mythpreviewgen SEGFAULT

[Kenni Lund [kenni a kelu dot dk]]

I'm seeing mythpreviewgen segfaults more or less on a daily basis on 0.26-fixes. I'm attaching a backtrace extracted from a core dump together with the corresponding mythpreviewgen log file. The segfault was in LWP 26415.

I'll attach some more backtraces once I experience them.

Version: v0.26.0-112-g77259c5

[Kenni Lund [kenni a kelu dot dk]]

Well, that was easy...scrolling down the list of some of the recordings on my frontend, caused ~25 mythpreviewgen segfaults/coredumps in 2 minutes :) I've extracted and attached 10 backtraces.

[Raymond Wagner]

The segfaults are all occurring within the video decoding libraries. Is this something that should get passed upstream to FFmpeg?

[JYA]

please try with 0.27 and report if it's fixed

[JYA]

had another idea.. can you change the playback profile to set the maximum number of CPU to just 1?

[Kenni Lund [kenni a kelu dot dk]]

I upgraded to master on the 21st of August and it wasn't fixed in that checkout. I'll test with the playback setting on Monday.

[JYA]

can you provide more information about the type of codec used in those recordings.. and provide a sample of a file , long enough to try running mythpreviewgen on it and attempt to reproduce your problem.

thanks

[Kenni Lund [kenni a kelu dot dk]]

Hi Jya

The recordings are H.264 with AC-3 recorded with a HDHR from DVB-C. I've extracted a 30MB sample from one of the recordings which causes the crash. Running mythpreviewgen directly on the sample causes the crash as well:

mythpreviewgen --infile mythpreviewgen_crash_11452.mpg

You can download the sample from here (doesn't require login, just click Files->Download): ​https://docs.google.com/file/d/0B-_nZameGeN-ZkhCdUFGRlRfVVk/edit?usp=sharing

Unfortunately, I don't have access to a working frontend at the moment, so I'm unable to test with max. CPU set to 1.

[stuartm]

Kenni, can you try the attached patch?

[stuartm]

Possible fix

[Kenni Lund [kenni a kelu dot dk]]

Stuart, the patch from Lawrence fixes the issue. I don't get any segfaults, even when running mythpreviewgen against all of my 430 recordings :) Thanks..

(and thanks to you Jya for pinpointing the core issue).

[Lawrence Rust <lvr@…>]

In 6e62a3c601b93c6d9525cc503634350a965a5058/mythtv:

Player: Delete decoder after decoder thread stopped

It is important to delete the decoder in DecoderEnd? to ensure that any
threads allocated by the Ffmpeg decoder are stopped before the video
buffers are deallocated. If not then random crashes can be observed
when exiting playback of H264 encoded material if CPUs are > 1.

Fixes #11452

Signed-off-by: Lawrence Rust <lvr@…>
Signed-off-by: Stuart Morgan <smorgan@…>

[Lawrence Rust <lvr@…>]

In 4fed56abd73200615fab39b31aafc62c67d94145/mythtv:

Player: Delete decoder after decoder thread stopped

It is important to delete the decoder in DecoderEnd? to ensure that any
threads allocated by the Ffmpeg decoder are stopped before the video
buffers are deallocated. If not then random crashes can be observed
when exiting playback of H264 encoded material if CPUs are > 1.

Fixes #11452

Signed-off-by: Lawrence Rust <lvr@…>
Signed-off-by: Stuart Morgan <smorgan@…>
(cherry picked from commit 6e62a3c601b93c6d9525cc503634350a965a5058)