Hello Martin,
On Sat, 23 Nov 2024 13:03:07 +0100,
Martin Pieuchot <m...@grenadille.net> wrote:
>
> Hello Kirill,
>
> On 22/11/24(Fri) 15:31, Kirill A. Korinsky wrote:
> > >Synopsis: deattach broken webcam leads to crash
>
> What do you mean by broken?
>
I mean that here no support of this webcam by some reason, so it is broken.
Probably bad wording, use not fully supported is better.
Anyway, I can read it by ffmpeg but not video:
~ $ video -q -f /dev/video1
video: /dev/video1 has no usable YUV encodings
~ $ ffmpeg -f v4l2 -list_formats all -i /dev/video1
ffmpeg version 4.4.5 Copyright (c) 2000-2024 the FFmpeg developers
built with OpenBSD clang version 16.0.6
configuration: --enable-shared --arch=amd64 --cc=cc --enable-debug
--disable-stripping --disable-indev=jack --disable-outdev=sdl2
--enable-fontconfig --enable-frei0r --enable-gpl --enable-ladspa
--enable-libaom --enable-libass --enable-libdav1d --enable-libfreetype
--enable-libfribidi --enable-libgsm --enable-libmp3lame --enable-libopus
--enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis
--enable-libvpx --enable-libx264 --enable-libx265 --enable-libxml2
--enable-libxvid --enable-libzimg --enable-nonfree --enable-openssl
--enable-libvidstab --extra-cflags='-I/usr/local/include -I/usr/X11R6/include'
--extra-libs='-L/usr/local/lib -L/usr/X11R6/lib' --extra-ldsoflags=
--mandir=/usr/local/man --objcc=/usr/bin/false --optflags='-O2 -pipe -g
-Wno-redundant-decls'
libavutil 56. 70.100 / 56. 70.100
libavcodec 58.134.100 / 58.134.100
libavformat 58. 76.100 / 58. 76.100
libavdevice 58. 13.100 / 58. 13.100
libavfilter 7.110.100 / 7.110.100
libswscale 5. 9.100 / 5. 9.100
libswresample 3. 9.100 / 3. 9.100
libpostproc 55. 9.100 / 55. 9.100
[video4linux2,v4l2 @ 0xc1be02d2800] Compressed: mjpeg :
MJPEG : 640x360 960x540 1280x720 1920x1080
/dev/video1: Immediate exit requested
~ $
Thus, when I try to use ffplay, it doesn't create a X11 window, instead it
complains like this:
[video4linux2,v4l2 @ 0x7224f2ce000] ioctl(VIDIOC_DQBUF): Invalid
argument
[video4linux2,v4l2 @ 0x7224f2ce000] Could not find codec parameters for
stream 0 (Video: mjpeg, none(bt470bg/unknown/unknown), 1920x1080): unspecified
pixel format
Consider increasing the value for the 'analyzeduration' (0) and
'probesize' (5000000) options
Input #0, video4linux2,v4l2, from '/dev/video1':
Duration: N/A, bitrate: N/A
Stream #0:0: Video: mjpeg, none(bt470bg/unknown/unknown), 1920x1080,
30 fps, 30 tbr, 1000k tbn, 1000k tbc
[video4linux2,v4l2 @ 0x7224f2ce000] ioctl(VIDIOC_DQBUF): Invalid
argument
[video4linux2,v4l2 @ 0x7224f2ce000] ioctl(VIDIOC_DQBUF): Invalid
argument
> > and it is frozen. I can't kill the process that leads to:
>
> Where is it frozen? On which sleep channel is ffplay sleeping? Can you
> enter ddb and get a trace of the ffplay process?
>
When ffplay is complaining ioctl(VIDIOC_DQBUF): Invalid argument, it creates
a few threads and everything works. When I press C-c on terminal or use
pkill -KILL ffplay nothing happens, but ffplay changes its state via ps from
~ $ ps aux | grep fplay
catap 20332 0.8 0.3 35204 53348 p2 S+ 2:05PM 0:00.51
ffplay -f v4l2 -i /dev/video1
catap 77165 0.0 0.0 796 1376 p4 S+p 2:05PM 0:00.01 grep
fplay
~ $
into
$ ps aux | grep ffplay
catap 20332 0.0 0.3 29280 47628 p2 RE+/2 2:05PM 0:00.63
(ffplay)
catap 97615 0.0 0.0 100 360 C0 R+/2 2:07PM 0:00.00 grep
ffplay
$
and there is no ffplay processes by ps in ddb anymore. I see only uvideo1
which has stacktrace:
ddb{1}> tr /t 0t393427
sleep_finish(0,1) at sleep_finish+0x17f
usbd_transfer(fffffdb461bb4c08) at usbd_transfer+0x275
uvideo_vs_start_bulk_thread(ffff800001b25000) at
uvideo_vs_start_bulk_thread+0x7e
end trace frame: 0x0, count: -3
ddb{1}>
and when I deattach the webcam from the machine, it crashes with stacktrace:
uvm_fault(0xfffffdb32e87f840, 0x3f, 0, 2) -> e
kernel: page fault trap, code=2
Stopped at usbd_close_pipe+0x91: movq %rcx,0x40(%rax)
TID PID UID PRFLAGS PFLAGS CPU COMMAND
420740 59811 1000 0x100002 0 0 xconsole
421818 10645 0 0x100000 0x80 3 hotplugd
205493 61124 0 0x14000 0x200 1 reaper
usbd_close_pipe(ffff800001c99000) at usbd_close_pipe+0x91
uvideo_close(ffff8000019bf000) at uvideo_close+0x57
videoclose(2c81,3,2000,ffff80004d2c16c8) at videoclose+0x63
spec_close(ffff80004bf56488) at spec_close+0x107
VOP_CLOSE(fffffdd4518e6e78,3,fffffdd3e18fe480,ffff80004d2c16c8) at
VOP_CLOSE+0x59
vn_closefile(fffffdd825a0edb58,ffff80004d2c16c8) at vn_closefile+0xaf
fdrop(fffffdd825a0edb58,ffff80004d2c16c8) at fdrop+0xa5
closef(fffffdd825a0edb58,ffff80004d2c16c8) at closef+0xaf
fdfree(ffff80004d2c16c8) at fdfree+0xa6
exit1(ffff80004d2c16c8,7b,0,1) at exit1+0x29b
sys_exit(ffff80004d2c16c8,ffff80004bf56780,ffff80004bf56f80) at
sys_exit+0x1a
syscall(ffff80004bf56780) at syscall+0x5e7
Xsyscall() at Xsyscall+0x128
end of kernel
end trace frame: 0x761dc4ff9130, count: 2
https://www.openbsd.org/ddb.html describes the minimum info required in
bug
reports. Insufficient info makes it difficult to find and fix bugs.
ddb(2)>
Here, I double-checked the traces and it shouldn't contain any typos/errors.
Also, if I wait a few minutes after C-c or kill ffpplay, I can deattach the
webcam without crashing, and the ffplay process just disappears.
--
wbr, Kirill
