Bug 290178 – [GStreamer] ASSERT triggered when attempting a seek on a paused pipeline playing an http URI

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Nikolas Zimmermann]

Created attachment 474669 [details]
Backtraces for all threads when WPEProcess hung

Visited https://www.wpewebkit.org using MiniBrowser + new API this morning, with a recent build.

I clicked on the button to playback the video, noting happened, I clicked another time, video started played for a few seconds, then restarted from scratch and played normal.
I closed MiniBrowser, retried and caught this assertion:

/host/home/nzimmermann/Software/GitRepositories/WebKit/Source/WTF/wtf/linux/RealTimeThreads.cpp(224) : void WTF::RealTimeThreads::realTimeKitMakeThreadRealTime(uint64_t, uint64_t, uint32_t)
ASSERTION FAILED: GST_ELEMENT(baseSrc)->current_state < GST_STATE_PAUSED || GST_ELEMENT(baseSrc)->current_state == GST_STATE_PLAYING || GST_PAD_IS_FLUSHING(baseSrc->srcpad)
/host/home/nzimmermann/Software/GitRepositories/WebKit/Source/WebCore/platform/graphics/gstreamer/WebKitWebSourceGStreamer.cpp(748) : gboolean webKitWebSrcDoSeek(GstBaseSrc *, GstSegment *)
1   0x71b55e55c6c8 webKitWebSrcDoSeek(_GstBaseSrc*, _GstSegment*)
2   0x71b5502f9a59 gst_base_src_perform_seek
3   0x71b55e55cd73 webKitWebSrcEvent(_GstBaseSrc*, _GstEvent*)
4   0x71b5502f5fe5 gst_base_src_event
5   0x71b553920ebd gst_pad_send_event_unchecked
6   0x71b553921544 gst_pad_push_event_unchecked
7   0x71b55392b0a5 gst_pad_push_event
8   0x71b553920ebd gst_pad_send_event_unchecked
9   0x71b553921544 gst_pad_push_event_unchecked
10  0x71b55392b0a5 gst_pad_push_event
...

On another try the WebProcess was just hanging, I attached gdb to the WebProcess and obtained a bt of all threads (see attachment).

[Philippe Normand]

Well... it seems there are 2 issues:

1. the failed assert (which should have triggered a crash)... do you have a coredump for this? It would be interesting to know which condition fails
2. a deadlock (the backtrace currently attached to this bug), likely between thread 1 (which attempts to aquire the basesrc pad mutex lock) and thread 37 (which likely has the lock acquired already)

I cannot reproduce any of those issues here.

[Nikolas Zimmermann]

I don't have a coredump right now, but will try to capture one, if it happens again.

[Philippe Normand]

(gdb) bt
#0  0x00007f5c64704949 in WTFCrash () at /var/home/phil/WebKit/WebKitBuild/WPE/Release/lib/libWPEWebKit-2.0.so.1
#1  0x00007f5c61841c9b in WTFCrashWithInfo(int, char const*, char const*, int) () at /var/home/phil/WebKit/WebKitBuild/WPE/Release/lib/libWPEWebKit-2.0.so.1
#2  0x00007f5c67624f80 in webKitWebSrcDoSeek(_GstBaseSrc*, _GstSegment*) () at /var/home/phil/WebKit/WebKitBuild/WPE/Release/lib/libWPEWebKit-2.0.so.1
#3  0x00007f5c59856f9d in gst_base_src_do_seek (src=0x8aade50 [WebKitWebSrc|source], segment=0x7f5a7a7fb000) at ../gstreamer/subprojects/gstreamer/libs/gst/base/gstbasesrc.c:1457
#4  gst_base_src_perform_seek (src=0x8aade50 [WebKitWebSrc|source], event=<optimized out>, unlock=1) at ../gstreamer/subprojects/gstreamer/libs/gst/base/gstbasesrc.c:1810
#5  0x00007f5c676253cc in webKitWebSrcEvent(_GstBaseSrc*, _GstEvent*) () at /var/home/phil/WebKit/WebKitBuild/WPE/Release/lib/libWPEWebKit-2.0.so.1
#6  0x00007f5c59853291 in gst_base_src_event (pad=<optimized out>, parent=0x8aade50 [WebKitWebSrc|source], event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/libs/gst/base/gstbasesrc.c:2188
#7  0x00007f5c5cbb645b in gst_pad_send_event_unchecked (pad=pad@entry=0x8aae190 [GstPad|src], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>, type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:6071
#8  0x00007f5c5cbb6e5c in gst_pad_push_event_unchecked (pad=pad@entry=0x8ab05d0 [GstPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>, type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5666
#9  0x00007f5c5cbc0755 in gst_pad_push_event (pad=0x8ab05d0 [GstPad|sink], event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5812
#10 0x00007f5c5cbb645b in gst_pad_send_event_unchecked (pad=pad@entry=0x8ab09c0 [GstPad|src], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>, type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:6071
#11 0x00007f5c5cbb6e5c in gst_pad_push_event_unchecked (pad=pad@entry=0x7f5ad403f850 [GstPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>,
    type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5666
#12 0x00007f5c5cbc0755 in gst_pad_push_event (pad=0x7f5ad403f850 [GstPad|sink], event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5812
#13 0x00007f5c5cbb645b in gst_pad_send_event_unchecked (pad=pad@entry=0x7f5ad403fbe0 [GstPad|src], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>, type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:6071
#14 0x00007f5c5cbb6e5c in gst_pad_push_event_unchecked (pad=pad@entry=0x7f5ad403bbb0 [GstGhostPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>,
    type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5666
#15 0x00007f5c5cbc0755 in gst_pad_push_event (pad=pad@entry=0x7f5ad403bbb0 [GstGhostPad|sink], event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5812
#16 0x00007f5c5cbc0c61 in event_forward_func (pad=0x7f5ad403bbb0 [GstGhostPad|sink], data=0x7f5a7a7fb6e0) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:3165
#17 0x00007f5c5cbbcbdb in gst_pad_forward (pad=pad@entry=0x7f5ad403bf90 [GstProxyPad|proxypad7], forward=forward@entry=0x7f5c5cbc0ba0 <event_forward_func>, user_data=user_data@entry=0x7f5a7a7fb6e0)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:3119
#18 0x00007f5c5cbbccd5 in gst_pad_event_default (pad=0x7f5ad403bf90 [GstProxyPad|proxypad7], parent=<optimized out>, event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:3216
#19 0x00007f5c5cbb645b in gst_pad_send_event_unchecked (pad=pad@entry=0x7f5ad403bf90 [GstProxyPad|proxypad7], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>,
    type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:6071
#20 0x00007f5c5cbb6e5c in gst_pad_push_event_unchecked (pad=pad@entry=0x7f5ad403a250 [GstPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>,
    type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5666
#21 0x00007f5c5cbc0755 in gst_pad_push_event (pad=0x7f5ad403a250 [GstPad|sink], event=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5812
#22 0x00007f5c5cbb645b in gst_pad_send_event_unchecked (pad=pad@entry=0x7f5ad403a630 [GstPad|src], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>, type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM)
    at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:6071
#23 0x00007f5c5cbb6e5c in gst_pad_push_event_unchecked (pad=pad@entry=0x7f5a6c17a020 [GstPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent], type=<optimized out>,
    type@entry=GST_PAD_PROBE_TYPE_EVENT_UPSTREAM) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5666
#24 0x00007f5c5cbc0755 in gst_pad_push_event (pad=0x7f5a6c17a020 [GstPad|sink], event=event@entry=0x7f5a6c003550 [GstEvent]) at ../gstreamer/subprojects/gstreamer/gst/gstpad.c:5812
#25 0x00007f5a94100f32 in gst_ogg_demux_loop_push (ogg=0x7f5a6c179b80 [GstOggDemux|oggdemux0]) at ../gstreamer/subprojects/gst-plugins-base/ext/ogg/gstoggdemux.c:5095
#26 0x00007f5c5cdf6862 in g_thread_proxy (data=0x7f5a6c17a8f0) at ../glib/gthread.c:893
#27 0x00007f5c5c5911d4 in start_thread (arg=<optimized out>) at pthread_create.c:448
#28 0x00007f5c5c613b14 in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:100
(gdb) f 3
(gdb) p *src
$1 = {element = {object = {object = {g_type_instance = {g_class = 0x8952900 [g_type: WebKitWebSrc/GstPushSrc/GstBaseSrc/GstElement/GstObject/GInitiallyUnowned]}, ref_count = 5, qdata = 0x8ab3890}, lock = {
        p = 0x0, i = {0, 0}}, name = 0x8aae3e0 "source", parent = 0x8aa7e80 [GstURIDecodeBin|uridecodebin0], flags = 32834, control_bindings = 0x0, control_rate = 100000000, last_sync = 18446744073709551615,
      _gst_reserved = 0x0}, state_lock = {p = 0x8aacf40, i = {0, 0}}, state_cond = {p = 0x0, i = {20, 0}}, state_cookie = 10, target_state = GST_STATE_PAUSED, current_state = GST_STATE_PAUSED,
    next_state = GST_STATE_VOID_PENDING, pending_state = GST_STATE_VOID_PENDING, last_return = GST_STATE_CHANGE_SUCCESS, bus = 0x894e6c0 [GstBus|bus21], clock = 0x8a84ee0 [GstAudioClock|GstPulseSinkClock],
    base_time = 0 [+0:00:00.000000000], start_time = 451000 [0:00:00.000451000], numpads = 1, pads = 0x8aa3da0 = {0x8aae190}, numsrcpads = 1, srcpads = 0x8aacf70 = {0x8aae190}, numsinkpads = 0, sinkpads = 0x0,
    pads_cookie = 1, contexts = 0x7f5ac8007920 = {0x7f5ad40065c0}, _gst_reserved = {0x0, 0x0, 0x0}}, srcpad = 0x8aae190 [GstPad|src], live_lock = {p = 0x0, i = {0, 0}}, live_cond = {p = 0x0, i = {8, 0}},
  is_live = 0, live_running = 0, blocksize = 8192, can_activate_push = 1, random_access = 0, clock_id = 0x0, segment = {flags = GST_SEGMENT_FLAG_SEGMENT, rate = 1, applied_rate = 1, format = GST_FORMAT_BYTES,
    base = 173788, offset = 0, start = 0, stop = 18446744073709551615, time = 0, position = 40960, duration = 1607177, _gst_reserved = {0x0, 0x0, 0x0, 0x0}}, need_newsegment = 0, num_buffers = -1,
  num_buffers_left = -1, typefind = 0, running = 0, pending_seek = 0x0, priv = 0x8aadd70, _gst_reserved = {0x0 <repeats 20 times>}}

[Philippe Normand]

Pull request: https://github.com/WebKit/WebKit/pull/48113

[EWS]

Committed 297575@main (464f2b6d7494): <https://commits.webkit.org/297575@main>

Reviewed commits have been landed. Closing PR #48113 and removing active labels.

[Radar WebKit Bug Importer]

<rdar://problem/156127708>