Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933847Ab0BHAvR (ORCPT ); Sun, 7 Feb 2010 19:51:17 -0500 Received: from smtp-out.google.com ([216.239.33.17]:43896 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757852Ab0BHAqe (ORCPT ); Sun, 7 Feb 2010 19:46:34 -0500 DomainKey-Signature: a=rsa-sha1; s=beta; d=google.com; c=nofws; q=dns; h=date:from:x-x-sender:to:cc:subject:in-reply-to:message-id: references:user-agent:mime-version:content-type:x-system-of-record; b=A3C6K7hq6nT04Kra85UEcwP7uwFgeVrNvk7fJftC+hIHzteXIMNCtQGRbNBLPupj3 mEiSGqRuuNZB8obqlBi8g== Date: Sun, 7 Feb 2010 16:46:25 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: "Eric W. Biederman" cc: "Rafael J. Wysocki" , Linux Kernel Mailing List , Kernel Testers List , Maciej Rutecki , Hugh Dickins Subject: Re: [Bug #15202] lockdep warning during elevator_switch In-Reply-To: Message-ID: References: <4Ht3jFrT7uE.A.JI.-nzbLB@chimera> <445R0ey9hAI.A.h3.RozbLB@chimera> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1499 Lines: 33 On Sun, 7 Feb 2010, Hugh Dickins wrote: > > This message has been generated automatically as a part of a summary report > > of recent regressions. > > > > The following bug entry is on the current list of known regressions > > from 2.6.32. Please verify if it still should be listed and let the tracking team > > know (either way). > > > > > > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=15202 > > Subject : lockdep warning during elevator_switch > > Submitter : Hugh Dickins > > Date : 2010-01-31 23:55 (8 days old) > > References : http://marc.info/?l=linux-kernel&m=126498212613051&w=4 > > Yes, still so in 2.6.33-rc7. > This type of lock dependency is always going to exist whenever a write to a sysfs file causes the kernel to remove its dirent. In this case, writing to /sys/devices/block/xxx/queue/scheduler takes sd->dep_map and sd->parent->dep_map via sysfs_get_active_two() to pin both via sysfs_write_file(). The call to kobject_del() removes its directory from the hierarchy which takes sd->dep_map in sysfs_deactivate() because of 846f99749a. Eric, do we need to preempt the rwsem from being acquired here when the dirent is already pinned because of a store to one of its files? -- 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/