From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.5 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28C1FC433E0 for ; Mon, 8 Feb 2021 10:54:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D53ED64E7B for ; Mon, 8 Feb 2021 10:54:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232164AbhBHKyf (ORCPT ); Mon, 8 Feb 2021 05:54:35 -0500 Received: from mail.xenproject.org ([104.130.215.37]:50004 "EHLO mail.xenproject.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232539AbhBHKl5 (ORCPT ); Mon, 8 Feb 2021 05:41:57 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=xen.org; s=20200302mail; h=Content-Transfer-Encoding:Content-Type:In-Reply-To: MIME-Version:Date:Message-ID:From:References:Cc:To:Subject; bh=IQPlMuHphzCxemau7EPG8KdIBVritDvW1xuyCMc3fhU=; b=sC+AR9iTEqeFWbDuKWB5Y35WRU 0RbDCYD8HqDZ5+YavvWLxIKZjjBgShWRRynceb425BC8VjwpIVUA9HMJAGLCISgOYcuyi1zxNzhqU swR71F4tJ9r/e/ArJUxgAMKjDK+qn++/QfBSK2/QATA/oMqTo/0taQ58egBGhScfddCo=; Received: from xenbits.xenproject.org ([104.239.192.120]) by mail.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1l93yJ-0001Vr-NE; Mon, 08 Feb 2021 10:40:47 +0000 Received: from [54.239.6.177] (helo=a483e7b01a66.ant.amazon.com) by xenbits.xenproject.org with esmtpsa (TLS1.3:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.92) (envelope-from ) id 1l93yJ-0004LV-Ej; Mon, 08 Feb 2021 10:40:47 +0000 Subject: Re: [PATCH 0/7] xen/events: bug fixes and some diagnostic aids To: =?UTF-8?B?SsO8cmdlbiBHcm/Dnw==?= , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, netdev@vger.kernel.org, linux-scsi@vger.kernel.org Cc: Boris Ostrovsky , Stefano Stabellini , stable@vger.kernel.org, Konrad Rzeszutek Wilk , =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= , Jens Axboe , Wei Liu , Paul Durrant , "David S. Miller" , Jakub Kicinski References: <20210206104932.29064-1-jgross@suse.com> <7aaeeb3d-1e1b-6166-84e9-481153811b62@suse.com> <6f547bb5-777a-6fc2-eba2-cccb4adfca87@xen.org> <0d623c98-a714-1639-cc53-f58ba3f08212@suse.com> From: Julien Grall Message-ID: <28399fd1-9fe8-f31a-6ee8-e78de567155b@xen.org> Date: Mon, 8 Feb 2021 10:40:44 +0000 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <0d623c98-a714-1639-cc53-f58ba3f08212@suse.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Juergen, On 08/02/2021 10:22, Jürgen Groß wrote: > On 08.02.21 10:54, Julien Grall wrote: >> ... I don't really see how the difference matter here. The idea is to >> re-use what's already existing rather than trying to re-invent the >> wheel with an extra lock (or whatever we can come up). > > The difference is that the race is occurring _before_ any IRQ is > involved. So I don't see how modification of IRQ handling would help. Roughly our current IRQ handling flow (handle_eoi_irq()) looks like: if ( irq in progress ) { set IRQS_PENDING return; } do { clear IRQS_PENDING handle_irq() } while (IRQS_PENDING is set) IRQ handling flow like handle_fasteoi_irq() looks like: if ( irq in progress ) return; handle_irq() The latter flow would catch "spurious" interrupt and ignore them. So it would handle nicely the race when changing the event affinity. Cheers, -- Julien Grall