From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752531AbcF2BYh (ORCPT ); Tue, 28 Jun 2016 21:24:37 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56446 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752455AbcF2BYh (ORCPT ); Tue, 28 Jun 2016 21:24:37 -0400 Date: Wed, 29 Jun 2016 09:24:15 +0800 From: Fam Zheng To: Christoph Hellwig Cc: linux-kernel@vger.kernel.org, "Michael S. Tsirkin" , virtualization@lists.linux-foundation.org Subject: Re: [PATCH] virtio-blk: Generate uevent after attribute available Message-ID: <20160629012414.GA23296@ad.usersys.redhat.com> References: <20160628023915.6012-1-famz@redhat.com> <20160628114553.GA18354@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20160628114553.GA18354@infradead.org> User-Agent: Mutt/1.6.1 (2016-04-27) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.28]); Wed, 29 Jun 2016 01:24:22 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 06/28 04:45, Christoph Hellwig wrote: > On Tue, Jun 28, 2016 at 10:39:15AM +0800, Fam Zheng wrote: > > Userspace listens to the KOBJ_ADD uevent generated in add_disk. At that > > point we haven't created the serial attribute file, therefore depending > > on how fast udev reacts, the /dev/disk/by-id/ entry doesn't always get > > created. > > > > This race condition can be easily reproduced by hot plugging a number of > > virtio-blk disks. > > > > Also in systemd, there used to be a related workaround in udev rules > > called 'WAIT_FOR="serial"', but it is removed in later versions. > > > > Now let's generate a KOBJ_CHANGE event after the attributes are ready. > > The same race is present in other drivers as well, e.g. nvme. Please > find a way to make this work properly without needing to hack every > driver to send events manually. OK, I'll take a look today! Fam