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Re: Hung in D state during fclose

To: "Cheung, Norman" <Norman.Cheung@xxxxxxxxxxxxxx>
Subject: Re: Hung in D state during fclose
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Wed, 13 Feb 2013 16:15:52 +1100
Cc: "'linux-xfs@xxxxxxxxxxx'" <linux-xfs@xxxxxxxxxxx>
Delivered-to: linux-xfs@xxxxxxxxxxx
In-reply-to: <3542214BE3A3EF419F236DFE0F878BC9051A09@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
References: <loom.20130212T071115-446@xxxxxxxxxxxxxx> <20130212065545.GC10731@dastard> <3542214BE3A3EF419F236DFE0F878BC90512DC@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20130212102014.GA26694@dastard> <3542214BE3A3EF419F236DFE0F878BC90517D2@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <20130212202246.GB26694@dastard> <3542214BE3A3EF419F236DFE0F878BC905190D@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> <3542214BE3A3EF419F236DFE0F878BC9051A09@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Wed, Feb 13, 2013 at 12:12:47AM +0000, Cheung, Norman wrote:
> Dave,
> 
> One other point I have forgotten to mention is that the parent
> thread will wait for 5 minutes and then lower the thread priority
> (from -2 back to 20) and set a global variable to signal the
> threads to exit.  The blocked thread responded well and exit from
> D state and fclose completed with no error.

So it's not hung - it's just very slow?

You have 256GB of memory. It's entirely possible that you've dirtied
a large amount of memory and everything is simply stuck waiting for
writeback to occur. Perhaps you should have a look at the
utilisation of your disks when this still occurs. 'iostat -x -d -m
5' will give you some insight into utilsation when a hang occurs...

> This cause me to wonder if it  is possible that  some XFS threads
> and my application thread might be in a deadlock.  

Deadlocks are permanent, so what you are seeing is not a deadlock....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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