From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761278AbZLPK0V (ORCPT ); Wed, 16 Dec 2009 05:26:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761244AbZLPK0S (ORCPT ); Wed, 16 Dec 2009 05:26:18 -0500 Received: from bombadil.infradead.org ([18.85.46.34]:41635 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761241AbZLPK0O (ORCPT ); Wed, 16 Dec 2009 05:26:14 -0500 Subject: Re: [PATCH RFC tip/core/rcu 14/18] rcu: lockdep check for exiting to user space as RCU reader From: Peter Zijlstra To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, dvhltc@us.ibm.com, niv@us.ibm.com, tglx@linutronix.de, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com In-Reply-To: <12609181612244-git-send-email-> References: <20091215230213.GA9093@linux.vnet.ibm.com> <12609181612244-git-send-email-> Content-Type: text/plain; charset="UTF-8" Date: Wed, 16 Dec 2009 11:24:42 +0100 Message-ID: <1260959082.17860.35.camel@laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2009-12-15 at 15:02 -0800, Paul E. McKenney wrote: > From: Paul E. McKenney > > Proposed for 2.6.34, not for inclusion. > > It is illegal to return to user-space execution while running within an > RCU read-side critical section. It turns out that CONFIG_TREE_PREEMPT_RCU > has enough information lying around to detect this, so add the checks > to lockdep (CONFIG_PROVE_LOCKING). But uhm, we already track the rcu read lock as a regular lockdep lock, so it should already check this, no?