Classic confinement request for "Open Karaoke Producer"


I would like to ask “classic” confinement review for “Open Karaoke Producer” package. It uses python multiprocessing module, that needs to access /dev/shm but due to a unsolved bug/limitation (Python multiprocessing sem_open blocked in strict mode), it is not able to run in strict confinement. As it seems that this bug/limitation will not be solved soon, and all proposed workarounds do not fix this problem, I will need to create this package as classic in order to see it running in snap format.

Thanks for your attention.

we really need to figure out a way to get per-snap dev/shm support so that we’re not required to conform to strict naming requirements. @sergiusens you mentioned that layouts will fix this. they don’t. I tried layouts with a snap that cannot be fixed any other way, and it just complained that I’m not allowed to use layouts to mount anything at /dev/shm.

@jdstrand you mentioned it could work in a meeting we were in, but needed to confirm, mind looking into it?

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Hi there!

Any news on this? I am receiving emails from build system saying that the package is not accepted. Something I need to adjust on my side? I understand the implications, but as this is a limitation of snap, classic confinement is the only way to get the packages on store on cases like mine by now. :confused:

Thank you very much for your consideration.

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Please see Python multiprocessing sem_open blocked in strict mode. I believe @lucyllewy is working on a snapcraft-preload update too. Can you report back if this works for you?

Sure! As soon as the preload repository is updated, I will test it


Daniel’s PR is working with my package. Thanks!

The only thing is that it now shows the following warning (but it is not blocking functionality):

/snap/open-karaoke-producer/24/lib/python3.6/site-packages/joblib/ UserWarning: [Errno 13] Permission denied.  joblib will operate in serial mode
  warnings.warn('%s.  joblib will operate in serial mode' % (e,))
/snap/open-karaoke-producer/24/lib/python3.6/site-packages/numba/npyufunc/ UserWarning: Could not obtain multiprocessing lock due to OS level error: [Errno 13] Permission denied
A likely cause of this problem is '/dev/shm' is missing orread-only such that necessary semaphores cannot be written.
*** The responsibility of ensuring multiprocessing safe access to this initialization sequence/module import is deferred to the user! ***

Note that /dev/shm is supposed to be a tmpfs with 1777 permissions. Eg:

$ mount |grep shm
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
$ ls -ld /dev/shm
drwxrwxrwt 2 root root 40 Jan 22 15:14 /dev/shm