https://bugzilla.novell.com/show_bug.cgi?id=881912
https://bugzilla.novell.com/show_bug.cgi?id=881912#c2
Neil Brown changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |RESOLVED
CC| |nfbrown@suse.com
Resolution| |FIXED
AssignedTo|kernel-maintainers@forge.pr |nfbrown@suse.com
|ovo.novell.com |
--- Comment #2 from Neil Brown 2014-06-10 02:13:55 UTC ---
1/ I strongly recommend against "soft" mounts. They are a bad idea and should
never be used. They can easily lead to data loss.
2/ The soft lockups shown in the log are caused by NFSv4.
When a file is accessed via NFSv4 the server will often hand out a
"delegation" for that file, so the client can keep it cached without further
reference to the server (without a delegation it would need to check
periodically that no-one else has changed the file).
When imapd calls utime() to set the timestamps on the file, the delegation
needs to be recalled. So the server has to call the client and tell it that
the lease is recalled, and has to wait for the client to reply.
It should sleep while it is waiting which would not cause a "soft lockup".
However due to a bug it doesn't, so it spins instead. After spinning for about
20 seconds we get the soft-lockup message.
This bug was fixed upstream by
commit f1c6bb2cb8b81013e8979806f8e15e3d53efb96d
Author: Jeff Layton
Date: Tue Apr 15 06:17:49 2014 -0400
locks: allow __break_lease to sleep even when break_time is 0
which was backported to v3.14.4.
I don't think there is anything I can do to expedite this fix into Tumbleweed.
The next kernel release there is sure to include the fix. In fact, I think
3.14.4 is already in Tumbleweed:
http://download.opensuse.org/repositories/openSUSE:/Tumbleweed/standard/i686...
The bug does not exist in the openSUSE-13.1 kernel.
Even without the soft lockup you could get delays due to recalling the
delegation. A very recent change to the kernel (not in mainline yet) causes
the server not to hand out delegations so often. That might help a bit, or it
might not.
But there must be some file that is being accessed by imapd and via NFS. You
could possibly run 'strace' on imapd and look for utimes calls that take longer
than you might expect (it could often take less than 20 seconds and only
occasionally cause a soft lockup) ... or look for any utimes calls and try to
see if there are any file which might be accessed remotely.
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