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Date: Tue, 3 Jan 2012 14:35:05 -0800
From: Tejun Heo <tj@kernel.org>
To: Jens Axboe <axboe@kernel.dk>
Cc: Hugh Dickins <hughd@google.com>, Shaohua Li <shaohua.li@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
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        linux-ide@vger.kernel.org, x86@kernel.org
Subject: Re: [PATCH block/for-3.3/core] block: an exiting task should be
 allowed to create io_context
Message-ID: <20120103223505.GI31746@google.com>
References: <alpine.LSU.2.00.1112280010550.1398@eggly.anvils>
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On Tue, Jan 03, 2012 at 02:13:01PM -0800, Tejun Heo wrote:
> > That's pretty odd. Given Hughs report as well, it sure does sound like
> > we now have some life time issues with cfqq's.
> 
> Hmmm... I disabled cfqq merge logic (commented out
> cfq_close_cooperator() and the following cfq_setup_merge() calls) in
> cfq_select_queue() and neither is triggering for quite a while now.
> Maybe cfqq refcnt is getting borked over cfqq merging / splitting?  It
> would also explain the low frequency of the issue too.  I'll try to
> further isolate it but It would be awesome if someone more familiar
> with the logic can go over that part.

Scrap that.  It triggered and yeah cfq_get_next_queue() is retrieving
empty cfqq from the service tree.

Thanks.

-- 
tejun