Hard lock in mutex on seek

Tue Nov 1 00:05:00 UTC 2022

Folks:

Running 1.20.4 on Ubuntu 22.04, my (python) code seeks:

Oct 27 07:27:55 player0 python3[7546]: set_seek_and_rate 20849000000000ns
2022-10-27T07:27:55.185108-07:00
An hour or two later I noted that it was hard hung.  Attaching to python3
using gdb, the stack trace looks like below. This required a power cycle,
as shutdown or kill -9 the process would not work. This is VERY
intermittent - first time I've seen in months. HOWEVER, since this is
intended to be mostly unattended, it worries me.

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
futex_wait (private=0, expected=2, futex_word=0x555c97ea0cf0) at
../sysdeps/nptl/futex-internal.h:146
146 ../sysdeps/nptl/futex-internal.h: No such file or directory.
(gdb) bt

*#0  futex_wait (private=0, expected=2, futex_word=0x555c97ea0cf0) at
../sysdeps/nptl/futex-internal.h:146#1  __GI___lll_lock_wait
(futex=futex at entry=0x555c97ea0cf0, private=0) at ./nptl/lowlevellock.c:49#2
 0x00007faad55a70dd in lll_mutex_lock_optimized (mutex=0x555c97ea0cf0) at
./nptl/pthread_mutex_lock.c:48#3  ___pthread_mutex_lock
(mutex=0x555c97ea0cf0) at ./nptl/pthread_mutex_lock.c:128#4
 0x00007faad3045736 in gst_element_send_event (element=0x555c97f54110,
event=0x7faa8c0c81d0) at ../subprojects/gstreamer/gst/gstelement.c:1980*#5
 0x00007faad3988e2e in  () at /lib/x86_64-linux-gnu/libffi.so.8
#6  0x00007faad3985493 in  () at /lib/x86_64-linux-gnu/libffi.so.8
#7  0x00007faad3b70722 in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#8  0x00007faad3b6e826 in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#9  0x00007faad3b6ea7d in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#10 0x0000555c956fe3bb in _PyObject_MakeTpCall ()
#11 0x0000555c956f6f59 in _PyEval_EvalFrameDefault ()
#12 0x0000555c9570812c in _PyFunction_Vectorcall ()
#13 0x0000555c956f09e6 in _PyEval_EvalFrameDefault ()
#14 0x0000555c9570812c in _PyFunction_Vectorcall ()
#15 0x0000555c956f09e6 in _PyEval_EvalFrameDefault ()
#16 0x0000555c9570812c in _PyFunction_Vectorcall ()
#17 0x0000555c956f09e6 in _PyEval_EvalFrameDefault ()
#18 0x0000555c95715c5e in  ()
#19 0x00007faad3b7254f in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#20 0x00007faad39887ec in  () at /lib/x86_64-linux-gnu/libffi.so.8
#21 0x00007faad3989050 in  () at /lib/x86_64-linux-gnu/libffi.so.8
#22 0x00007faad3a672a8 in  () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#23 0x00007faad3a66c24 in g_main_context_dispatch () at
/lib/x86_64-linux-gnu/libglib-2.0.so.0
#24 0x00007faad3abb6f8 in  () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#25 0x00007faad3a66293 in g_main_loop_run () at
/lib/x86_64-linux-gnu/libglib-2.0.so.0
#26 0x00007faad3988e2e in  () at /lib/x86_64-linux-gnu/libffi.so.8
#27 0x00007faad3985493 in  () at /lib/x86_64-linux-gnu/libffi.so.8
#28 0x00007faad3b70722 in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#29 0x00007faad3b6e826 in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#30 0x00007faad3b6ea7d in  () at /usr/lib/python3/dist-packages/gi/_
gi.cpython-310-x86_64-linux-gnu.so
#31 0x0000555c956fe3bb in _PyObject_MakeTpCall ()
#32 0x0000555c956f6f59 in _PyEval_EvalFrameDefault ()
#33 0x0000555c9570812c in _PyFunction_Vectorcall ()
#34 0x0000555c956f09e6 in _PyEval_EvalFrameDefault ()
#35 0x0000555c9570812c in _PyFunction_Vectorcall ()
#36 0x0000555c956f09e6 in _PyEval_EvalFrameDefault ()
#37 0x0000555c9570812c in _PyFunction_Vectorcall ()
#38 0x0000555c956f08a1 in _PyEval_EvalFrameDefault ()
#39 0x0000555c956ed026 in  ()
#40 0x0000555c957e3106 in PyEval_EvalCode ()
#41 0x0000555c9580fe18 in  ()
#42 0x0000555c95808c6b in  ()
#43 0x0000555c9580fb65 in  ()
#44 0x0000555c9580f048 in _PyRun_SimpleFileObject ()
#45 0x0000555c9580ed43 in _PyRun_AnyFileObject ()
#46 0x0000555c9580017e in Py_RunMain ()
#47 0x0000555c957d60dd in Py_BytesMain ()
#48 0x00007faad5538d90 in __libc_start_call_main
(main=main at entry=0x555c957d60a0,
argc=argc at entry=3, argv=argv at entry=0x7ffe8279e068) at
../sysdeps/nptl/libc_start_call_main.h:58
#49 0x00007faad5538e40 in __libc_start_main_impl (main=0x555c957d60a0,
argc=3, argv=0x7ffe8279e068, init=<optimized out>, fini=<optimized out>,
rtld_fini=<optimized out>, stack_end=0x7ffe8279e058)
    at ../csu/libc-start.c:392
#50 0x0000555c957d5fd5 in _start ()

Actual seek code:

        flags = Gst.SeekFlags.TRICKMODE | Gst.SeekFlags.KEY_UNIT |
Gst.SeekFlags.SNAP_NEAREST | Gst.SeekFlags.FLUSH

        seek_event = Gst.Event.new_seek(rate,
                                            Gst.Format.TIME,
                                            flags,
                                            Gst.SeekType.SET,
position_nanoseconds,
                                            Gst.SeekType.NONE, 0)

        if seek_event:
            self._player.send_event(seek_event)
        else:
            Gst.error("change rate failed")

Pipeline:

souphttpsrc location="http://localhost/foo.m3u8" !
         parsebin name=pb ! queue ! vaapih265dec !
         video/x-raw,format=P010_10LE !
         queue max-size-bytes=100663300 !
         kmssink connector-id=308 plane-id=31
    pb. ! queue ! fdkaacdec ! scaletempo ! volume volume=0.9 ! alsasink

Thoughts?
-Bill
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