From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754579Ab2D3PnK (ORCPT ); Mon, 30 Apr 2012 11:43:10 -0400 Received: from acsinet15.oracle.com ([141.146.126.227]:29346 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752881Ab2D3PnI (ORCPT ); Mon, 30 Apr 2012 11:43:08 -0400 Date: Mon, 30 Apr 2012 11:37:23 -0400 From: Konrad Rzeszutek Wilk To: gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: udev races with 'arch_register_cpu' to write 1 to /sys/devices/system/cpu/cpu1/online (which is not yet created). Message-ID: <20120430153723.GB23485@phenom.dumpdata.com> References: <20120430153623.GA23485@phenom.dumpdata.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120430153623.GA23485@phenom.dumpdata.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-Source-IP: acsinet21.oracle.com [141.146.126.237] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 30, 2012 at 11:36:23AM -0400, Konrad Rzeszutek Wilk wrote: > Hey Greg, Grr.. Incorrectly added LKML to it. Sorry about that. > > Hoping you can help with some guidance on how to fix this. > > The issue is with CPU hotplug is that when a CPU goes up > it calls 'arch_register_cpu' which eventually calls > register_cpu. That function does these two things: > > 251 error = device_register(&cpu->dev); > 252 if (!error && cpu->hotpluggable) > 253 register_cpu_control(cpu); > > and the device_register creates a nice little SysFS directory: > > /sys/devices/system/cpu/cpu2/ which at line 251 has the 'add' attribute > but no 'online' attribute. udev then tries to echo 1 to the 'online' > and it we get: > udevd-work[2421]: error opening ATTR{/sys/devices/system/cpu/cpu2/online} for writing: No such file or directory > > Line 253 creates said 'online' and at that time udev [or the system admin] > can write 1 to 'online' and the CPU goes up. > > So .. any thoughts? Is there some way to inhibit from uevent being sent > until line 253 has run? >