From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail191.messagelabs.com (mail191.messagelabs.com [216.82.242.19]) by kanga.kvack.org (Postfix) with ESMTP id 5D3AE6B0012 for ; Wed, 11 May 2011 19:12:19 -0400 (EDT) Subject: Re: 2.6.39-rc6-mmotm0506 - lockdep splat in RCU code on page fault In-Reply-To: Your message of "Tue, 10 May 2011 01:20:29 PDT." <20110510082029.GF2258@linux.vnet.ibm.com> From: Valdis.Kletnieks@vt.edu References: <6921.1304989476@localhost> <20110510082029.GF2258@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1305155494_2793P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Wed, 11 May 2011 19:11:34 -0400 Message-ID: <34783.1305155494@localhost> Sender: owner-linux-mm@kvack.org List-ID: To: paulmck@linux.vnet.ibm.com Cc: Andrew Morton , Ingo Molnar , Peter Zijlstra , linux-kernel@vger.kernel.org, linux-mm@kvack.org --==_Exmh_1305155494_2793P Content-Type: text/plain; charset=us-ascii On Tue, 10 May 2011 01:20:29 PDT, "Paul E. McKenney" said: Would test, but it doesn't apply cleanly to my -mmotm0506 tree: > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > index 5616b17..20c22c5 100644 > --- a/kernel/rcutree.c > +++ b/kernel/rcutree.c > @@ -1525,13 +1525,15 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt) > */ > static void rcu_cpu_kthread_timer(unsigned long arg) > { > - unsigned long flags; > + unsigned long old; > + unsigned long new; > struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg); > struct rcu_node *rnp = rdp->mynode; > > - raw_spin_lock_irqsave(&rnp->lock, flags); > - rnp->wakemask |= rdp->grpmask; > - raw_spin_unlock_irqrestore(&rnp->lock, flags); > + do { > + old = rnp->wakemask; > + new = old | rdp->grpmask; > + } while (cmpxchg(&rnp->wakemask, old, new) != old); > invoke_rcu_node_kthread(rnp); > } My source has this: raw_spin_lock_irqsave(&rnp->lock, flags); rnp->wakemask |= rdp->grpmask; invoke_rcu_node_kthread(rnp); raw_spin_unlock_irqrestore(&rnp->lock, flags); the last 2 lines swapped from what you diffed against. I can easily work around that, except it's unclear what the implications of the invoke_rcu moving outside of the irq save/restore pair (or if it being inside is the actual root cause)... --==_Exmh_1305155494_2793P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFNyxemcC3lWbTT17ARAhTcAKDq4c+9o0tv6pWdVzsGNS5JCHwu+wCgpWnJ DZZAx2bdmaeLxXBAC2I8yLw= =2YiI -----END PGP SIGNATURE----- --==_Exmh_1305155494_2793P-- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org