[Webkit-unassigned] [Bug 153995] New: Infinite loop when processing mouse events synchronously

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=153995

            Bug ID: 153995
           Summary: Infinite loop when processing mouse events
                    synchronously
    Classification: Unclassified
           Product: WebKit
           Version: WebKit Local Build
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebKit2
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: cgarcia at igalia.com
                CC: andersca at apple.com, darin at apple.com, sam at webkit.org
            Blocks: 153740

This happened with WTR in the GTK+ port after landing patch in bug #153740. The thing is that WTR forces events handling IPC messages to be synchronous. When a drag and drop operation is in progress, the web process ignores mouse move events and replies with DidReceiveEvent signal. The DidReceiveEvent message handler in WebPageProxy checks if we have a m_nextMouseMoveEvent and handles it, but when all this happens synchronously the m_nextMouseMoveEvent is the current one because we haven't returned yet from handleMouseEvent(). We need to invalidate the m_nextMouseMoveEvent before calling handleMouseEvent().

#0  0x00007ffff5bbb133 in IPC::Connection::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int, bool) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#1  0x00007ffff5bbc48c in IPC::Connection::sendSyncMessage(unsigned long, std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, std::chrono::duration<long, std::ratio<1l, 1000l> >, unsigned int) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#2  0x00007ffff5bbb1f5 in IPC::Connection::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int, bool) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#3  0x00007ffff5c20e37 in WebKit::ChildProcessProxy::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#4  0x00007ffff5c5c02a in bool WebKit::ChildProcessProxy::send<Messages::WebPage::MouseEvent>(Messages::WebPage::MouseEvent&&, unsigned long, unsigned int) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#5  0x00007ffff5c4579c in WebKit::WebPageProxy::handleMouseEvent(WebKit::NativeWebMouseEvent const&) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#6  0x00007ffff5c5170a in WebKit::WebPageProxy::didReceiveEvent(unsigned int, bool) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#7  0x00007ffff5e686f7 in WebKit::WebPageProxy::didReceiveMessage(IPC::Connection&, IPC::MessageDecoder&) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#8  0x00007ffff5bbf039 in IPC::MessageReceiverMap::dispatchMessage(IPC::Connection&, IPC::MessageDecoder&) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#9  0x00007ffff5c75102 in WebKit::WebProcessProxy::didReceiveMessage(IPC::Connection&, IPC::MessageDecoder&) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#10 0x00007ffff5bbb546 in IPC::Connection::dispatchMessage(std::unique_ptr<IPC::MessageDecoder, std::default_delete<IPC::MessageDecoder> >) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#11 0x00007ffff5bbb89e in IPC::Connection::SyncMessageState::dispatchMessages(IPC::Connection*) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#12 0x00007ffff5bbb4a1 in IPC::Connection::dispatchSyncMessage(IPC::MessageDecoder&) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#13 0x00007ffff5bbb5bd in IPC::Connection::dispatchMessage(std::unique_ptr<IPC::MessageDecoder, std::default_delete<IPC::MessageDecoder> >) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#14 0x00007ffff5bbb89e in IPC::Connection::SyncMessageState::dispatchMessages(IPC::Connection*) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#15 0x00007ffff5bbbd8f in IPC::Connection::waitForSyncReply(unsigned long, std::chrono::duration<long, std::ratio<1l, 1000l> >, unsigned int) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#16 0x00007ffff5bbc4b8 in IPC::Connection::sendSyncMessage(unsigned long, std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, std::chrono::duration<long, std::ratio<1l, 1000l> >, unsigned int) () from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#17 0x00007ffff5bbb1f5 in IPC::Connection::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int, bool) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
#18 0x00007ffff5c20e37 in WebKit::ChildProcessProxy::sendMessage(std::unique_ptr<IPC::MessageEncoder, std::default_delete<IPC::MessageEncoder> >, unsigned int) ()
   from /home/cgarcia/src/git/gnome/WebKit/WebKitBuild/Release/lib/libwebkit2gtk-4.0.so.37
......

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