Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754263AbZCKSOY (ORCPT ); Wed, 11 Mar 2009 14:14:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753500AbZCKSON (ORCPT ); Wed, 11 Mar 2009 14:14:13 -0400 Received: from g1t0027.austin.hp.com ([15.216.28.34]:24615 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753395AbZCKSOM (ORCPT ); Wed, 11 Mar 2009 14:14:12 -0400 Date: Wed, 11 Mar 2009 12:14:09 -0600 From: Alex Chiang To: Cornelia Huck Cc: Greg KH , Vegard Nossum , Pekka Enberg , Ingo Molnar , jbarnes@virtuousgeek.org, tj@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH, RFC] sysfs: only allow one scheduled removal callback per kobj Message-ID: <20090311181409.GB23138@ldl.fc.hp.com> Mail-Followup-To: Alex Chiang , Cornelia Huck , Greg KH , Vegard Nossum , Pekka Enberg , Ingo Molnar , jbarnes@virtuousgeek.org, tj@kernel.org, linux-kernel@vger.kernel.org References: <20090310232027.GC25665@ldl.fc.hp.com> <20090311044151.GB25840@suse.de> <20090311070359.GF25665@ldl.fc.hp.com> <20090311153228.GA21217@suse.de> <20090311184729.110761e4@gondolin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090311184729.110761e4@gondolin> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1548 Lines: 40 * Cornelia Huck : > On Wed, 11 Mar 2009 08:32:28 -0700, > Greg KH wrote: > > > Why can't you use device_unregister()? Or, you could use device_del(), > > which lets you rely on the fact that the device structure is still > > around for a bit, but it will disappear from sysfs. Just don't forget > > to do the final put_device() on it to free the memory and "really" > > release it. > > > > Or am I missing something else here? > > You can't unregister a device from one of its attribute callbacks, it > locks up in sysfs (removing the sysfs dir waits for all active > references to be dropped, but the reference obtained before calling > ->store won't be dropped until after ->store returned...) > device_schedule_callback() was introduced to solve exactly that problem. Yes, that is exactly why I used device_schedule_callback. > (For the original oops, I'd rather solve the problem by making sure the > caller doesn't trigger removal several times - should probably be less > code than the proposed patch?) The scsi stuff [sdev_store_delete()] is susceptible to exactly the same problem. I could put the "only allow one removal per kobj" code into my specific code path, but I think it makes more sense to put it in the common code. Thanks. /ac -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/