On Tue, 4 Nov 2003, Matthew Mitchell wrote:
> On Tue, 2003-11-04 at 11:02, H. Peter Anvin wrote:
> > Matthew Mitchell wrote:
> > > Hello,
> > >
> > > On some SMP processing nodes we have in our cluster we are noticing the
> > > following odd behavior. It seems like there might be a race condition
> > > somewhere in automount that results in the same (in this case NFS)
> > > device mounted twice on the same mountpoint.
> > >
> > > In our case we have a (closed-source, vendor provided) data processing
> > > app that runs 2-4 processes at a time on each of these nodes. The
> > > processes communicate via MPI. What ends up happening is that each of
> > > them tries to read data from these NFS-mounted volumes at exactly the
> > > same time, and sometimes (about one node out of every 10) we get unlucky
> > > and the disk gets double-mounted.
> > >
> > > Here is the entry from the messages file where the disks are getting
> > > mounted:
> > > Nov 2 16:52:53 fir32 automount[674]: attempting to mount entry
> > > /etvf/data0
> > > Nov 2 16:52:53 fir32 automount[674]: attempting to mount entry
> > > /etvf/data0
> > >
> > > (Yes, there are two of them.)
> > >
> >
> > This happens because mount silently changed behaviour -- autofs relies
> > on mount only allowing one thing to be mounted on each mount point, but
> > that was suddenly changed without warning.
>
> Yes, I know that mount can do that now. But automount is spawning the
> second mount before the first one completes, no? Still seems like there
> should be some sort of mutual exclusion around the lookup_mount call. I
> realize our workload is kind of funny in that the processes effectively
> _try_ to synchronize their automount request.
>
> Has any of this changed in the 4.0-pre autofs? I haven't read through
> its source yet.
Yep. If you are willing, try the latest autofs-4.1.0-beta.
--
,-._|\ Ian Kent
/ \ Perth, Western Australia
*_.--._/ E-mail: [EMAIL PROTECTED]
v Web: http://themaw.net/
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