Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965034AbWEBXTP (ORCPT ); Tue, 2 May 2006 19:19:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965036AbWEBXTP (ORCPT ); Tue, 2 May 2006 19:19:15 -0400 Received: from smtpout.mac.com ([17.250.248.176]:3833 "EHLO smtpout.mac.com") by vger.kernel.org with ESMTP id S965034AbWEBXTP (ORCPT ); Tue, 2 May 2006 19:19:15 -0400 In-Reply-To: <20060502214908.GB18192@vrfy.org> References: <20060428112225.418cadd9.holzheu@de.ibm.com> <20060429075311.GB1886@kroah.com> <8A7D2F4D-5A05-4C93-B514-03268CAA9201@mac.com> <20060429215501.GA9870@kroah.com> <4237705F-E1B2-46CF-BE66-EFB77F68EC42@mac.com> <20060501203815.GE19423@kroah.com> <2DBA690E-B11A-478E-B2E0-0529F4CE45A9@mac.com> <20060502040053.GA14413@kroah.com> <13D6E299-061B-46A5-A3CD-12E1075B9451@mac.com> <20060502213043.GB30957@kroah.com> <20060502214908.GB18192@vrfy.org> Mime-Version: 1.0 (Apple Message framework v746.3) Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed Message-Id: Cc: Greg KH , Michael Holzheu , akpm@osdl.org, schwidefsky@de.ibm.com, penberg@cs.helsinki.fi, ioe-lkml@rameria.de, joern@wohnheim.fh-wedel.de, linux-kernel@vger.kernel.org Content-Transfer-Encoding: 7bit From: Kyle Moffett Subject: Re: [PATCH] s390: Hypervisor File System Date: Tue, 2 May 2006 19:18:52 -0400 To: Kay Sievers X-Mailer: Apple Mail (2.746.3) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1357 Lines: 37 On May 2, 2006, at 17:49:08, Kay Sievers wrote: > If you can assume that processes accessing the values are > cooperative, it already works without any changes: > > $ time flock /sys/class/firmware echo 1 > /sys/class/firmware/ > timeout > real 0m0.005s > > $ flock /sys/class/firmware sleep 5& > [1] 6468 > > $ time flock /sys/class/firmware echo 1 > /sys/class/firmware/ > timeout > real 0m3.558s But that doesn't solve the problem for framebuffer devices or for the s390 code. Such transactions have one or more of the following properties: (1) A read operation is _expensive_ or adds unacceptable latencies and should be done as rarely as possible (2) The data must be all written to hardware simultaneously by the kernel; a partial update does not make sense and would cause undesired operation from the hardware. The idea with the transactions would be to create a kernel-memory buffer-layer of sorts on top of the underlying sysfs tree to cache the read data and collect writes for an atomic commit. I'll see if I can make something work. Cheers, Kyle Moffett - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/