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Date: Wed, 03 Mar 2010 13:37:25 +0100
From: John Hughes <john@Calva.COM>
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To: Jens Axboe <jens.axboe@oracle.com>
CC: Andrew Morton <akpm@linux-foundation.org>,
       bugzilla-daemon@bugzilla.kernel.org, bugme-daemon@bugzilla.kernel.org,
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Subject: Re: [Bugme-new] [Bug 15426] New: Running many copies of bonnie++
 on different filesystems seems to deadlock in sync
References: <bug-15426-10286@http.bugzilla.kernel.org/> <20100302161627.bf02d0a2.akpm@linux-foundation.org> <4B8E517E.3010702@Calva.COM> <20100303115015.GN5768@kernel.dk>
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Jens Axboe wrote:
> Is IO still going on, or does it appear to be stuck? From the traces
> below, we have various procs caught in waiting for a request. So if
> things are totally stuck, it could be some race in there.
>   
I see I/O happening on three or four of the disks.

Just a thought.  What exactly is sync(2) supposed to do - block until 
there are no more dirty pages, or block until all pages that were dirty 
when the sync was done are clean?  In other words is the problem simply 
that pages are being dirtied faster than the sync is writing them out?