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=-5.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 1BBBCC33C8C for ; Tue, 7 Jan 2020 13:37:22 +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 DAE852080A for ; Tue, 7 Jan 2020 13:37:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="gzdhkY5W" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DAE852080A 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]:48826 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iop2t-0006AP-UR for qemu-devel@archiver.kernel.org; Tue, 07 Jan 2020 08:37:20 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:49054) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ionZN-0003Zv-20 for qemu-devel@nongnu.org; Tue, 07 Jan 2020 07:02:50 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ionZL-00046s-Mp for qemu-devel@nongnu.org; Tue, 07 Jan 2020 07:02:44 -0500 Received: from us-smtp-2.mimecast.com ([207.211.31.81]:47000 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1ionZL-00046c-It for qemu-devel@nongnu.org; Tue, 07 Jan 2020 07:02:43 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1578398562; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=5Qj4QJXSmnXomYqyXEYcofehYmt16u01DCXhHsNzw3Q=; b=gzdhkY5WWJuCVQo3GZbpcKMmaZMpV2Fqd9spDbX493E7BsL8+d7UPTczYCUIFdeWdwsUTd u93z0NJtdbXrUWMBPekE6Qn2Q6c6Fx/6OhrpHO0kjF3j/LPIiat4fpeDV7itlv0sBk1iWC r0hre3OHNowa7phFxT+D0iUpiZDgM3c= 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-379-pdE11Dc9PHGaX-ZduD-yQA-1; Tue, 07 Jan 2020 07:02:41 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5E97410054E3 for ; Tue, 7 Jan 2020 12:02:40 +0000 (UTC) Received: from redhat.com (ovpn-112-61.ams2.redhat.com [10.36.112.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 162265C1B0; Tue, 7 Jan 2020 12:02:31 +0000 (UTC) Date: Tue, 7 Jan 2020 12:02:29 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Dr. David Alan Gilbert (git)" Subject: Re: [PATCH 087/104] virtiofsd: prevent fv_queue_thread() vs virtio_loop() races Message-ID: <20200107120229.GB3368802@redhat.com> References: <20191212163904.159893-1-dgilbert@redhat.com> <20191212163904.159893-88-dgilbert@redhat.com> MIME-Version: 1.0 In-Reply-To: <20191212163904.159893-88-dgilbert@redhat.com> User-Agent: Mutt/1.12.1 (2019-06-15) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-MC-Unique: pdE11Dc9PHGaX-ZduD-yQA-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.81 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: qemu-devel@nongnu.org, stefanha@redhat.com, vgoyal@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Dec 12, 2019 at 04:38:47PM +0000, Dr. David Alan Gilbert (git) wrot= e: > From: Stefan Hajnoczi >=20 > We call into libvhost-user from the virtqueue handler thread and the > vhost-user message processing thread without a lock. There is nothing > protecting the virtqueue handler thread if the vhost-user message > processing thread changes the virtqueue or memory table while it is > running. >=20 > This patch introduces a read-write lock. Virtqueue handler threads are > readers. The vhost-user message processing thread is a writer. This > will allow concurrency for multiqueue in the future while protecting > against fv_queue_thread() vs virtio_loop() races. >=20 > Note that the critical sections could be made smaller but it would be > more invasive and require libvhost-user changes. Let's start simple and > improve performance later, if necessary. Another option would be an > RCU-style approach with lighter-weight primitives. >=20 > Signed-off-by: Stefan Hajnoczi > Merged with log changes > pull request 12 Two extraneous lines > --- > tools/virtiofsd/fuse_virtio.c | 34 +++++++++++++++++++++++++++++++++- > 1 file changed, 33 insertions(+), 1 deletion(-) Reviewed-by: Daniel P. Berrang=C3=A9 Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|