From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: Prevent busy looping Date: Wed, 11 Jun 2008 17:03:32 +0900 Message-ID: <484F86D4.8050907@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from rv-out-0506.google.com ([209.85.198.227]:48279 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753748AbYFKIDk (ORCPT ); Wed, 11 Jun 2008 04:03:40 -0400 Received: by rv-out-0506.google.com with SMTP id k40so1325180rvb.1 for ; Wed, 11 Jun 2008 01:03:39 -0700 (PDT) In-Reply-To: <20080611080502.4aa43980@core> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Alan Cox Cc: James Bottomley , Jens Axboe , linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org Alan Cox wrote: >> Elias's synthetic test case triggered infinite loop because it wasn't >> a proper ->qc_defer(). ->qc_defer() should never defer commands when >> the target is idle. > > Target or host ? We *do* defer commands in the case of an idle channel > when dealing with certain simplex controllers that can only issue one > command per host not one per cable (and in fact in the general case we > can defer commands due to activity on the other drive on the cable). The term was confusing. I used target to mean both device (ATA_DEFER_LINK) and host (ATA_DEFER_PORT). Hmmm... in simplex case, yeah, blocked counters need to be > 1. We'll need to increase blocked counts after all. I'll test blocked counts of 2 w/ PMP and make sure it doesn't incur unnecessary delays and post the patch. Thanks. -- tejun