From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [RFC] libata new EH document Date: Thu, 01 Sep 2005 09:24:57 -0400 Message-ID: <1125581097.4834.5.camel@mulgrave> References: <20050901043850.15186.qmail@web51611.mail.yahoo.com> <43169520.6040008@gmail.com> <20050901055421.GA23496@havoc.gtf.org> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat16.steeleye.com ([209.192.50.48]:54967 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S965101AbVIANdr (ORCPT ); Thu, 1 Sep 2005 09:33:47 -0400 In-Reply-To: <20050901055421.GA23496@havoc.gtf.org> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: Jeff Garzik Cc: Tejun Heo , ltuikov@yahoo.com, Luben Tuikov , Albert Lee , linux-ide@vger.kernel.org, SCSI Mailing List , Doug Maxey On Thu, 2005-09-01 at 01:54 -0400, Jeff Garzik wrote: > The long term direction for the SCSI core seems to be that of > requiring auto-sensing. No, I don't see the mid-layer error thread handling of this ever going away. > libata is simply being lazy: while the SCSI core continues to support > kicking the EH thread when sense is missing, it's preferred for libata > to reuse that infrastructure. That makes the most sense ;-) > Auto-sensing (and READ LOG EXT for NCQ errors) requires either an > FSM or a kernel thread, to initiate a secondary qc for REQUEST SENSE. > Since the common infrastructure already exists for this, libata reuses > the existing SCSI EH kernel thread. The current SCSI autosense in drivers doesn't require this because we reuse the existing command that got the contingent allegiance condition. This is the piece I'd like to get rid of because the extra fields and extra setup to allow the command to be reused are a critical path hit. If you look at any driver that does this (53c700.c for instance) you'll see that the command is turned around and resubmitted in the irq routine). James