From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S932129Ab0IXNlV (ORCPT <rfc822;w@1wt.eu>);
	Fri, 24 Sep 2010 09:41:21 -0400
Received: from e2.ny.us.ibm.com ([32.97.182.142]:34958 "EHLO e2.ny.us.ibm.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S932075Ab0IXNlT (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 24 Sep 2010 09:41:19 -0400
Message-ID: <4C9CAA80.1030702@linux.vnet.ibm.com>
Date: Fri, 24 Sep 2010 08:41:20 -0500
From: Brian King <brking@linux.vnet.ibm.com>
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.11) Gecko/20100714 SUSE/3.0.6 Thunderbird/3.0.6
MIME-Version: 1.0
To: "Nicholas A. Bellinger" <nab@linux-iscsi.org>
CC: linux-scsi <linux-scsi@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Vasu Dev <vasu.dev@linux.intel.com>,
        Tim Chen <tim.c.chen@linux.intel.com>, Andi Kleen <ak@linux.intel.com>,
        Matthew Wilcox <willy@linux.intel.com>,
        James Bottomley <James.Bottomley@suse.de>,
        Mike Christie <michaelc@cs.wisc.edu>,
        James Smart <james.smart@emulex.com>,
        Andrew Vasquez <andrew.vasquez@qlogic.com>,
        FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>,
        Hannes Reinecke <hare@suse.de>, Joe Eykholt <jeykholt@cisco.com>,
        Christoph Hellwig <hch@lst.de>,
        MPTFusionLinux <DL-MPTFusionLinux@lsi.com>,
        "eata.c maintainer" <dario.ballabio@inwind.it>
Subject: Re: [RFC v3 01/15] scsi: Drop struct Scsi_Host->host_lock usage in
 scsi_dispatch_cmd()
References: <1285285052-16351-1-git-send-email-nab@linux-iscsi.org>
In-Reply-To: <1285285052-16351-1-git-send-email-nab@linux-iscsi.org>
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 09/23/2010 06:37 PM, Nicholas A. Bellinger wrote:
> @@ -651,7 +655,6 @@ static inline void scsi_cmd_get_serial(struct Scsi_Host *host, struct scsi_cmnd
>  int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
>  {
>  	struct Scsi_Host *host = cmd->device->host;
> -	unsigned long flags = 0;
>  	unsigned long timeout;
>  	int rtn = 0;
> 
> @@ -736,15 +739,11 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
>  		scsi_done(cmd);
>  		goto out;
>  	}
> -
> -	spin_lock_irqsave(host->host_lock, flags);
>  	/*
> -	 * AK: unlikely race here: for some reason the timer could
> -	 * expire before the serial number is set up below.
> -	 *
> -	 * TODO: kill serial or move to blk layer
> +	 * Note that scsi_cmd_get_serial() used to be called here, but
> +	 * now we expect the legacy SCSI LLDs that actually need this
> +	 * to call it directly within their SHT->queuecommand() caller.
>  	 */
> -	scsi_cmd_get_serial(host, cmd); 
> 
>  	if (unlikely(host->shost_state == SHOST_DEL)) {
>  		cmd->result = (DID_NO_CONNECT << 16);
> @@ -753,7 +752,7 @@ int scsi_dispatch_cmd(struct scsi_cmnd *cmd)
>  		trace_scsi_dispatch_cmd_start(cmd);
>  		rtn = host->hostt->queuecommand(cmd, scsi_done);
>  	}
> -	spin_unlock_irqrestore(host->host_lock, flags);
> +
>  	if (rtn) {
>  		trace_scsi_dispatch_cmd_error(cmd, rtn);
>  		if (rtn != SCSI_MLQUEUE_DEVICE_BUSY &&

Are you planning a future revision that moves the acquiring of the host lock
into the LLDD's queuecommand for all the other drivers you don't currently
touch in this patch set?

-- 
Brian King
Linux on Power Virtualization
IBM Linux Technology Center