From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755576Ab0IQDGn (ORCPT ); Thu, 16 Sep 2010 23:06:43 -0400 Received: from smtp104.sbc.mail.gq1.yahoo.com ([67.195.15.63]:48948 "HELO smtp104.sbc.mail.gq1.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753776Ab0IQDGl (ORCPT ); Thu, 16 Sep 2010 23:06:41 -0400 X-Yahoo-SMTP: fzDSGlOswBCWnIOrNw7KwwK1j9PqyNbe5PtLKiS4dDU.UNl_t6bdEZu9tTLW X-YMail-OSG: t9_X6sAVM1lgmdxz8rEZq3PtkPUtaqzVGce2Xk6HFWHrSOn .YSQf3kzGuVK0EssP7eDefC00SbI1eWmpbTr51oHMhc7qeJV5P1UbYLZD4p. bR9QXHFp.qxpGnlT6UxUT8sbCj9EDVMvEcFZEKJdOl019.tFaai957uX3Ns1 XQlgL.mlFqwd62t1Z9_7J1W8B8e27JDVgpRO1Nu7QPjdjPQ91QNZ.qDEjl4Y K9QOwSp3haNL4f3Cbpp5.N8yMhQSwIz0neOMOjI7YLRXZeWABbwNkMcOvZOV pO6F6rJKKC.AiFyWZc_NGyfWpYrOzX5_I54XeuJIHJSWxSMqUusZ2O_FFYEZ N_E2nGXNFQcYFj9pRhg-- X-Yahoo-Newman-Property: ymail-3 Subject: Re: [PATCH 1/8] scsi: Drop struct Scsi_Host->host_lock around SHT->queuecommand() From: "Nicholas A. Bellinger" To: James Bottomley Cc: linux-scsi , linux-kernel , Vasu Dev , Tim Chen , Andi Kleen , Matthew Wilcox , Mike Christie , James Smart , Andrew Vasquez , FUJITA Tomonori , Hannes Reinecke , Joe Eykholt , Christoph Hellwig In-Reply-To: <1284691571.26423.50.camel@mulgrave.site> References: <1284676529-10756-1-git-send-email-nab@linux-iscsi.org> <1284691571.26423.50.camel@mulgrave.site> Content-Type: text/plain Date: Thu, 16 Sep 2010 20:02:32 -0700 Message-Id: <1284692552.13344.143.camel@haakon2.linux-iscsi.org> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2010-09-16 at 22:46 -0400, James Bottomley wrote: > On Thu, 2010-09-16 at 15:35 -0700, Nicholas A. Bellinger wrote: > > From: Nicholas Bellinger > > > > This patch converts scsi_dispatch_cmd() to only hold struct Scsi_Host->host_lock > > for scsi_cmd_get_serial(), and drops the lock because the call into > > the LLD with host->hostt->queuecommand(). > > > > Signed-off-by: Nicholas A. Bellinger > > --- > > drivers/scsi/scsi.c | 3 ++- > > 1 files changed, 2 insertions(+), 1 deletions(-) > > > > diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c > > index ad0ed21..06e5b3a 100644 > > --- a/drivers/scsi/scsi.c > > +++ b/drivers/scsi/scsi.c > > @@ -745,6 +745,7 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd) > > * TODO: kill serial or move to blk layer > > */ > > scsi_cmd_get_serial(host, cmd); > > + spin_unlock_irqrestore(host->host_lock, flags); > > So at least from where I stand, my object is to reduce the number of > times we take and release the lock, which this doesn't do. As I said > before: we need to figure out the rest, which likely includes an atomic > for the serial number (which is almost unused). I think the check > against SHOST_DEL is fine unlocked. > Ok, this makes sense if the shost_state == SHOST_DEL check really is OK to be done w/o host_lock held (I really don't know on this one..) So if that is the case, then Tim and Vasu can you guys have a look at dropping the host_lock around serial number usage and post this for review..? I will plan to include the host_lock'less serial number patch into lio-core-2.6.git/drop-host_lock with the rest of the LLD driver conversion patches from this afternoon and respin a new branch for James and Co. to review. Thanks! --nab