From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Prevent busy looping Date: Thu, 12 Jun 2008 22:43:29 +0900 Message-ID: <48512801.7090502@gmail.com> References: <20080416151305.8788.63912.stgit@denkblock.local> <20080416163152.GK12774@kernel.dk> <87r6d5l9pb.fsf@denkblock.local> <20080417071335.GR12774@kernel.dk> <87ve2gc1bn.fsf@denkblock.local> <484F7A8D.1040809@gmail.com> <20080611080502.4aa43980@core> <484F86D4.8050907@gmail.com> <485092C9.3050309@gmail.com> <87d4mmubvf.fsf@denkblock.local> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <87d4mmubvf.fsf@denkblock.local> Sender: linux-scsi-owner@vger.kernel.org To: Elias Oltmanns Cc: Alan Cox , James Bottomley , Jens Axboe , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-ide@vger.kernel.org Elias Oltmanns wrote: > Since I'm a little confused by your comment, please explain again. Do > you mean to say that busy looping doesn't lock up the machine in general > or merely in the case of a simplex configuration? It busy loops but it won't lock up as command completion is the loop breaker and command completion comes via IRQ and the busy looping doesn't happen solely in the IRQ context. Still needs to be fixed tho. Anyways, this is only limited to ->qc_defer for simplex and the reason why there's busy loop is because we're trying to schedule two independent hosts and SCSI midlayer (of course) doesn't have the notion of cross host deferring. Thanks. -- tejun