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Date: Fri, 17 Sep 2010 09:20:22 +0200
From: Andi Kleen <ak@linux.intel.com>
To: James Bottomley <James.Bottomley@suse.de>
Cc: "Nicholas A. Bellinger" <nab@linux-iscsi.org>,
        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>,
        Matthew Wilcox <willy@linux.intel.com>,
        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>
Subject: Re: [PATCH 1/8] scsi: Drop struct Scsi_Host->host_lock around
	SHT->queuecommand()
Message-ID: <20100917072022.GB2644@gargoyle.ger.corp.intel.com>
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> 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

If it's unused it should be removed, make optional.
Atomics are a scalability problem too and not much cheaper than spinlocks.

-Andi