From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754881Ab1H2TSS (ORCPT ); Mon, 29 Aug 2011 15:18:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1168 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754325Ab1H2TSQ (ORCPT ); Mon, 29 Aug 2011 15:18:16 -0400 Date: Mon, 29 Aug 2011 22:18:58 +0300 From: "Michael S. Tsirkin" To: Jan Kiszka Cc: Jesse Barnes , Brian King , "James E.J. Bottomley" , "Hans J. Koch" , Greg Kroah-Hartman , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org, kvm@vger.kernel.org Subject: Re: Broken pci_block_user_cfg_access interface Message-ID: <20110829191858.GA9415@redhat.com> References: <20110829150552.GA6851@redhat.com> <4E5BB358.3060705@siemens.com> <4E5BDEAB.5000405@siemens.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E5BDEAB.5000405@siemens.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 29, 2011 at 08:47:07PM +0200, Jan Kiszka wrote: > On 2011-08-29 17:42, Jan Kiszka wrote: > > I still don't get what prevents converting ipr to allow plain mutex > > synchronization. My vision is: > > - push reset-on-error of ipr into workqueue (or threaded IRQ?) > > I'm starting to like your proposal: I had a look at ipr, but it turned > out to be anything but trivial to convert that driver. It runs its > complete state machine under spin_lock_irq, and the functions calling > pci_block/unblock_user_cfg_access are deep inside this thing. I have no > hardware to test whatever change, and I feel a bit uncomfortable asking > Brian to redesign his driver that massively. > > So back to your idea: I would generalize pci_block_user_cfg_access to > pci_block_cfg_access. It should fail when some other site already holds > the access lock, but it should remain non-blocking - for the sake of ipr. It would be easy to have blocking and non-blocking variants. But - I have no idea whether supporting sysfs config/reset access while ipr is active makes any sense - I know we need it for uio. - reset while uio handles interrupt needs to block, not fail I think > We should still provide generic pci-2.3 IRQ masking services, but that > could be done in a second step. I could have a look at this. > > Jan > > -- > Siemens AG, Corporate Technology, CT T DE IT 1 > Corporate Competence Center Embedded Linux