Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755646AbYGJKaw (ORCPT ); Thu, 10 Jul 2008 06:30:52 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752699AbYGJKao (ORCPT ); Thu, 10 Jul 2008 06:30:44 -0400 Received: from mail164.messagelabs.com ([216.82.253.131]:12512 "EHLO mail164.messagelabs.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752419AbYGJKao (ORCPT ); Thu, 10 Jul 2008 06:30:44 -0400 X-VirusChecked: Checked X-Env-Sender: Uwe.Kleine-Koenig@digi.com X-Msg-Ref: server-11.tower-164.messagelabs.com!1215685843!26828935!1 X-StarScan-Version: 5.5.12.14.2; banners=-,-,- X-Originating-IP: [66.77.174.13] Date: Thu, 10 Jul 2008 12:30:36 +0200 From: Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= To: Alan Cox CC: Magnus Damm , "linux-kernel@vger.kernel.org" , "gregkh@suse.de" , "akpm@linux-foundation.org" , "hjk@linutronix.de" , "lethal@linux-sh.org" , "tglx@linutronix.de" Subject: Re: [PATCH] uio: uio_pdrv_genirq V2 Message-ID: <20080710103036.GA32507@digi.com> References: <20080710035254.27378.18682.sendpatchset@rx1.opensource.se> <20080710065639.GA16794@digi.com> <20080710094641.0c52eaa7@the-village.bc.nu> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20080710094641.0c52eaa7@the-village.bc.nu> User-Agent: Mutt/1.5.13 (2006-08-11) X-OriginalArrivalTime: 10 Jul 2008 10:30:40.0065 (UTC) FILETIME=[FFCCB310:01C8E277] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1484 Lines: 37 Alan Cox wrote: > > > > + else if (!irq_on && !priv->irq_disabled) > > > + disable_irq(dev_info->irq); > > I'm not sure if this is a problem on SMP. Should you use > > disable_irq_nosync here, too? Probably it's OK. > > That one will also deadlock. Can you explain why? I think irqcontrol is only called in task context. I only see one possible deadlock and that's disable_irq being called while the irq is IRQ_INPROGRESS on the same cpu. I'm always willing to learn. > The easiest fix is probably to use test_and_set and friends for each I/O > operation. Actually using spinlock + irq_disabled variable is new in V2 of this patch. Don't know why this changed, though. > You would then not need the lock to protect ->irq_disabled. > Propogating that throughout means your user space has to handle the case > of an IRQ arriving after disable returns but would be a fair bit saner I > think ? I think I didn't understand you right here, with the lock this can happen, too, doesn't it? Best regards Uwe -- Uwe Kleine-K?nig, Software Engineer Digi International GmbH Branch Breisach, K?ferstrasse 8, 79206 Breisach, Germany Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962 -- 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/