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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 00350D6E2CF for ; Wed, 20 Nov 2024 08:17:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gLoIyx3MwjYje1cCzOJ5zph/jdarSH9KY05cS8kqUro=; b=yHNGRULXH1su1JqnNxUgSI+Lr9 SNagyGXxCz4dbyAgJDUuTMivEA63kdKx/mHf7jeyS6wDJN6rQDaS/HOB84Lr0WYXM7521osUtnotM /zM3/PZbVrHOhZBvcK/6QKnI8Fj+PknlYF+IHckKKjFL0vP3zgKDsf83alDp9A6x+Qvnja5DS2c/R LH5sUQ4nMY5sD1VYFoy0C5XKUEC5GVOm+JW9vZSMoHOuaJeZniAXOfi7cr/gOXBpeM6vocGT2JDhC Oh1Y0IPpRhFAlgkhG8pAVvP26AlGhiXjMTTxp6HN9Y1QJ2mG0ZtjBmW5/Wrbf7ysTjD+d2C31NCfF bEAI+EOg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98 #2 (Red Hat Linux)) id 1tDftZ-0000000EieT-2iGb; Wed, 20 Nov 2024 08:17:05 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98 #2 (Red Hat Linux)) id 1tDftW-0000000Eidi-33gX for kexec@lists.infradead.org; Wed, 20 Nov 2024 08:17:04 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1732090621; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=gLoIyx3MwjYje1cCzOJ5zph/jdarSH9KY05cS8kqUro=; b=YcqAYNOG81H1DcDRMtZMLyD2U75DQ9FwVrBEg9/LaplUh8B0jV3m1rdlejw35CvyMQfB0E erpvfkGAAHe1jjq17BqjHUeHwXGk7eCr4D3rgiIF8I9FGnDwkhWL8/QBIThWbw23ROnoEl Vls/U4VI66YnnmLasF0of9HeDBZgydA= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-628-xwZYZB6JPMep3tIsEwHwCg-1; Wed, 20 Nov 2024 03:16:58 -0500 X-MC-Unique: xwZYZB6JPMep3tIsEwHwCg-1 X-Mimecast-MFC-AGG-ID: xwZYZB6JPMep3tIsEwHwCg Received: from mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.15]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 5768E19560A1; Wed, 20 Nov 2024 08:16:55 +0000 (UTC) Received: from localhost (unknown [10.72.113.10]) by mx-prod-int-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 790CA1955F43; Wed, 20 Nov 2024 08:16:53 +0000 (UTC) Date: Wed, 20 Nov 2024 16:16:38 +0800 From: Baoquan He To: David Hildenbrand Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-s390@vger.kernel.org, virtualization@lists.linux.dev, kvm@vger.kernel.org, linux-fsdevel@vger.kernel.org, kexec@lists.infradead.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Vivek Goyal , Dave Young , Thomas Huth , Cornelia Huck , Janosch Frank , Claudio Imbrenda , Eric Farman , Andrew Morton Subject: Re: [PATCH v1 01/11] fs/proc/vmcore: convert vmcore_cb_lock into vmcore_mutex Message-ID: References: <20241025151134.1275575-1-david@redhat.com> <20241025151134.1275575-2-david@redhat.com> <2b5c2b71-d31b-406d-abc5-d9a0a67712f5@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2b5c2b71-d31b-406d-abc5-d9a0a67712f5@redhat.com> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.15 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241120_001702_835308_0B545710 X-CRM114-Status: GOOD ( 21.28 ) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 11/15/24 at 11:03am, David Hildenbrand wrote: > On 15.11.24 10:30, Baoquan He wrote: > > On 10/25/24 at 05:11pm, David Hildenbrand wrote: > > > We want to protect vmcore modifications from concurrent opening of > > > the vmcore, and also serialize vmcore modiciations. Let's convert the > > > > > > > spinlock into a mutex, because some of the operations we'll be > > > protecting might sleep (e.g., memory allocations) and might take a bit > > > longer. > > > > Could you elaborate this a little further. E.g the concurrent opening of > > vmcore is spot before this patchset or have been seen, and in which place > > the memory allocation is spot. Asking this becasue I'd like to learn and > > make clear if this is a existing issue and need be back ported into our > > old RHEL distros. Thanks in advance. > > It's a preparation for the other patches, that do what is described here: > > a) We can currently modify the vmcore after it was opened. This can happen > if the vmcoredd is added after the vmcore was loaded. Similar things will > happen with the PROC_VMCORE_DEVICE_RAM extension. > > b) To handle it cleanly we need to protect the modifications against > concurrent opening. And the modifcations end up allocating memory and cannot > easily take the spinlock. > > So far a spinlock was sufficient, now a mutex is required. I see, as we talked in patch 2 sub-thread, these information are very valuable to help people get the background information when they read code. Let's put it in patch log. Thanks. > > Maybe we'd want to backport 1,2,3, but not sure if we consider this critical > enough. > > -- > Cheers, > > David / dhildenb >