From patchwork Tue Dec 15 17:54:25 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Bonzini X-Patchwork-Id: 1416636 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Authentication-Results: ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=nongnu.org (client-ip=209.51.188.17; helo=lists.gnu.org; envelope-from=qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org; receiver=) Authentication-Results: ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256 header.s=mimecast20190719 header.b=WIVO+Ypb; dkim-atps=neutral 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 ozlabs.org (Postfix) with ESMTPS id 4CwR7C08bRz9sSf for ; Wed, 16 Dec 2020 05:07:34 +1100 (AEDT) Received: from localhost ([::1]:52548 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kpEjT-00028E-Qm for incoming@patchwork.ozlabs.org; Tue, 15 Dec 2020 13:07:31 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:34292) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kpEXU-0003Fd-Mj for qemu-devel@nongnu.org; Tue, 15 Dec 2020 12:55:10 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:59908) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kpEXM-0001Vt-2u for qemu-devel@nongnu.org; Tue, 15 Dec 2020 12:55:08 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1608054899; 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=kxCbnPEEv38iUxN9AvU/eo0lyndngsqISZ836jAvFo0=; b=WIVO+YpbLIWCUYg5Yd4SBVPLdbtpp2k3/Gad8zNCfpdEwG9997i9Irp/ZdI5RGvupYZljm HtzWIfvuP+aJVdEhG/2HyK7ece6aHUHiESXDMrMsXgLp5dYDkTjIw+g4jLchXqcAVQYtCH /DLZsYpkcZtzFYFquUlpUmDO/a5/GFo= 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-347-g8wnMU1gMEK11jlmVJV95w-1; Tue, 15 Dec 2020 12:54:57 -0500 X-MC-Unique: g8wnMU1gMEK11jlmVJV95w-1 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 CB51A51082 for ; Tue, 15 Dec 2020 17:54:56 +0000 (UTC) Received: from virtlab701.virt.lab.eng.bos.redhat.com (virtlab701.virt.lab.eng.bos.redhat.com [10.19.152.228]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8B21D5C1C4; Tue, 15 Dec 2020 17:54:56 +0000 (UTC) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PULL 25/45] scsi: fix device removal race vs IO restart callback on resume Date: Tue, 15 Dec 2020 12:54:25 -0500 Message-Id: <20201215175445.1272776-26-pbonzini@redhat.com> In-Reply-To: <20201215175445.1272776-1-pbonzini@redhat.com> References: <20201215175445.1272776-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Received-SPF: pass client-ip=216.205.24.124; envelope-from=pbonzini@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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: Maxim Levitsky Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: "Qemu-devel" From: Maxim Levitsky There is (mostly theoretical) race between removal of a scsi device and scsi_dma_restart_bh. It used to be easier to hit this race prior to my / Paulo's patch series that added rcu to scsi bus device handling code, but IMHO this race should still be possible to hit, at least in theory. Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1854811 Fix it anyway with a patch that was proposed by Paulo in the above bugzilla. Suggested-by: Paolo Bonzini Signed-off-by: Maxim Levitsky Message-Id: <20201210125929.1136390-2-mlevitsk@redhat.com> Signed-off-by: Paolo Bonzini --- hw/scsi/scsi-bus.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/hw/scsi/scsi-bus.c b/hw/scsi/scsi-bus.c index b901e701f0..edb5c3492a 100644 --- a/hw/scsi/scsi-bus.c +++ b/hw/scsi/scsi-bus.c @@ -170,6 +170,8 @@ static void scsi_dma_restart_bh(void *opaque) scsi_req_unref(req); } aio_context_release(blk_get_aio_context(s->conf.blk)); + /* Drop the reference that was acquired in scsi_dma_restart_cb */ + object_unref(OBJECT(s)); } void scsi_req_retry(SCSIRequest *req) @@ -188,6 +190,8 @@ static void scsi_dma_restart_cb(void *opaque, int running, RunState state) } if (!s->bh) { AioContext *ctx = blk_get_aio_context(s->conf.blk); + /* The reference is dropped in scsi_dma_restart_bh.*/ + object_ref(OBJECT(s)); s->bh = aio_bh_new(ctx, scsi_dma_restart_bh, s); qemu_bh_schedule(s->bh); }