Bug 172853

Summary: [GTK] Webkit sometimes hangs when going fullscreen in youtube videos
Product: WebKit Reporter: Cédric Bellegarde <cedric.bellegarde>
Component: MediaAssignee: Nobody <webkit-unassigned>
Status: REOPENED ---    
Severity: Major CC: bugs-noreply, cturner, magomez, mcatanzaro, pnormand
Priority: P1    
Version: Other   
Hardware: PC   
OS: Linux   

Description Cédric Bellegarde 2017-06-02 04:36:39 PDT 
When browsing Google+, if you play a youtube video, all is ok.
If you try to go fullscreen, webkit hangs.

GST_DEBUG doesn't show anything about hang, gstreamer is always playing the video.
Comment 1 Michael Catanzaro 2017-06-04 08:10:07 PDT 
I can't reproduce this.
Comment 2 Cédric Bellegarde 2017-06-19 06:11:11 PDT 
Can't reproduce anymore :-/
Comment 3 Michael Catanzaro 2017-06-23 18:27:39 PDT 
Ah, I thought we already had a bug report for this!

I still can't reproduce, but it now happens to me frequently enough on youtube.com that I'm confident this is still an issue. It's probably not a GStreamer issue, but certainly an issue with our GStreamer-based ports.
Comment 4 Miguel Gomez 2017-07-05 12:05:48 PDT 
In which version is this reproducible?
Comment 5 Michael Catanzaro 2017-07-05 17:43:37 PDT 
It definitely happens regularly in 2.16.3 and 2.16.5, but it's not reproducible on demand. Sometimes I can make it hang several times in a row, but sometimes it just doesn't want to hang.
Comment 6 Charlie Turner 2017-07-10 02:26:03 PDT 
Not sure how useful it will be yet, but perhaps a backtrace when it's hanging might be of use? I'm still unable to get a hang off of trunk or 2.16.3.
Comment 7 Michael Catanzaro 2017-07-10 05:27:02 PDT 
Yes, I'm regretting not getting one earlier when I could reproduce this. :/
Comment 8 Michael Catanzaro 2017-07-12 18:11:55 PDT 
OK, I hit this today and got a backtrace of the UI process when it was frozen. Unfortunately I don't see anything interesting:

Thread 21 (Thread 0x7f70d51cc700 (LWP 8796)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70e800b2f0, timeout=<optimized out>, context=0x7f70e8002030)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70e8002030, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70e80020f0) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f70d51cc700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 20 (Thread 0x7f71267fc700 (LWP 5916)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70cc0009c0, timeout=<optimized out>, context=0x7f70cc002e00)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70cc002e00, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70cc002fe0) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f71267fc700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 19 (Thread 0x7f70f23fd700 (LWP 26704)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70dc021b10, timeout=<optimized out>, context=0x7f70dc002d40)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70dc002d40, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70dc0037f0) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f70f23fd700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 18 (Thread 0x7f710a7ff700 (LWP 3214)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70d0000e00, timeout=<optimized out>, context=0x7f70d00008c0)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70d00008c0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70d00009b0) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f710a7ff700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 17 (Thread 0x7f70f33ff700 (LWP 3031)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70e4001370, timeout=<optimized out>, context=0x7f70e4000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70e4000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70e4001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f70f33ff700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 16 (Thread 0x7f70f3fff700 (LWP 3021)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70ec001370, timeout=<optimized out>, context=0x7f70ec000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70ec000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70ec001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f70f3fff700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 15 (Thread 0x7f7108ffc700 (LWP 3020)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70f8001370, timeout=<optimized out>, context=0x7f70f8000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70f8000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70f8001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f7108ffc700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 14 (Thread 0x7f71097fd700 (LWP 3019)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f70f4001370, timeout=<optimized out>, context=0x7f70f4000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f70f4000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f70f4001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f71097fd700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 13 (Thread 0x7f7109ffe700 (LWP 3008)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f7100001370, timeout=<optimized out>, context=0x7f7100000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f7100000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f7100001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f7109ffe700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 12 (Thread 0x7f710bfff700 (LWP 2999)):
#0  0x00007f7193900539 in syscall ()
    at ../sysdeps/unix/sysv/linux/x86_64/syscall.S:38
#1  0x00007f7193c555df in g_cond_wait (cond=cond@entry=0x55731e465ee8, mutex=mutex@entry=0x55731e465ee0) at gthread-posix.c:1395
#2  0x00007f7193be4b4b in g_async_queue_pop_intern_unlocked (queue=queue@entry=0x55731e465ee0, wait=wait@entry=1, end_time=end_time@entry=-1)
    at gasyncqueue.c:419
#3  0x00007f7193be4f77 in g_async_queue_pop (queue=0x55731e465ee0)
    at gasyncqueue.c:453
#4  0x00007f719d676c79 in run_history_service_thread (self=0x55731e467810 [EphyHistoryService]) at ephy-history-service.c:496
#5  0x00007f7193c37536 in g_thread_proxy (data=0x55731e2cf630) at gthread.c:784
#6  0x00007f7192e8036d in start_thread (arg=0x7f710bfff700)
    at pthread_create.c:456
#7  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 11 (Thread 0x7f7125ffb700 (LWP 2996)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f7110001370, timeout=<optimized out>, context=0x7f7110000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f7110000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f7110001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f7125ffb700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 10 (Thread 0x7f7126ffd700 (LWP 2994)):
#0  0x00007f7192e86dc6 in futex_abstimed_wait_cancelable (private=<optimized out>, abstime=0x7f7126ffc7e0, expected=0, futex_word=0x7f71871ce058)
    at ../sysdeps/unix/sysv/linux/futex-internal.h:205
#1  0x00007f7192e86dc6 in __pthread_cond_wait_common (abstime=0x7f7126ffc7e0, mutex=0x7f71871ce008, cond=0x7f71871ce030) at pthread_cond_wait.c:539
#2  0x00007f7192e86dc6 in __pthread_cond_timedwait (cond=0x7f71871ce030, mutex=0x7f71871ce008, abstime=0x7f7126ffc7e0) at pthread_cond_wait.c:667
#3  0x00007f7194c8d70a in WTF::ThreadCondition::timedWait(WTF::Mutex&, double) () at /lib64/libjavascriptcoregtk-4.0.so.18
#4  0x00007f7194c656d3 in WTF::ParkingLot::parkConditionallyImpl(void const*, WTF::ScopedLambda<bool ()> const&, WTF::ScopedLambda<void ()> const&, WTF::TimeWithDynamicClockType const&) () at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c5754a in WTF::sleep(double) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f71978f555d in std::_Function_handler<void (), WebKit::MemoryPressureMonitor::MemoryPressureMonitor()::{lambda()#1}>::_M_invoke(std::_Any_data const&) () at /lib64/libwebkit2gtk-4.0.so.37
#7  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#9  0x00007f7192e8036d in start_thread (arg=0x7f7126ffd700)
    at pthread_create.c:456
#10 0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 9 (Thread 0x7f71277fe700 (LWP 2991)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f7114001480, timeout=<optimized out>, context=0x7f7114000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f7114000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f7114001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f71277fe700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 8 (Thread 0x7f7127fff700 (LWP 2990)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f711c001480, timeout=<optimized out>, context=0x7f711c000900)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f711c000900, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f711c001240) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f7127fff700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 7 (Thread 0x7f712cd1d700 (LWP 2989)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f71200012e0, timeout=<optimized out>, context=0x7f7120000960)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f7120000960, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f71200012a0) at gmain.c:4168
#4  0x00007f7194c8f690 in WTF::RunLoop::run() ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7194c8e501 in std::_Function_handler<void (), WTF::WorkQueue::platformInitialize(char const*, WTF::WorkQueue::Type, WTF::WorkQueue::QOS)::{lambda()#1}>::_M_invoke(std::_Any_data const&) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7192e8036d in start_thread (arg=0x7f712cd1d700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 6 (Thread 0x7f712d51e700 (LWP 2988)):
#0  0x00007f7192e8681b in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7f71870fd058)
    at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  0x00007f7192e8681b in __pthread_cond_wait_common (abstime=0x0, mutex=0x7f71870fd008, cond=0x7f71870fd030) at pthread_cond_wait.c:502
#2  0x00007f7192e8681b in __pthread_cond_wait (cond=0x7f71870fd030, mutex=0x7f71870fd008) at pthread_cond_wait.c:655
#3  0x00007f7194c8d73b in WTF::ThreadCondition::timedWait(WTF::Mutex&, double) () at /lib64/libjavascriptcoregtk-4.0.so.18
#4  0x00007f7194c656d3 in WTF::ParkingLot::parkConditionallyImpl(void const*, WTF::ScopedLambda<bool ()> const&, WTF::ScopedLambda<void ()> const&, WTF::TimeWithDynamicClockType const&) () at /lib64/libjavascriptcoregtk-4.0.so.18
#5  0x00007f7198168a16 in WebCore::IconDatabase::syncThreadMainLoop() ()
    at /lib64/libwebkit2gtk-4.0.so.37
#6  0x00007f719816a498 in WebCore::IconDatabase::iconDatabaseSyncThread() ()
    at /lib64/libwebkit2gtk-4.0.so.37
#7  0x00007f7194c681e8 in WTF::threadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#8  0x00007f7194c8d11a in WTF::wtfThreadEntryPoint(void*) ()
    at /lib64/libjavascriptcoregtk-4.0.so.18
#9  0x00007f7192e8036d in start_thread (arg=0x7f712d51e700)
    at pthread_create.c:456
#10 0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 5 (Thread 0x7f717f32c700 (LWP 2987)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=10, fds=0x7f7174004270, timeout=<optimized out>, context=0x7f7178016180)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=0x7f7178016180, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3967
#3  0x00007f7193c10902 in g_main_loop_run (loop=0x7f7178018020) at gmain.c:4168
#4  0x00007f71951b6cb6 in gdbus_shared_thread_func (user_data=0x7f7178016150)
    at gdbusprivate.c:252
#5  0x00007f7193c37536 in g_thread_proxy (data=0x55731db6a720) at gthread.c:784
#6  0x00007f7192e8036d in start_thread (arg=0x7f717f32c700)
    at pthread_create.c:456
#7  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 4 (Thread 0x7f717fb2d700 (LWP 2986)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=2, fds=0x7f71700008c0, timeout=<optimized out>, context=0x7f7178004800)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=context@entry=0x7f7178004800, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at gmain.c:3967
#3  0x00007f7193c1067c in g_main_context_iteration (context=0x7f7178004800, may_block=may_block@entry=1) at gmain.c:4033
#4  0x00007f7193c106c1 in glib_worker_main (data=<optimized out>)
    at gmain.c:5824
#5  0x00007f7193c37536 in g_thread_proxy (data=0x55731db6a680) at gthread.c:784
#6  0x00007f7192e8036d in start_thread (arg=0x7f717fb2d700)
    at pthread_create.c:456
#7  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 3 (Thread 0x7f718032e700 (LWP 2985)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=1, fds=0x7f71780010e0, timeout=<optimized out>, context=0x55731db701e0)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=context@entry=0x55731db701e0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at gmain.c:3967
#3  0x00007f7193c1067c in g_main_context_iteration (context=context@entry=0x55731db701e0, may_block=may_block@entry=1) at gmain.c:4033
#4  0x00007f7180335f3d in dconf_gdbus_worker_thread (user_data=0x55731db701e0)
    at dconf-gdbus-thread.c:82
#5  0x00007f7193c37536 in g_thread_proxy (data=0x55731db6a0f0) at gthread.c:784
#6  0x00007f7192e8036d in start_thread (arg=0x7f718032e700)
    at pthread_create.c:456
#7  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 2 (Thread 0x7f7187b9e700 (LWP 2984)):
#0  0x00007f7192e8681b in futex_wait_cancelable (private=<optimized out>, expected=0, futex_word=0x7f7194e995e4 <bmalloc::PerProcess<bmalloc::Heap>::s_memory+3140>) at ../sysdeps/unix/sysv/linux/futex-internal.h:88
#1  0x00007f7192e8681b in __pthread_cond_wait_common (abstime=0x0, mutex=0x55731db53ae0, cond=0x7f7194e995b8 <bmalloc::PerProcess<bmalloc::Heap>::s_memory+3096>) at pthread_cond_wait.c:502
#2  0x00007f7192e8681b in __pthread_cond_wait (cond=0x7f7194e995b8 <bmalloc::PerProcess<bmalloc::Heap>::s_memory+3096>, mutex=0x55731db53ae0)
    at pthread_cond_wait.c:655
#3  0x00007f71929a2cec in __gthread_cond_wait (__mutex=<optimized out>, __cond=<optimized out>)
    at /usr/src/debug/gcc-7.1.1-20170622/obj-x86_64-redhat-linux/x86_64-redhat-linux/libstdc++-v3/include/x86_64-redhat-linux/bits/gthr-default.h:864
#4  0x00007f71929a2cec in std::condition_variable::wait(std::unique_lock<std::mutex>&) (this=<optimized out>, __lock=...)
    at ../../../../../libstdc++-v3/src/c++11/condition_variable.cc:53
#5  0x00007f7194c95517 in bmalloc::AsyncTask<bmalloc::Heap, void (bmalloc::Heap::*)()>::threadRunLoop() () at /lib64/libjavascriptcoregtk-4.0.so.18
#6  0x00007f7194c95659 in  () at /lib64/libjavascriptcoregtk-4.0.so.18
#7  0x00007f71929a902f in std::execute_native_thread_routine(void*) (__p=0x55731db53b40) at ../../../../../libstdc++-v3/src/c++11/thread.cc:83
#8  0x00007f7192e8036d in start_thread (arg=0x7f7187b9e700)
    at pthread_create.c:456
#9  0x00007f7193905b9f in clone ()
    at ../sysdeps/unix/sysv/linux/x86_64/clone.S:97

Thread 1 (Thread 0x7f719d9a1ac0 (LWP 2982)):
#0  0x00007f71938f9aad in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x00007f7193c10569 in g_main_context_poll (priority=<optimized out>, n_fds=5, fds=0x55731eb318e0, timeout=<optimized out>, context=0x55731db59ed0)
    at gmain.c:4271
#2  0x00007f7193c10569 in g_main_context_iterate (context=context@entry=0x55731db59ed0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at gmain.c:3967
#3  0x00007f7193c1067c in g_main_context_iteration (context=context@entry=0x55731db59ed0, may_block=may_block@entry=1) at gmain.c:4033
#4  0x00007f719518aebd in g_application_run (application=0x55731dbca220 [EphyShell], argc=<optimized out>, argv=<optimized out>) at gapplication.c:2381
#5  0x000055731d1c6885 in main (argc=<optimized out>, argv=<optimized out>)
    at ephy-main.c:432

Unfortunately I had a ton of web processes open, and with the UI process frozen it was not possible to determine which web process corresponded to my YouTube tab, so no backtrace for the web process yet.