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.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 smtp.lore.kernel.org (Postfix) with ESMTPS id 108DAC4167B for ; Fri, 1 Dec 2023 16:49:44 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1r96h4-0000a7-Lp; Fri, 01 Dec 2023 11:48:46 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r96h2-0000Zc-EH for qemu-devel@nongnu.org; Fri, 01 Dec 2023 11:48:45 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1r96h0-0005Fk-R2 for qemu-devel@nongnu.org; Fri, 01 Dec 2023 11:48:44 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1701449321; 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=c6eb4jKXFUSrpEn38V31y8459yUzTVZs3T8NahHPtp4=; b=Er0hSBai7RZzZmJDQzJ5oQtutztl5aLpCLTEHS7eTU3t1kLe9qKwFSYY7bPl0/5ApyueeG kfMakv6g64SevHprz9HS9QXcIF7xJB6ufGc7YSoW//4onduEHxpAjrC8vUmxz9OQrER8Qq TxieA+6dRUW6vOH5X09nd6197GCqQmk= Received: from mimecast-mx02.redhat.com (mx-ext.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-477-UydhBTpEMz6pRb1cRCJaRg-1; Fri, 01 Dec 2023 11:48:38 -0500 X-MC-Unique: UydhBTpEMz6pRb1cRCJaRg-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (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 6D8AA2803027; Fri, 1 Dec 2023 16:48:38 +0000 (UTC) Received: from redhat.com (unknown [10.39.194.98]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 37787492BFE; Fri, 1 Dec 2023 16:48:37 +0000 (UTC) Date: Fri, 1 Dec 2023 17:48:36 +0100 From: Kevin Wolf To: Stefan Hajnoczi Cc: qemu-devel@nongnu.org, "Michael S. Tsirkin" , David Hildenbrand , Philippe =?iso-8859-1?Q?Mathieu-Daud=E9?= , Peter Xu , Paolo Bonzini , Fam Zheng Subject: Re: [PATCH 4/4] dma-helpers: don't lock AioContext in dma_blk_cb() Message-ID: References: <20231123194931.171598-1-stefanha@redhat.com> <20231123194931.171598-5-stefanha@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231123194931.171598-5-stefanha@redhat.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 23.11.2023 um 20:49 hat Stefan Hajnoczi geschrieben: > Commit abfcd2760b3e ("dma-helpers: prevent dma_blk_cb() vs > dma_aio_cancel() race") acquired the AioContext lock inside dma_blk_cb() > to avoid a race with scsi_device_purge_requests() running in the main > loop thread. > > The SCSI code no longer calls dma_aio_cancel() from the main loop thread > while I/O is running in the IOThread AioContext. Therefore it is no > longer necessary to take this lock to protect DMAAIOCB fields. The > ->cb() function also does not require the lock because blk_aio_*() and > friends do not need the AioContext lock. > > Both hw/ide/core.c and hw/ide/macio.c also call dma_blk_io() but don't > rely on it taking the AioContext lock, so this change is safe. > > Signed-off-by: Stefan Hajnoczi The commit message neglects to talk about dbs->io_func, which is what took the AioContext lock even before commit abfcd2760b3e. I think the reason is the same as for the previous patch. Reviewed-by: Kevin Wolf