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=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 37F8AC433DB for ; Wed, 10 Feb 2021 22:21:38 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CE37464DD8 for ; Wed, 10 Feb 2021 22:21:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE37464DD8 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:41532 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l9xrc-0006o0-Pg for qemu-devel@archiver.kernel.org; Wed, 10 Feb 2021 17:21:36 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:57762) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1l9xmN-000218-1s for qemu-devel@nongnu.org; Wed, 10 Feb 2021 17:16:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:55411) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1l9xmD-0005BK-5z for qemu-devel@nongnu.org; Wed, 10 Feb 2021 17:16:10 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1612995359; 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=HEH6FvmbJgbpMEy5AX6rry8qG7GqcYH7uQPYcSVJ/jQ=; b=e5LQbMG6TyMgFKhVNTWQE5XCKxuNMdI8L5hJSA/4JuHP/2bIoS2SeHOCWvm/LFqSltf9oH ALTLb9U7fLVKH4QKtfvgUvzRIoX20yowFominCUcvlj8GYe2K5rSRfQH01C6z9wnxwFU/g xo7+vDsx7fwC0k7jj/ifR6d2b5fky/8= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-50-gHJpyYYcNLePncblwf66uQ-1; Wed, 10 Feb 2021 17:15:58 -0500 X-MC-Unique: gHJpyYYcNLePncblwf66uQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 29C1D107ACE3 for ; Wed, 10 Feb 2021 22:15:57 +0000 (UTC) Received: from horse.redhat.com (ovpn-113-163.rdu2.redhat.com [10.10.113.163]) by smtp.corp.redhat.com (Postfix) with ESMTP id 195CA7092D; Wed, 10 Feb 2021 22:15:45 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id A299F220BCF; Wed, 10 Feb 2021 17:15:44 -0500 (EST) Date: Wed, 10 Feb 2021 17:15:44 -0500 From: Vivek Goyal To: "Michael S. Tsirkin" Subject: Re: [RFC PATCH 0/6] vhost-user: Shutdown/Flush slave channel properly Message-ID: <20210210221544.GC3200@redhat.com> References: <20210125180115.22936-1-vgoyal@redhat.com> <20210210163830-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: <20210210163830-mutt-send-email-mst@kernel.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=vgoyal@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=vgoyal@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -33 X-Spam_score: -3.4 X-Spam_bar: --- X-Spam_report: (-3.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: virtio-fs@redhat.com, marcandre.lureau@redhat.com, qemu-devel@nongnu.org, stefanha@redhat.com, dgilbert@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Feb 10, 2021 at 04:39:06PM -0500, Michael S. Tsirkin wrote: > On Mon, Jan 25, 2021 at 01:01:09PM -0500, Vivek Goyal wrote: > > Hi, > > > > We are working on DAX support in virtiofs and have some patches out of > > the tree hosted here. > > > > https://gitlab.com/virtio-fs/qemu/-/commits/virtio-fs-dev > > > > These patches have not been proposed for merge yet, becasue David > > Gilbert noticed that we can run into a deadlock during an emergency > > reboot of guest kernel. (echo b > /proc/sysrq-trigger). > > > > I have provided details of deadlock in 4th path of the series with > > subject "qemu, vhost-user: Extend protocol to start/stop/flush slave > > channel". > > > > Basic problem seems to be that we don't have a proper mechanism to > > shutdown slave channel when vhost-user device is stopping. This means > > there might be pending messages in slave channel and slave is blocked > > and waiting for response. > > > > This is an RFC patch series to enhance vhost-user protocol to > > properly shutdown/flush slave channel and avoid the deadlock. Though > > we faced the issue in the context of virtiofs, any vhost-user > > device using slave channel can potentially run into issues and > > can benefit from these patches. > > > > Any feedback is welcome. Currently patches are based on out of > > tree code but after I get some feedback, I can only take pieces > > which are relevant to upstream and post separately. > > > > Thanks > > Vivek > > No comments so far - do you plan to post a non-RFC patchset? Yes. Stefan wants me to poll both unix fd and slave fd in device shutdown path and serve both of these in parallel, instead of adding a new slave channel shutdown message. I am planning to give it a try and post new patches. Vivek > > > > Vivek Goyal (6): > > virtiofsd: Drop ->vu_dispatch_rwlock while waiting for thread to exit > > libvhost-user: Use slave_mutex in all slave messages > > vhost-user: Return error code from slave_read() > > qemu, vhost-user: Extend protocol to start/stop/flush slave channel > > libvhost-user: Add support to start/stop/flush slave channel > > virtiofsd: Opt in for slave start/stop/shutdown functionality > > > > hw/virtio/vhost-user.c | 151 +++++++++++++++++++++- > > subprojects/libvhost-user/libvhost-user.c | 147 +++++++++++++++++---- > > subprojects/libvhost-user/libvhost-user.h | 8 +- > > tools/virtiofsd/fuse_virtio.c | 20 +++ > > 4 files changed, 294 insertions(+), 32 deletions(-) > > > > -- > > 2.25.4 >