxy::didReceiveMessage(IPC::Connection&, IPC::MessageDecoder&) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 10 0x109bfe194 IPC::Connection::dispatchMessage(IPC::MessageDecoder&) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 11 0x109bf83fc IPC::Connection::dispatchMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 12 0x109bfe554 IPC::Connection::dispatchOneMessage() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 13 0x109c08c98 IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >)::$_10::operator()() const Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 14 0x109c08c70 void std::__1::__invoke_void_return_wrapper<void>::__call<IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >)::$_10&>(IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >)::$_10&&&) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 15 0x109c08a4c std::__1::__function::__func<IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >)::$_10, std::__1::allocator<IPC::Connection::enqueueIncomingMessage(std::__1::unique_ptr<IPC::MessageDecoder, std::__1::default_delete<IPC::MessageDecoder> >)::$_10>, void ()>::operator()() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 16 0x10076dd9c std::__1::function<void ()>::operator()() const Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 17 0x100c585d4 WTF::RunLoop::performWork() Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 18 0x100c597ec WTF::RunLoop::performWork(void*) Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 19 0x182ecfd6c <redacted> Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 20 0x182ecf800 <redacted> Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 21 0x182ecd500 <redacted> Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 22 0x182dfd280 CFRunLoopRunSpecific Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 23 0x18e5000cc GSEventRunModal Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 24 0x18862ee4c UIApplicationMain Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 25 0x1000073b4 Jul 18 13:29:44 iPhone MobileSafari[1517] <Notice>: 26 0x198e6a8b8 <redacted>
Created attachment 257124 [details] Patch
<rdar://problem/21906759>
Comment on attachment 257124 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=257124&action=review r=me > Source/WebKit2/NetworkProcess/NetworkProcess.cpp:525 > + // we do not because we have nothing to cancel. NetworkProcessProxy::DidCancelProcessSuspension should nit: I think saying that we are not cancellable because prepareToSuspend() sends back the ProcessReadyToSuspend IPC message synchronously would be clearer.
(In reply to comment #3) > > Source/WebKit2/NetworkProcess/NetworkProcess.cpp:525 > > + // we do not because we have nothing to cancel. NetworkProcessProxy::DidCancelProcessSuspension should > > nit: I think saying that we are not cancellable because prepareToSuspend() > sends back the ProcessReadyToSuspend IPC message synchronously would be > clearer. Notice that the IPC message ProcessReadyToSuspend is sent asynchronously. I understand what you are trying to convey by using the word "synchronously" - the network process already replied to the NetworkProcess::PrepareToSuspend message with a NetworkProcessProxy::ProcessReadyToSuspend message and hence should not reply again with a NetworkProcessProxy::DidCancelProcessSuspension. I will update the comment in this function to read to help clarify : Although it is tempting to send a NetworkProcessProxy::DidCancelProcessSuspension message from here we do not because prepareToSuspend() already replied with a NetworkProcessProxy::ProcessReadyToSuspend message. NetworkProcessProxy::DidCancelProcessSuspension should only be sent if and only if we have not replied to a NetworkProcess::PrepareToSuspend message with a NetworkProcessProxy::ProcessReadyToSuspend message.
(In reply to comment #4) > I will update the comment in this function to read to help clarify : I meant to write: I will update the comment in this function to help clarify why we do not send a NetworkProcessProxy::DidCancelProcessSuspension message.
Committed r187124: <http://trac.webkit.org/changeset/187124>