From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753122Ab0HIRNw (ORCPT ); Mon, 9 Aug 2010 13:13:52 -0400 Received: from e7.ny.us.ibm.com ([32.97.182.137]:38215 "EHLO e7.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750989Ab0HIRNu (ORCPT ); Mon, 9 Aug 2010 13:13:50 -0400 Date: Mon, 9 Aug 2010 10:13:29 -0700 From: "Paul E. McKenney" To: Miles Lane Cc: LKML , oleg@redhat.com Subject: Re: 2.6.35 - INFO: kernel/signal.c:660 invoked rcu_dereference_check() without protection! Message-ID: <20100809171329.GF3026@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 03, 2010 at 11:18:07PM -0400, Miles Lane wrote: > [ INFO: suspicious rcu_dereference_check() usage. ] > --------------------------------------------------- > kernel/signal.c:660 invoked rcu_dereference_check() without protection! > > other info that might help us debug this: > > rcu_scheduler_active = 1, debug_locks = 1 > 1 lock held by udevd/670: > #0: (tasklist_lock){.+.+..}, at: [] do_exit+0x252/0x671 > stack backtrace: > Pid: 670, comm: udevd Not tainted 2.6.35 #15 > Call Trace: > [] lockdep_rcu_dereference+0x9d/0xa6 > [] check_kill_permission+0x9d/0x132 > [] group_send_sig_info+0x1a/0x3d > [] do_exit+0x34e/0x671 > [] do_group_exit+0x78/0xa3 > [] sys_exit_group+0x12/0x16 > [] system_call_fastpath+0x16/0x1b Thank you again for your testing efforts! This one is a bit odd. exit_signals() holds either the tasklist_lock or the ->sighand->siglock over its signal manipulations, so this is not the code path triggering the above. I might be missing something, but I don't see either hrtimer_cancel() or exit_itimers() attempting to send signals. I am copying Oleg, as he might see something that I am missing. Thanx, Paul