So I don't really have STR, I was just using Firefox Nightly (latest ones) and it froze at some point. I attached a gdb to it to see what was going on, and saw the following stack traces, which indicate a deadlock: Firefox: #0 __lll_lock_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135 #1 0x00007f628af1768d in _L_lock_1082 () from /lib/x86_64-linux-gnu/libpthread.so.0 #2 0x00007f628af17607 in __GI___pthread_mutex_lock (mutex=0x7f625d561ec0) at ../nptl/pthread_mutex_lock.c:134 #3 0x00007f62897e9181 in PR_Lock () from /home/ben/.files/private/bin/firefox/libnspr4.so #4 0x00007f627d7a96bb in mozilla::layers::APZCTreeManager::GetScreenToApzcTransform(mozilla::layers::AsyncPanZoomController const*) const () from /home/ben/.files/private/bin/firefox/libxul.so #5 0x00007f627d7ad0ac in mozilla::layers::TransformDisplacement(mozilla::layers::APZCTreeManager*, mozilla::layers::AsyncPanZoomController*, mozilla::layers::AsyncPanZoomController*, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&) () from /home/ben/.files/private/bin/firefox/libxul.so #6 0x00007f627d7b437f in mozilla::layers::APZCTreeManager::DispatchScroll(mozilla::layers::AsyncPanZoomController*, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::layers::OverscrollHandoffState&) () from /home/ben/.files/private/bin/firefox/libxul.so #7 0x00007f627d7b4285 in mozilla::layers::AsyncPanZoomController::AttemptScroll(mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::gfx::Poin---Type <return> to continue, or q <return> to quit--- tTyped<mozilla::ParentLayerPixel, float>&, mozilla::layers::OverscrollHandoffState&) () from /home/ben/.files/private/bin/firefox/libxul.so #8 0x00007f627d7b4346 in mozilla::layers::APZCTreeManager::DispatchScroll(mozilla::layers::AsyncPanZoomController*, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::gfx::PointTyped<mozilla::ParentLayerPixel, float>&, mozilla::layers::OverscrollHandoffState&) () from /home/ben/.files/private/bin/firefox/libxul.so #9 0x00007f627d7b488c in mozilla::layers::AsyncPanZoomController::OnScrollWheel(mozilla::ScrollWheelInput const&) () from /home/ben/.files/private/bin/firefox/libxul.so #10 0x00007f627d7bda0b in mozilla::layers::AsyncPanZoomController::HandleInputEvent(mozilla::InputData const&, mozilla::gfx::Matrix4x4 const&) () from /home/ben/.files/private/bin/firefox/libxul.so #11 0x00007f627d7bd41b in mozilla::layers::InputQueue::MaybeHandleCurrentBlock(mozilla::layers::CancelableBlockState*, mozilla::InputData const&) () from /home/ben/.files/private/bin/firefox/libxul.so #12 0x00007f627d7be098 in mozilla::layers::InputQueue::ReceiveScrollWheelInput(nsRefPtr<mozilla::layers::AsyncPanZoomController> const&, bool, mozilla::ScrollWheelInput const&, unsigned long*) () from /home/ben/.files/private/bin/firefox/libxul.so #13 0x00007f627d7be119 in mozilla::layers::InputQueue::ReceiveInputEvent(nsRefPtr<mozilla::layers::AsyncPanZoomController> const&, bool, mozilla::InputData const&, unsigned long*) () from /home/ben/.files/private/bin/firefox/libxul.so ---Type <return> to continue, or q <return> to quit--- #14 0x00007f627d7be53f in mozilla::layers::APZCTreeManager::ReceiveInputEvent(mozilla::InputData&, mozilla::layers::ScrollableLayerGuid*, unsigned long*) () from /home/ben/.files/private/bin/firefox/libxul.so #15 0x00007f627d7bea9c in mozilla::layers::APZCTreeManager::ProcessWheelEvent(mozilla::WidgetWheelEvent&, mozilla::layers::ScrollableLayerGuid*, unsigned long*) () from /home/ben/.files/private/bin/firefox/libxul.so #16 0x00007f627d7c01d0 in mozilla::layers::APZCTreeManager::ReceiveInputEvent(mozilla::WidgetInputEvent&, mozilla::layers::ScrollableLayerGuid*, unsigned long*) () from /home/ben/.files/private/bin/firefox/libxul.so #17 0x00007f627e3faf35 in nsBaseWidget::DispatchAPZAwareEvent(mozilla::WidgetInputEvent*) () from /home/ben/.files/private/bin/firefox/libxul.so #18 0x00007f627e426f64 in nsWindow::OnScrollEvent(_GdkEventScroll*) () from /home/ben/.files/private/bin/firefox/libxul.so #19 0x00007f627e426f9e in scroll_event_cb(_GtkWidget*, _GdkEventScroll*) () from /home/ben/.files/private/bin/firefox/libxul.so #20 0x00007f6287d8cd6e in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0 #21 0x00007f62856145e7 in ?? () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 #22 0x00007f628562d088 in g_signal_emit_valist () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 #23 0x00007f628562dce2 in g_signal_emit () from /usr/lib/x86_64-linux-gnu/libgobject-2.0.so.0 #24 0x00007f6287eb5c64 in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0 ---Type <return> to continue, or q <return> to quit--- #25 0x00007f6287d8b0bc in ?? () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0 #26 0x00007f6287d8c94a in gtk_main_do_event () from /usr/lib/x86_64-linux-gnu/libgtk-3.so.0 #27 0x00007f6287990c32 in ?? () from /usr/lib/x86_64-linux-gnu/libgdk-3.so.0 #28 0x00007f6285344e04 in g_main_context_dispatch () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 #29 0x00007f6285345048 in ?? () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 #30 0x00007f62853450ec in g_main_context_iteration () from /lib/x86_64-linux-gnu/libglib-2.0.so.0 #31 0x00007f627ceec11f in nsAppShell::ProcessNextNativeEvent(bool) () from /home/ben/.files/private/bin/firefox/libxul.so #32 0x00007f627ceeb224 in nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal*, bool) () from /home/ben/.files/private/bin/firefox/libxul.so #33 0x00007f627ce2d838 in nsThread::ProcessNextEvent(bool, bool*) () from /home/ben/.files/private/bin/firefox/libxul.so #34 0x00007f627ce3679e in NS_ProcessNextEvent(nsIThread*, bool) () from /home/ben/.files/private/bin/firefox/libxul.so #35 0x00007f627ce4e833 in mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) () from /home/ben/.files/private/bin/firefox/libxul.so #36 0x00007f627d3b8a13 in MessageLoop::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #37 0x00007f627e40c168 in nsBaseAppShell::Run() () from /home/ben/.files/private/bin/firefox/libxul.so ---Type <return> to continue, or q <return> to quit--- #38 0x00007f627e9cafec in nsAppStartup::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #39 0x00007f627ea019d9 in XREMain::XRE_mainRun() () from /home/ben/.files/private/bin/firefox/libxul.so #40 0x00007f627ea04028 in XREMain::XRE_main(int, char**, nsXREAppData const*) () from /home/ben/.files/private/bin/firefox/libxul.so #41 0x00007f627ea042b8 in XRE_main () from /home/ben/.files/private/bin/firefox/libxul.so #42 0x0000000000413836 in do_main(int, char**, nsIFile*) () #43 0x000000000040597e in main () plugin-container: #0 pthread_cond_wait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185 #1 0x00007f2909d40519 in PR_WaitCondVar () from /home/ben/.files/private/bin/firefox/libnspr4.so #2 0x00007f2905833735 in mozilla::CondVar::Wait(unsigned int) [clone .isra.7] () from /home/ben/.files/private/bin/firefox/libxul.so #3 0x00007f2905dd6aca in mozilla::ipc::MessageChannel::WaitForSyncNotify() () from /home/ben/.files/private/bin/firefox/libxul.so #4 0x00007f2905ddddc4 in mozilla::ipc::MessageChannel::Send(IPC::Message*, IPC::Message*) () from /home/ben/.files/private/bin/firefox/libxul.so #5 0x00007f2905e5eee0 in mozilla::layers::PLayerTransactionChild::SendUpdate(nsTArray<mozilla::layers::Edit> const&, unsigned long const&, mozilla::layers::TargetConfig const&, nsTArray<mozilla::layers::PluginWindowData> const&, bool const&, bool const&, unsigned int const&, bool const&, mozilla::TimeStamp const&, int const&, nsTArray<mozilla::layers::EditReply>*) () from /home/ben/.files/private/bin/firefox/libxul.so #6 0x00007f2906208eae in mozilla::layers::ShadowLayerForwarder::EndTransaction(nsTArray<mozilla::layers::EditReply>*, nsIntRegion const&, unsigned long, bool, unsigned int, bool, mozilla::TimeStamp const&, bool*) () from /home/ben/.files/private/bin/firefox/libxul.so #7 0x00007f29061e45e6 in mozilla::layers::ClientLayerManager::ForwardTransaction(bool) () from /home/ben/.files/private/bin/firefox/libxul.so #8 0x00007f29061e4841 in mozilla::layers::ClientLayerManager::EndTransaction(void (*)(mozilla::layers::PaintedLayer*, gfxContext*, nsIntRegion const&, nsIntRegion const&, mozilla::layers::DrawRegionClip, nsIntRegion const&, void*), void*, mozilla::layers::LayerManager::EndTransactionFlags) () from /home/ben/.files/private/bin/firefox/libxul.so #9 0x00007f2906f82156 in nsDisplayList::PaintRoot(nsDisplayListBuilder*, nsRenderingContext*, unsigned int) () from /home/ben/.files/private/bin/firefox/libxul.so #10 0x00007f2906fbba73 in nsLayoutUtils::PaintFrame(nsRenderingContext*, nsIFrame*, nsRegion const&, unsigned int, unsigned int) () from /home/ben/.files/private/bin/firefox/libxul.so #11 0x00007f2906fbc4c6 in PresShell::Paint(nsView*, nsRegion const&, unsigned int) () from /home/ben/.files/private/bin/firefox/libxul.so #12 0x00007f2906dffe91 in nsViewManager::ProcessPendingUpdatesPaint(nsIWidget*) () from /home/ben/.files/private/bin/firefox/libxul.so #13 0x00007f2906e000dc in nsViewManager::ProcessPendingUpdatesForView(nsView*, bool) () from /home/ben/.files/private/bin/firefox/libxul.so #14 0x00007f290592f24e in nsRefreshDriver::Tick(long, mozilla::TimeStamp) () from /home/ben/.files/private/bin/firefox/libxul.so #15 0x00007f2906f4a413 in mozilla::RefreshDriverTimer::Tick(long, mozilla::TimeStamp) () from /home/ben/.files/private/bin/firefox/libxul.so #16 0x00007f2906f4a52e in mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::TickRefreshDriver(mozilla::TimeStamp) () from /home/ben/.files/private/bin/firefox/libxul.so #17 0x00007f2906f4a66a in mozilla::VsyncRefreshDriverTimer::RefreshDriverVsyncObserver::NotifyVsync(mozilla::TimeStamp) () from /home/ben/.files/private/bin/firefox/libxul.so #18 0x00007f29070cbe7f in mozilla::layout::VsyncChild::RecvNotify(mozilla::TimeStamp const&) () from /home/ben/.files/private/bin/firefox/libxul.so #19 0x00007f2905ee286f in mozilla::layout::PVsyncChild::OnMessageReceived(IPC::Message const&) () from /home/ben/.files/private/bin/firefox/libxul.so #20 0x00007f2905e042e3 in mozilla::ipc::PBackgroundChild::OnMessageReceived(IPC::Message const&) () from /home/ben/.files/private/bin/firefox/libxul.so #21 0x00007f2905855691 in mozilla::ipc::MessageChannel::DispatchAsyncMessage(IPC::Message const&) () from /home/ben/.files/private/bin/firefox/libxul.so #22 0x00007f290585613c in mozilla::ipc::MessageChannel::DispatchMessage(IPC::Message const&) () from /home/ben/.files/private/bin/firefox/libxul.so #23 0x00007f2905856ce5 in mozilla::ipc::MessageChannel::OnMaybeDequeueOne() () from /home/ben/.files/private/bin/firefox/libxul.so #24 0x00007f2905853fae in MessageLoop::DoWork() () from /home/ben/.files/private/bin/firefox/libxul.so #25 0x00007f2905dd5680 in mozilla::ipc::DoWorkRunnable::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #26 0x00007f2905834b82 in nsThread::ProcessNextEvent(bool, bool*) () from /home/ben/.files/private/bin/firefox/libxul.so #27 0x00007f290583d79e in NS_ProcessNextEvent(nsIThread*, bool) () from /home/ben/.files/private/bin/firefox/libxul.so #28 0x00007f29058558af in mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) () from /home/ben/.files/private/bin/firefox/libxul.so #29 0x00007f2905dbfa13 in MessageLoop::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #30 0x00007f2906e13168 in nsBaseAppShell::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #31 0x00007f290740b7a2 in XRE_RunAppShell () from /home/ben/.files/private/bin/firefox/libxul.so #32 0x00007f2905dbfa13 in MessageLoop::Run() () from /home/ben/.files/private/bin/firefox/libxul.so #33 0x00007f290740be77 in XRE_InitChildProcess () from /home/ben/.files/private/bin/firefox/libxul.so #34 0x0000000000416be1 in content_process_main(int, char**) () #35 0x00007f2903eb0ec5 in __libc_start_main (main=0x408c20 <main>, argc=10, argv=0x7fff233dc738, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff233dc728) at libc-start.c:287 #36 0x0000000000416445 in _start () Here's some info about my graphics setup from about:support that might be relevant (also, I'm using e10s): Graphics Adapter Description NVIDIA Corporation -- GeForce GT 750M/PCIe/SSE2 Asynchronous Pan/Zoom wheel input enabled Device ID GeForce GT 750M/PCIe/SSE2 Driver Version 4.5.0 NVIDIA 346.96 GPU Accelerated Windows 0/1 Basic (OMTC) Supports Hardware H264 Decoding No; Vendor ID NVIDIA Corporation WebGL Renderer NVIDIA Corporation -- GeForce GT 750M/PCIe/SSE2 windowLayerManagerRemote true AzureCanvasBackend cairo AzureContentBackend cairo AzureFallbackCanvasBackend none AzureSkiaAccelerated 0 CairoUseXRender 1 (#0) Error Invalid draw target type specified: 0 (#3) Error Failed GetAsDrawTarget true, 0x7f2c431cd000 + 16, Size(160,90), 640, 1 (#4) Error Invalid draw target type specified: 0 (#5) Error Failed GetAsDrawTarget true, 0x7f2c42e25000 + 16, Size(160,90), 640, 1 (#6) Error Invalid draw target type specified: 0 (#7) Error Failed GetAsDrawTarget true, 0x7f2c436ee000 + 16, Size(160,90), 640, 1

If you hit this again, can you also print a stack trace from the Compositor thread in the parent process? That's the thread that the content process main thread is blocking on here.

Happened again today, see attached debug log (contains main process main thread bt, plus compositor thread on the main process, and plugin-container).

Perfect, thanks!

This is a deadlock caused by a violation of APZ lock ordering [1]: OnScrollWheel() is calling CallDispatchScroll(), which might need to acquire the tree lock, while holding the APZC lock. Looks like a regression from bug 1152011. [1] https://dxr.mozilla.org/mozilla-central/rev/607a236c229994df99766c005f9ec729532d7747/gfx/layers/apz/src/APZCTreeManager.h#57

Bug 1211506 - Respect the APZ lock ordering in AsyncPanZoomController::OnScrollWheel(). r=mstange

Comment on attachment 8675122 [details] MozReview Request: Bug 1211506 - Respect the APZ lock ordering in AsyncPanZoomController::OnScrollWheel(). r=mstange https://reviewboard.mozilla.org/r/22331/#review19947

Adjusted comment and landed.