Bug 766703 – glvideomixer: Using an invalid, already destroyed context

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Bug 766703 - glvideomixer: Using an invalid, already destroyed context


Summary:	glvideomixer: Using an invalid, already destroyed context


Status:	RESOLVED FIXED

Product:	GStreamer
Classification:	Platform
Component:	gst-plugins-bad
Version:	git master
Hardware:	Other Linux

Importance:	Normal blocker
Target Milestone:	1.9.1
Assigned To:	GStreamer Maintainers
QA Contact:	GStreamer Maintainers

URL:
Whiteboard:

Depends on:
Blocks:

Reported:	2016-05-20 09:15 UTC by Sebastian Dröge (slomo)
Modified:	2016-05-25 08:31 UTC

See Also:
GNOME target:	---
GNOME version:	---

Description Sebastian Dröge (slomo) 2016-05-20 09:15:00 UTC

GST_VALIDATE_SCENARIOS_PATH=/home/slomo/Projects/gstreamer/head/gst-devtools/validate/data/scenarios: GST_GL_XINITTHREADS=1 DISPLAY=:0 GST_VALIDATE_SCENARIO=play_15s /home/slomo/Projects/gstreamer/head/gst-devtools/validate/tools/gst-validate-1.0-debug  glvideomixer sink_1::alpha=0.5 sink_1::xpos=50 sink_1::ypos=50 name=_mixer !  deinterlace ! videoconvert ! 'fakesink' videotestsrc pattern=snow timestamp-offset=3000000000 ! 'video/x-raw,format=AYUV,width=640,height=480,framerate=(fraction)30/1' !  timeoverlay ! _mixer. videotestsrc pattern=smpte ! 'video/x-raw,format=AYUV,width=800,height=600,framerate=(fraction)10/1' ! timeoverlay ! _mixer.

This fails with assertions every now and then:
0:00:00.405870420 22018 0x7fffdc004000 ERROR               validate gst-validate-reporter.c:176:gst_validate_report_valist: <pipeline0> 2272 (critical) : g-log: We got a g_log critical issue : g_object_ref: assertion 'object->ref_count > 0' failed

+ Trace 236267

#6 gst_gl_buffer_pool_new
at gstglbufferpool.c line 300
#0 g_logv
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmessages.c line 325
#1 g_logv
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmessages.c line 1080
#2 g_log
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmessages.c line 1119
#3 g_return_if_fail_warning
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gmessages.c line 1134
#4 g_object_ref
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./gobject/gobject.c line 3050
#5 gst_object_ref
at gstobject.c line 256
#6 gst_gl_buffer_pool_new
at gstglbufferpool.c line 300
#7 gst_gl_mixer_propose_allocation
at gstglmixer.c line 157
#8 gst_gl_video_mixer_propose_allocation
at gstglvideomixer.c line 940
#9 gst_gl_base_mixer_sink_query
at gstglbasemixer.c line 287
#10 gst_gl_mixer_sink_query
at gstglmixer.c line 300
#11 gst_validate_pad_monitor_query_func
at gst-validate-pad-monitor.c line 2198
#12 gst_pad_query
at gstpad.c line 3940
#13 gst_pad_peer_query
at gstpad.c line 4072
#14 gst_base_transform_setcaps
at gstbasetransform.c line 1003
#15 gst_base_transform_setcaps
at gstbasetransform.c line 1392
#16 gst_base_transform_sink_eventfunc
at gstbasetransform.c line 1939
#17 gst_validate_pad_monitor_downstream_event_check
at gst-validate-pad-monitor.c line 1830
#18 gst_validate_pad_monitor_sink_event_full_func
at gst-validate-pad-monitor.c line 2154
#19 gst_validate_pad_monitor_sink_event_func
at gst-validate-pad-monitor.c line 2167
#20 gst_pad_send_event_unchecked
at gstpad.c line 5594
#21 gst_pad_push_event_unchecked
at gstpad.c line 5252
#22 push_sticky
at gstpad.c line 3797
#23 events_foreach
at gstpad.c line 603
#24 gst_pad_push_event
at gstpad.c line 3854
#25 gst_pad_push_event
at gstpad.c line 5383
#26 gst_base_transform_setcaps
at ../../../gst/gstcompat.h line 58
#27 gst_base_transform_setcaps
at gstbasetransform.c line 1387
#28 gst_base_transform_sink_eventfunc
at gstbasetransform.c line 1939
#29 gst_validate_pad_monitor_downstream_event_check
at gst-validate-pad-monitor.c line 1830
#30 gst_validate_pad_monitor_sink_event_full_func
at gst-validate-pad-monitor.c line 2154
#31 gst_validate_pad_monitor_sink_event_func
at gst-validate-pad-monitor.c line 2167
#32 gst_pad_send_event_unchecked
at gstpad.c line 5594
#33 gst_pad_push_event_unchecked
at gstpad.c line 5252
#34 push_sticky
at gstpad.c line 3797
#35 events_foreach
at gstpad.c line 603
#36 gst_pad_push_event
at gstpad.c line 3854
#37 gst_pad_push_event
at gstpad.c line 5383
#38 event_forward_func
at gstpad.c line 2984
#39 gst_pad_forward
at gstpad.c line 2938
#40 gst_pad_event_default
at gstpad.c line 3035
#41 gst_pad_send_event_unchecked
at gstpad.c line 5594
#42 gst_pad_push_event_unchecked
at gstpad.c line 5252
#43 push_sticky
at gstpad.c line 3797
#44 events_foreach
at gstpad.c line 603
#45 gst_pad_push_event
at gstpad.c line 3854
#46 gst_pad_push_event
at gstpad.c line 5383
#47 gst_base_text_overlay_negotiate
at /home/slomo/Projects/gstreamer/head/gstreamer/gst/gstcompat.h line 58
#48 gst_base_text_overlay_negotiate
at gstbasetextoverlay.c line 913
#49 gst_base_text_overlay_video_event
at gstbasetextoverlay.c line 969
#50 gst_base_text_overlay_video_event
at gstbasetextoverlay.c line 2415
#51 gst_validate_pad_monitor_downstream_event_check
at gst-validate-pad-monitor.c line 1830
#52 gst_validate_pad_monitor_sink_event_full_func
at gst-validate-pad-monitor.c line 2154
#53 gst_validate_pad_monitor_sink_event_func
at gst-validate-pad-monitor.c line 2167
#54 gst_pad_send_event_unchecked
at gstpad.c line 5594
#55 gst_pad_push_event_unchecked
at gstpad.c line 5252
#56 push_sticky
at gstpad.c line 3797
#57 events_foreach
at gstpad.c line 603
#58 gst_pad_push_event
at gstpad.c line 3854
#59 gst_pad_push_event
at gstpad.c line 5383
#60 gst_base_transform_setcaps
at ../../../gst/gstcompat.h line 58
#61 gst_base_transform_setcaps
at gstbasetransform.c line 1387
#62 gst_base_transform_sink_eventfunc
at gstbasetransform.c line 1939
#63 gst_capsfilter_sink_event
at gstcapsfilter.c line 521
#64 gst_validate_pad_monitor_downstream_event_check
at gst-validate-pad-monitor.c line 1830
#65 gst_validate_pad_monitor_sink_event_full_func
at gst-validate-pad-monitor.c line 2154
#66 gst_validate_pad_monitor_sink_event_func
at gst-validate-pad-monitor.c line 2167
#67 gst_pad_send_event_unchecked
at gstpad.c line 5594
#68 gst_pad_push_event_unchecked
at gstpad.c line 5252
#69 push_sticky
at gstpad.c line 3797
#70 events_foreach
at gstpad.c line 603
#71 gst_pad_push_event
at gstpad.c line 3854
#72 gst_pad_push_event
at gstpad.c line 5383
#73 gst_base_src_set_caps
at gstbasesrc.c line 924
#74 gst_base_src_default_negotiate
at gstbasesrc.c line 3231
#75 gst_base_src_loop
at gstbasesrc.c line 3271
#76 gst_base_src_loop
at gstbasesrc.c line 2697
#77 gst_task_func
at gsttask.c line 332
#78 g_thread_pool_thread_proxy
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gthreadpool.c line 307
#79 g_thread_proxy
at /build/glib2.0-wnDt2X/glib2.0-2.48.1/./glib/gthread.c line 780
#80 start_thread
at pthread_create.c line 334
#81 clone
at ../sysdeps/unix/sysv/linux/x86_64/clone.S line 109

Comment 1 Sebastian Dröge (slomo) 2016-05-21 07:03:32 UTC

The only GL element here is glvideomixer, and nowhere in it I see any suspicious unreffing of the context. It might be inside libgstgl somewhere.

Comment 2 Matthew Waters (ystreet00) 2016-05-25 08:31:22 UTC

commit 061a157ef57df81dd1e87ae7a78cdcf94fd42be0
Author: Matthew Waters <matthew@centricular.com>
Date:   Tue May 24 23:39:27 2016 +1000

    glvideomixer: fix race retrieving the GL context from the display
    
    _get_gl_context() can be called concurrently from either propose_allocation() or
    decide_allocation().  If it so happens that this happens at the same time,
    the check for whether we already had a GL context was outside the lock.  Inside
    the lock and loop, the first thing that happens is that we unref the current GL
    context (if valid) as if there was a conflict adding it to the display.  If the
    timing was unlucky, subsequent use of the GL context would be referencing an
    already unreffed GL context object resulting in a critical:
    
    g_object_ref: assertion 'object->ref_count > 0' failed
    
    https://bugzilla.gnome.org/show_bug.cgi?id=766703