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[Michi Henning <michi.henning@xxxxxxxxxxxxx>]

Here is a reproducible test case.

$ system-image-cli -i
current build number: 229
device name: mako
channel: ubuntu-touch/devel-proposed/ubuntu
last update: 2015-06-18 07:16:41
version version: 229
version ubuntu: 20150618
version device: 20150529.1
version custom: 20150618

The code was built from this branch at revision 238:

https://code.launchpad.net/~michihenning/thumbnailer/no-download-for-
failure-cache-hit

The debian packages are:

http://s-jenkins.ubuntu-ci:8080/job/thumbnailer-devel-wily-armhf-ci/lastSuccessfulBuild/artifact/work/output/thumbnailer-common_1.4bzr238pkg0wily145-0ubuntu1_all.deb
http://s-jenkins.ubuntu-ci:8080/job/thumbnailer-devel-wily-armhf-ci/lastSuccessfulBuild/artifact/work/output/thumbnailer-service_1.4bzr238pkg0wily145-0ubuntu1_armhf.deb
http://s-jenkins.ubuntu-ci:8080/job/thumbnailer-devel-wily-armhf-ci/lastSuccessfulBuild/artifact/work/output/qtdeclarative5-ubuntu-thumbnailer0.1_1.4bzr238pkg0wily145-0ubuntu1_armhf.deb

To reproduce the problem, install the debs and untar the attached
archive into an empty directory somewhere.

Run top in another terminal.

Now, from within the video directory, run the following script:

#!/bin/sh
for i in video*.mp4
do
    /usr/lib/arm-linux-gnueabihf/thumbnailer/vs-thumb fd://0 $i.jpg <$i &
done
wait

This fires as many vs-thumb instances concurrently as there are video
files (see below).

It's possible that the script will terminate without error. (The fewer
videos there are, the more likely it is to succeed.) If it succeeds,
just try again.

Eventually, the script will not terminate, and top will show one or more
hung vs-thumb processes that are consuming 100% CPU each.

Here comes the good bit. (You may have to try this several times but,
eventually, you'll see the problem.)

>From another terminal, run

kill -9 <hung-vs-thumb-pid>

Quite often, it'll kill the process as it should. But, every now and
then, it doesn't. Instead, the hung vs-thumb keeps hanging around, still
consuming 100% CPU until, pretty much exactly 30 seconds later, it
exits.

So, the kill -9 doesn't kill until 30 seconds later in some cases.

While experimenting with all this, you will most likely also see this:

Error creating thumbnail: ThumbnailExtractor: change_state(): reading
async messages: GStreamer error: negotiation problem.

This error is unrelated and can be reproduced on the desktop by just
running a single vs-thumb at a time in a loop. On my Core i7, I get this
once every two-hundred iterations or so.

You will probably also see

(vs-thumb:26741): GLib-ERROR **:
/build/buildd/glib2.0-2.45.1/./glib/gmem.c:357: overflow allocating
4294967274*8 bytes

That happens when there are too many vs-thumb processes. It doesn't seem
to be happening with only four concurrent gstreamer processes. You can
show this by moving two of the videos out of the directory. However, the
allocation problem is *NOT* related to the signal issue. The signal
issue can be reproduced even when this allocation failure doesn't occur,
with only four concurrent vs-thumb processes.

The source code for vs-thumb is in the thumbnailer project, in src/vs-
thumb. There isn't a lot of code there (around 400 lines), so it's quite
easy to see what's going on.


** Attachment added: "videos.tar"
   https://bugs.launchpad.net/ubuntu/+source/gstreamer1.0/+bug/1466273/+attachment/4420242/+files/videos.tar

-- 
You received this bug notification because you are a member of Desktop
Packages, which is subscribed to gstreamer1.0 in Ubuntu.
https://bugs.launchpad.net/bugs/1466273

Title:
  gstreamer fails intermittently

Status in Thumbnail generator for all kinds of files:
  New
Status in gstreamer package in Ubuntu:
  New
Status in gstreamer1.0 package in Ubuntu:
  New

Bug description:
  gstreamer occasionally fails to extract a thumbnail from a video file.
  It's clearly a race condition because, almost all of the time, it
  succeeds. To reproduce:

  Check out the thumbnailer/devel branch at r217 and build it. Then:

  cd build/src/vs-thumb

  ./vs-thumb fd://0 ./x.jpg <../../../tests/media/testvideo.ogg

  Point a browser at the generated x.jpg file and check that the image
  was extracted correctly.

  Now run

  while ./vs-thumb fd://0 ./x.jpg <../../../tests/media/testvideo.ogg ;
  do :; done

  Within maybe a hundred iterations or so, I get:

  Error creating thumbnail: ThumbnailExtractor: change_state(): reading
  async messages: GStreamer error: negotiation problem.

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