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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (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 BC5EDC4167B for ; Mon, 4 Dec 2023 14:51:18 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.647083.1009791 (Exim 4.92) (envelope-from ) id 1rAAHu-0001QT-IL; Mon, 04 Dec 2023 14:51:10 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 647083.1009791; Mon, 04 Dec 2023 14:51:10 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rAAHu-0001QM-FL; Mon, 04 Dec 2023 14:51:10 +0000 Received: by outflank-mailman (input) for mailman id 647083; Mon, 04 Dec 2023 14:51:09 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1rAAHt-0001Q8-48 for xen-devel@lists.xenproject.org; Mon, 04 Dec 2023 14:51:09 +0000 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 8df6a82c-92b4-11ee-98e5-6d05b1d4d9a1; Mon, 04 Dec 2023 15:51:08 +0100 (CET) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-595-7kVZWR21Pym7Nfk5yaUfnQ-1; Mon, 04 Dec 2023 09:51:04 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (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 mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6976685A59D; Mon, 4 Dec 2023 14:51:03 +0000 (UTC) Received: from localhost (unknown [10.39.192.49]) by smtp.corp.redhat.com (Postfix) with ESMTP id C43E440C6EB9; Mon, 4 Dec 2023 14:51:02 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 8df6a82c-92b4-11ee-98e5-6d05b1d4d9a1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701701466; 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=xEOIXWa0DaRIIsxxh+p/yqRV4ny33fxYNbdSCdVwz7E=; b=JJ0te5dURjetktuKM6aa8Gm4BKdjtXzGlSRyL8wQ/7txs8PI216obBMk/jCrf5Gy2ENO+4 lNxKZBwXYbnIZVl3om3C6cwH7oXHwWoiSCJxPM1XhMZzt+6OGy7Oy3dHCmzC1JAEzGZHGx LW0URNtHrAhuTwSGrgBSm+FSblEt/7E= X-MC-Unique: 7kVZWR21Pym7Nfk5yaUfnQ-1 Date: Mon, 4 Dec 2023 09:51:01 -0500 From: Stefan Hajnoczi To: Kevin Wolf Cc: qemu-devel@nongnu.org, Hanna Reitz , Paul Durrant , Paolo Bonzini , Alberto Garcia , Emanuele Giuseppe Esposito , John Snow , Eric Blake , Wen Congyang , qemu-block@nongnu.org, xen-devel@lists.xenproject.org, Coiby Xu , Eduardo Habkost , Xie Changlong , Ari Sundholm , Li Zhijian , Cleber Rosa , Juan Quintela , "Michael S. Tsirkin" , Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= , Jason Wang , Vladimir Sementsov-Ogievskiy , Zhang Chen , Peter Xu , Anthony Perard , Stefano Stabellini , Leonardo Bras , Pavel Dovgalyuk , Fam Zheng , Fabiano Rosas Subject: Re: [PATCH 01/12] virtio-scsi: replace AioContext lock with tmf_bh_lock Message-ID: <20231204145101.GB1492005@fedora> References: <20231129195553.942921-1-stefanha@redhat.com> <20231129195553.942921-2-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="mjl6rdY6Uz2gkcPm" Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 --mjl6rdY6Uz2gkcPm Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Dec 04, 2023 at 01:46:13PM +0100, Kevin Wolf wrote: > Am 29.11.2023 um 20:55 hat Stefan Hajnoczi geschrieben: > > Protect the Task Management Function BH state with a lock. The TMF BH > > runs in the main loop thread. An IOThread might process a TMF at the > > same time as the TMF BH is running. Therefore tmf_bh_list and tmf_bh > > must be protected by a lock. > >=20 > > Run TMF request completion in the IOThread using aio_wait_bh_oneshot(). > > This avoids more locking to protect the virtqueue and SCSI layer state. > >=20 > > Signed-off-by: Stefan Hajnoczi >=20 > The second part reminds me that the implicit protection of the virtqueue > and SCSI data structures by having all accesses in a single thread is > hard to review and I think we wanted to put some assertions there to > check that we're really running in the right thread. I don't think we > have done that so far, so I suppose after this patch would be the place > in the series to add them, before we remove the protection by the > AioContext lock? Thanks for reminding me. I will add assertions in the next revision of this series. 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