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 0E856C4332F for ; Tue, 8 Nov 2022 14:14:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1osPMS-0004h4-Sv; Tue, 08 Nov 2022 09:13:56 -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 1osPMQ-0004bU-V2 for qemu-devel@nongnu.org; Tue, 08 Nov 2022 09:13:54 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1osPMP-0002y2-H1 for qemu-devel@nongnu.org; Tue, 08 Nov 2022 09:13:54 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1667916833; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=NWjGOLQWLUbZG057Q/jP0mTSXtmCsUsVa6DAPKbRCK8=; b=AGpzMrKZVYv5VlPJJUGY9UnrwkGDkjBnYDL0dtcRCGdd1rDw+HQBKTybZrNgG3oekbxZvB int540TDAKo1j6MHWCYF7OHRvEYKwDSmrbverJWqBuNIlWTtLXVhd69kEW1JXSViCP9TJt 6IMM3jp3PT0fI/YqAw6ncCLP9hEZFks= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-616-oUsaQR3_Na2D1P3J2eP3sg-1; Tue, 08 Nov 2022 09:13:49 -0500 X-MC-Unique: oUsaQR3_Na2D1P3J2eP3sg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 5FDEC833A0E; Tue, 8 Nov 2022 14:13:49 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.118]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6C24AC15BB5; Tue, 8 Nov 2022 14:13:48 +0000 (UTC) Date: Tue, 8 Nov 2022 15:13:46 +0100 From: Kevin Wolf To: Hanna Reitz Cc: qemu-block@nongnu.org, qemu-devel@nongnu.org, Stefan Hajnoczi Subject: Re: [PATCH v2 0/3] block: Start/end drain on correct AioContext Message-ID: References: <20221107151321.211175-1-hreitz@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20221107151321.211175-1-hreitz@redhat.com> X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Received-SPF: pass client-ip=170.10.133.124; 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_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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 07.11.2022 um 16:13 hat Hanna Reitz geschrieben: > Hi, > > v1 cover letter: > https://lists.nongnu.org/archive/html/qemu-block/2022-09/msg00389.html > > bdrv_replace_child_noperm() drains the child via > bdrv_parent_drained_{begin,end}_single(). When it removes a child, the > bdrv_parent_drained_end_single() at its end will be called on an empty > child, making the BDRV_POLL_WHILE() in it poll the main AioContext > (because c->bs is NULL). > > That’s wrong, though, because it’s supposed to operate on the parent. > bdrv_parent_drained_end_single_no_poll() will have scheduled any BHs in > the parents’ AioContext, which may be anything, not necessarily the main > context. Therefore, we must poll the parent’s context. > > Patch 3 does this for both bdrv_parent_drained_{begin,end}_single(). > Patch 1 ensures that we can legally call > bdrv_child_get_parent_aio_context() from those I/O context functions, > and patch 2 fixes blk_do_set_aio_context() to not cause an assertion > failure if it beginning a drain can end up in blk_get_aio_context() > before blk->ctx has been updated. Hmm, I may have unintentionally made this series obsolete with the drain series I sent today. The poll instances that you're fixing simply don't exist any more after it. Can you check if the bug is gone with my series? I would hope so, but if not, we would probably need to apply a fix in a different place. Kevin