From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Wed, 5 Feb 2003 11:47:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Wed, 5 Feb 2003 11:47:50 -0500 Received: from 216-239-45-4.google.com ([216.239.45.4]:57986 "EHLO 216-239-45-4.google.com") by vger.kernel.org with ESMTP id ; Wed, 5 Feb 2003 11:47:49 -0500 Message-ID: <3E414243.4090303@google.com> Date: Wed, 05 Feb 2003 08:56:35 -0800 From: Ross Biro User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.0.1) Gecko/20020826 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Benjamin Herrenschmidt CC: alan@redhat.com, Stephan von Krawczynski , linux-kernel@vger.kernel.org Subject: Re: 2.4.21-pre4: PDC ide driver problems with shared interrupts References: <20030202161837.010bed14.skraw@ithnet.com> <3E3D4C08.2030300@pobox.com> <20030202185205.261a45ce.skraw@ithnet.com> <3E3D6367.9090907@pobox.com> <20030205104845.17a0553c.skraw@ithnet.com> <1044443761.685.44.camel@zion.wanadoo.fr> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Benjamin Herrenschmidt wrote: >>Okay, I had to watch for it a bit longer and it turns out that the kernel PDC driver has a problem in this shared interrupt setup. When loads get high it seems to run into some timing problem which causes things like: >> >>Feb 4 01:02:22 admin kernel: hde: dma_intr: status=0xd0 { Busy } >> >> >> Since the busy bit is set, we know the drive must have received a command. Since dma_intr thought the drive was not busy, an interrupt must have snuck through between the command being issued and the dma being started. I think in my original patch, I had the dma start outside of the spinlock, that is a bug. The command to the controller to start the dma must be inside of the spinlock. I have not looked at 2.4.21-pre4 at all, so I could be entirely off base here. Ross