[Buildd-tools-devel] Bug#489116: Bug#489116: schroot: possible race condition during chroot setup?

[Lucas Nussbaum]

On 04/07/08 at 00:07 +0200, Lucas Nussbaum wrote:
> On 03/07/08 at 20:13 +0100, Roger Leigh wrote:
> > Lucas Nussbaum <lucas at lucas-nussbaum.net> writes:
> > 
> > > I run several instances of sbuild+schroot in parallel. Sometimes, I run
> > > into the following error message:
> > > Build started at 20080703-0045
> > > ******************************************************************************
> > > Cannot create link /etc/mtab~
> > > Perhaps there is a stale lock file?
> > >
> > > E: lsid32-ba72d12e-d721-4f01-aa83-78ce46e9691c: Chroot setup failed: stage=setup-start
> > > Chroot setup failed
> > > Error creating schroot session: skipping zope-ldapmultiplugins
> > > ******************************************************************************
> > >
> > > Could this be caused by a race condition in schroot or sbuild ? I
> > > never ran into this when I was running only one instance at a time.
> > 
> > While it is possible that a race condition exists, I can't find any
> > reference to "Cannot create link" or /etc/mtab in either the schroot
> > or sbuild sources.  I don't know where that message is coming from.
> > 
> > Which chroot type are you using with sbuild/schroot?  The locking can
> > vary between the different types, and some (e.g. plain, directory)
> > shouldn't be used if you are running sbuild in parallel, though sbuild
> > itself should do its own locking in this case and catch the problem.
> 
> I'm using file chroots.

It seems that this is caused by mount failing to lock /etc/mtab (because
another build process is already mounting an FS). mount
returns 16 in that case according to mount(8). I think that it would
make sense to retry mounting once or twice in that case.

This occured 6 times during my full archive rebuild today.
-- 
| Lucas Nussbaum
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