Re: [PATCH] rootfs: Use separate mounts lock file

[Jan Kiszka <jan.kiszka@siemens.com>]

On 26.07.21 17:46, Baurzhan Ismagulov wrote:
> On Mon, Jul 26, 2021 at 05:44:26PM +0300, Anton Mikanovich wrote:
>>> Definitely a good catch, but I'm still wrapping my head around it. We
>>> either have really separated rootfs'es here so that separated lock files
>>> are fine, or we rather want rootfs_do_mounts to be locked against
>>> buildchroot_do_mounts as well. At least conceptually, even if they well
>>> never run in parallel in practice. In that case, MOUNT_LOCKFILE in
>>> rootfs.bbclass should be made a weak assignment, to clarify that
>>> buildchroot.bbclass will win, irrespective of any ordering.
>>>
>> We've performed additional checking and testing of parallel
>> mounting/unmounting and didn't find any issues there.
>> So I'm pretty sure this should be merged.
> 
> To explain the background, we couldn't identify any resource sharing in any
> combination of buildchroot and rootfses, so a separate lock has been recently
> introduced in e438c8f6 "rootfs: Unmount rootfs mounts if not needed".
> 
> This didn't work correctly, as described in the commit message.
> 
> Regarding *_do_mounts, they would need to be serialized if mount(8) would have
> unlocked shared resources. At least a simple script running 100 mounts and
> umounts in parallel didn't reveal any issues.
> 

OK, then let's document that in the commit and merge it.

Jan

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