From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matthew Wilcox Subject: Documentation/io_ordering.txt is wrong Date: Sat, 18 Sep 2004 18:57:14 +0100 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20040918175714.GD642@parcelfarce.linux.theplanet.co.uk> References: <20040917183029.GW642@parcelfarce.linux.theplanet.co.uk> <20040918061001.GC21456@colo.lackof.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from parcelfarce.linux.theplanet.co.uk ([195.92.249.252]:38623 "EHLO www.linux.org.uk") by vger.kernel.org with ESMTP id S269130AbUIRR5Q (ORCPT ); Sat, 18 Sep 2004 13:57:16 -0400 Content-Disposition: inline In-Reply-To: <20040918061001.GC21456@colo.lackof.org> List-Id: linux-scsi@vger.kernel.org To: Grant Grundler Cc: Jesse Barnes , Andrew Vasquez , pj@sgi.com, linux-scsi@vger.kernel.org, mdr@cthulhu.engr.sgi.com, jeremy@cthulhu.engr.sgi.com, djh@cthulhu.engr.sgi.com, Andrew Morton , linux-kernel@vger.kernel.org On Sat, Sep 18, 2004 at 12:10:01AM -0600, Grant Grundler wrote: > Jesse Barnes wrote: > ... > > Btw Andrew (Vasquez), there's a small doc I put together that should describe > > when you have to worry about PCI posting. It's in the tree: > > Documentation/io_ordering.txt. If it's incomplete or confusing, just let me > > know and I'll update it. > > Jesse, > Both. incomplete and confusing. > "concrete example of a hypothetical driver" wasn't my first warning > this document needed work. :^) Not just incomplete and confusing, but actively wrong. spin_lock/ spin_unlock should imply ordering of readb(). What you're describing there is __readb(). See Documentation/DocBook/deviceiobook.tmpl. Also, rmb() should ensure ordering of io reads; there should be no need to touch the device. -- "Next the statesmen will invent cheap lies, putting the blame upon the nation that is attacked, and every man will be glad of those conscience-soothing falsities, and will diligently study them, and refuse to examine any refutations of them; and thus he will by and by convince himself that the war is just, and will thank God for the better sleep he enjoys after this process of grotesque self-deception." -- Mark Twain