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Re: [Linux-cluster] GFS2 processes getting stuck in WCHAN=dlm_posix_lock



This sounds like a memory problem from the mail app or OS that runs into the cluster software. Trace running memory heaps in the dump.

On Fri, Oct 30, 2009 at 6:27 PM, Allen Belletti <allen isye gatech edu> wrote:
Hi All,

As I've mentioned before, I'm running a two-node clustered mail server on GFS2 (with RHEL 5.4)  Nearly all of the time, everything works great.  However, going all the way back to GFS1 on RHEL 5.1 (I think it was), I've had occasional locking problems that force a reboot of one or both cluster nodes.  Lately I've paid closer attention since it's been happening more often.

I'll notice the problem when the load average starts rising.  It's always tied to "stuck" processes, and I believe always tied to IMAP clients (I'm running Dovecot.)  It seems like a file belonging to user "x" (in this case, "jforrest" will become locked in some way, such that every IMAP process tied that user will get stuck on the same thing.  Over time, as the user keeps trying to read that file, more & more processes accumulate.  They're always in state "D" (uninterruptible sleep), and always on "dlm_posix_lock" according to WCHAN.  The only way I'm able to get out of this state is to reboot.  If I let it persist for too long, I/O generally stops entirely.

This certainly seems like it ought to have a definite solution, but I've no idea what it is.  I've tried a variety of things using "find" to pinpoint a particular file, but everything belonging to the affected user seems just fine.  At least, I can read and copy all of the files, and do a stat via ls -l.

Is it possible that this is a bug, not within GFS at all, but within Dovecot IMAP?

Any thoughts would be appreciated.  It's been getting worse lately and thus no fun at all.

Cheers,
Allen

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