Created attachment 300825 [details] Full backtrace This is probably a follow-up bug to bug #167003: * Load http://www.riverfronttimes.com/newsblog/2017/02/07/unions-seek-to-block-missouri-right-to-work-referendum-vote-likely-this-fall * Scroll down * Crash Full backtrace attached. Truncated: Thread 1 (Thread 0x7fb124c12ac0 (LWP 20285)): #0 0x00007fb1164565ec in WTFCrash () at ../../Source/WTF/wtf/Assertions.cpp:323 No locals. #1 0x00007fb11ff37828 in WTF::WeakReference<WebCore::MainThreadNotifier<MainThreadSourceNotification> >::clear (this=0x7fb0aa3d4210) at ../../Source/WTF/wtf/WeakPtr.h:65 __PRETTY_FUNCTION__ = "void WTF::WeakReference<T>::clear() [with T = WebCore::MainThreadNotifier<MainThreadSourceNotification>]" #2 0x00007fb11ff369c8 in WTF::WeakPtrFactory<WebCore::MainThreadNotifier<MainThreadSourceNotification> >::~WeakPtrFactory (this=0xd0a00c8, __in_chrg=<optimized out>) at ../../Source/WTF/wtf/WeakPtr.h:122 No locals. #3 0x00007fb11ff3653a in (anonymous namespace)::MainThreadNotifier<MainThreadSourceNotification>::~MainThreadNotifier (this=0xd0a00c8, __in_chrg=<optimized out>) at ../../Source/WebCore/platform/graphics/gstreamer/MainThreadNotifier.h:30 No locals. #4 0x00007fb11ff365f2 in _WebKitWebSrcPrivate::~_WebKitWebSrcPrivate ( this=0xd0a0040, __in_chrg=<optimized out>) at ../../Source/WebCore/platform/graphics/gstreamer/WebKitWebSourceGStreamer.cpp:132 No locals. #5 0x00007fb11ff2cc16 in webKitWebSrcFinalize (object=0xd0a0100) at ../../Source/WebCore/platform/graphics/gstreamer/WebKitWebSourceGStreamer.cpp:331 src = 0xd0a0100 priv = 0xd0a0040 Looks like another thread-safety bug in the _WebKitWebSrcPrivate destructor. Note: bug #152043 looks related.