Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932099AbaKUO7g (ORCPT ); Fri, 21 Nov 2014 09:59:36 -0500 Received: from mta-out1.inet.fi ([62.71.2.227]:54201 "EHLO jenni2.inet.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758147AbaKUO7f (ORCPT ); Fri, 21 Nov 2014 09:59:35 -0500 Date: Fri, 21 Nov 2014 16:58:17 +0200 From: "Kirill A. Shutemov" To: Pranith Kumar Cc: "Paul E. McKenney" , linux-kernel@vger.kernel.org, mingo@kernel.org, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com Subject: Re: [PATCH tip/core/rcu 3/9] drivers/md: Use rcu_dereference() for accessing rcu pointer Message-ID: <20141121145817.GA17710@node.dhcp.inet.fi> References: <20141028220944.GA26114@linux.vnet.ibm.com> <1414534202-27312-1-git-send-email-paulmck@linux.vnet.ibm.com> <1414534202-27312-3-git-send-email-paulmck@linux.vnet.ibm.com> <20141121133145.GA17245@node.dhcp.inet.fi> <546F4C8C.4040904@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <546F4C8C.4040904@gmail.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Nov 21, 2014 at 09:30:36AM -0500, Pranith Kumar wrote: > On 11/21/2014 08:31 AM, Kirill A. Shutemov wrote: > > On Tue, Oct 28, 2014 at 03:09:56PM -0700, Paul E. McKenney wrote: > >> From: Pranith Kumar > >> > >> Got Paul's email wrong the first time. > >> > >> The map field in 'struct mapped_device' is an rcu pointer. Use rcu_dereference() > >> while accessing it. > >> > >> Signed-off-by: Pranith Kumar > >> Signed-off-by: Paul E. McKenney > > > > On current -next I see this: > > > > [ 6.388264] =============================== > > [ 6.389571] [ INFO: suspicious RCU usage. ] > > [ 6.390869] 3.18.0-rc5-next-20141121-08303-g44cae4530372 #2 Not tainted > > [ 6.392185] ------------------------------- > > [ 6.393479] /home/kas/git/public/linux/drivers/md/dm.c:2853 suspicious rcu_dereference_check() usage! > > [ 6.394801] > > other info that might help us debug this: > > > > Hi Kirill, > > We are dereferencing an RCU pointer with the suspend_lock held which is causing this warning. > > Can you please check if the following patch helps? Thanks! Nope. The same issue. IIUC, the problem is that you dereference pointer outside rcu_read_lock() section, not that suspend_lock is held. -- Kirill A. Shutemov -- 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/