[FFmpeg-trac] #3169(avdevice:new): x11grab leaks shared memory if X server shuts down

[FFmpeg]

#3169: x11grab leaks shared memory if X server shuts down
--------------------------------------+------------------------------------
             Reporter:  levialliance  |                    Owner:
                 Type:  defect        |                   Status:  new
             Priority:  normal        |                Component:  avdevice
              Version:  git-master    |               Resolution:
             Keywords:  x11grab       |               Blocked By:
             Blocking:                |  Reproduced by developer:  0
Analyzed by developer:  0             |
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Comment (by levialliance):

 Extra av_log debugging output with SIGINT:
 {{{
 Press [q] to stop, [?] for help
 video:25920kB audio:0kB subtitle:0 global headers:0kB muxing overhead
 0.000000%
 fmpeg_cleanup() called
     avformat_close_input() called
       x11grab_read_close() called
       x11grab_read_close() done
     avformat_close_input() done
 Received signal 2: terminating.
 ffmpeg_cleanup() done.
 }}}

 With X shutdown:
 {{{
 Press [q] to stop, [?] for help
 XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server
 ":0"kbits/s
       after 339 requests (339 known processed) with 0 events remaining.
 }}}


 I created a partial solution that has been tested on linux here:
 https://github.com/levic/FFmpeg/compare/FFmpeg:master...master
 It's only a partial solution because while it solves SIGKILL/X disconnect
 for x11grab, if any other filters/input devices need to be cleanly shut
 down they still won't be if x11grab encounters an X disconnect.

 On linux and freebsd, you can mark the segment for deletion while
 processes are still attached and it will automatically clean up when the
 attached process count goes to zero.
 http://linux.die.net/man/2/shmctl
 http://www.freebsd.org/cgi/man.cgi?query=shmctl&sektion=2

 Unfortunately posix & solaris say nothing along these lines and may delete
 the segment immediately (or at least prevent X from attaching to it)
 http://docs.oracle.com/cd/E19109-01/tsolaris8/835-8003/6ruu1b0qp/index.html
 http://pubs.opengroup.org/onlinepubs/007904975/functions/shmctl.html
 http://unix.derkeiler.com/Newsgroups/comp.unix.programmer/2005-04/0599.html

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Ticket URL: <https://trac.ffmpeg.org/ticket/3169#comment:2>
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