wayland crash debugging help required

[Pekka Paalanen]

On Wed, 30 Mar 2016 12:01:58 +0530
Vikas Patil <vikasmpatil at gmail.com> wrote:

> Dear all,
> 
> I am observing "Segmentation fault" with below mentioned back-trace
> while playing video (loop back mode )and continuously pressing home
> button on target (which brings video screen to home screen of HMI).
> 
> Printing the locals shows null pointer deference (i.e. line 46, print
> elm->next,  wl_list_insert, /wayland-1.8.1/src/wayland-util.c:46  )
> 
> Am I hitting some known issue with wayland/weston? How should I debug
> this further and find the root cause if it is not known issue? Could
> you guys please provide input/suggestion on finding the root cause?
> 
> I am on wayland/weston 1.8.0 and using i.MX6/Linux3.14.28. Test
> application is based on gstreamer1.0 and uses wayland based
> “imxeglvivsink“ as video sink plug-in. Home button is a gpio mapped to
> KEY_HOME as standard keyboard and uses input stack as it is from
> wayland/weston and libinput.
> 
> 
> Backtrace:
> warning: Unable to find libthread_db matching inferior's thread
> library, thread debugging will not be available.
> warning: Unable to find libthread_db matching inferior's thread
> library, thread debugging will not be available.
> Core was generated by `./testVideoPlayer'.
> Program terminated with signal SIGSEGV, Segmentation fault.
> 
> #0  wl_list_insert (list=0x1, elm=0x1802660, elm at entry=0x16c) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-util.c:46
> 
> 46              elm->next = list->next;
> 
> (gdb) bt
> 
> #0  wl_list_insert (list=0x1, elm=0x1802660, elm at entry=0x16c) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-util.c:46
> 
> #1  0x75c412c8 in queue_event (len=1975783972, display=0x180116c) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-client.c:1122
> 
> #2  read_events (display=<optimized out>) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-client.c:1207
> 
> #3  0x75c42030 in wl_display_dispatch_queue
> (display=display at entry=0x76036800,  queue=queue at entry=0x760005a8) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-client.c:1579
> 
> #4  0x75c42290 in wl_display_roundtrip_queue (display=0x76036800,
> queue=0x760005a8) at
> /usr/src/debug/wayland/1.8.1-r0/wayland-1.8.1/src/wayland-client.c:982
> 
> #5  0x75d56cb4 in wl_egl_window_destroy (window=0x1801104) at
> gc_egl_platform.c:779
> 
> #6  0x75d7ab44 in gst_imx_egl_viv_sink_egl_platform_shutdown_window (
> platform=0x76016f00) at ../src/eglvivsink/egl_platform_wayland.c:990
> 
> #7  0x75d77e68 in gst_imx_egl_viv_sink_gles2_renderer_thread (
> thread_data=<optimized out>) at ../src/eglvivsink/gles2_renderer.c:227

Hi,

this looks very much like a threading issue in gst imx egl viv sink or
perhaps in the proprietary EGL implementation. Being random instead of
deterministically every time you press the button also hints to a race.

Note, that the code you are looking at is not Weston, it is some
application. I don't think this has anything to do with Weston or
Wayland really...

Unless this happens to be the case of multiple threads racing between
setting up queues and listeners for a wl_callback vs. receiving and
dispatching events: https://bugs.freedesktop.org/show_bug.cgi?id=91768

However, there are things that make looking into your issue very
difficult for upstream:
- old weston and wayland
- gstreamer sink written for a proprietary software platform
- proprietary EGL implementation
- use of IVI
- use of applications we cannot have the sources for (I presume)

IOW, it doesn't look like there would be any way for us to reproduce
the issue to have a look into.


Thanks,
pq
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