From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [PATCH block/for-3.3/core] block: an exiting task should be allowed to create io_context Date: Tue, 3 Jan 2012 14:35:05 -0800 Message-ID: <20120103223505.GI31746@google.com> References: <20111228164836.GP17712@google.com> <20111228211918.GA3516@google.com> <20120103173500.GB31746@google.com> <20120103175922.GC31746@google.com> <20120103200906.GG31746@google.com> <4F03631C.8080501@kernel.dk> <20120103221301.GH31746@google.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20120103221301.GH31746@google.com> Sender: linux-kernel-owner@vger.kernel.org To: Jens Axboe Cc: Hugh Dickins , Shaohua Li , Andrew Morton , Stephen Rothwell , linux-next@vger.kernel.org, LKML , linux-scsi@vger.kernel.org, linux-ide@vger.kernel.org, x86@kernel.org List-Id: linux-next.vger.kernel.org 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