Re: nfsd oops on Linus' current tree.

[Myklebust, Trond]

On Thu, 2013-01-03 at 17:08 -0500, Tejun Heo wrote:
+AD4- Hello,
+AD4- 
+AD4- On Thu, Jan 03, 2013 at 03:11:20PM -0500, J. Bruce Fields wrote:
+AD4- +AD4- Both rpciod and nfsiod already set WQ+AF8-MEM+AF8-RECLAIM.
+AD4- +AD4- 
+AD4- +AD4- But, right, looking at kernel/workqueue.c, it seems that the dedicated
+AD4- +AD4- +ACI-rescuer+ACI- threads are invoked only in the case when work is stalled
+AD4- +AD4- because a new worker thread isn't allocated quickly enough.
+AD4- 
+AD4- Because that's the +ACo-only+ACo- case where progress can't be guaranteed
+AD4- otherwise.
+AD4- 
+AD4- +AD4- So, what to do that's simplest enough that it would work for
+AD4- +AD4- post-rc2/stable?  I was happy having just a simple dedicated
+AD4- +AD4- thread--these are only started when nfsd is, so there's no real thread
+AD4- +AD4- proliferation problem.
+AD4- 
+AD4- The analysis is likely completely wrong, so please don't go off doing
+AD4- something unnecessary.  Please take look at what's causing the
+AD4- deadlocks again.

The analysis is a no-brainer:
We see a deadlock due to one work item waiting for completion of another
work item that is queued on the same CPU. There is no other dependency
between the two work items.

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust+AEA-netapp.com
www.netapp.com
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