Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755221Ab2HaXwg (ORCPT ); Fri, 31 Aug 2012 19:52:36 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:48735 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752319Ab2HaXwf (ORCPT ); Fri, 31 Aug 2012 19:52:35 -0400 X-Originating-IP: 217.70.178.133 X-Originating-IP: 173.246.103.110 Date: Fri, 31 Aug 2012 16:52:25 -0700 From: Josh Triplett 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, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, fweisbec@gmail.com, sbw@mit.edu, patches@linaro.org, Alessio Igor Bogani , Avi Kivity , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , "H. Peter Anvin" , Ingo Molnar , Kevin Hilman , Max Krasnyansky , Stephen Hemminger , Sven-Thorsten Dietrich Subject: Re: [PATCH tip/core/rcu 11/26] rcu: Exit RCU extended QS on user preemption Message-ID: <20120831235225.GH11771@jtriplet-mobl1> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346360743-3628-11-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1346360743-3628-11-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2416 Lines: 68 On Thu, Aug 30, 2012 at 02:05:28PM -0700, Paul E. McKenney wrote: > From: Frederic Weisbecker > > When exceptions or irq are about to resume userspace, if > the task needs to be rescheduled, the arch low level code > calls schedule() directly. > > At that time we may be in extended quiescent state from RCU > POV: the exception is not anymore protected inside > rcu_user_exit() - rcu_user_enter() and the irq has called > rcu_irq_exit() already. > > Create a new API schedule_user() that calls schedule() inside > rcu_user_exit()-rcu_user_enter() in order to protect it. Archs > will need to rely on it now to implement user preemption safely. > > Signed-off-by: Frederic Weisbecker > Cc: Alessio Igor Bogani > Cc: Andrew Morton > Cc: Avi Kivity > Cc: Chris Metcalf > Cc: Christoph Lameter > Cc: Geoff Levand > Cc: Gilad Ben Yossef > Cc: Hakan Akkan > Cc: H. Peter Anvin > Cc: Ingo Molnar > Cc: Josh Triplett > Cc: Kevin Hilman > Cc: Max Krasnyansky > Cc: Peter Zijlstra > Cc: Stephen Hemminger > Cc: Steven Rostedt > Cc: Sven-Thorsten Dietrich > Cc: Thomas Gleixner > Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett > kernel/sched/core.c | 7 +++++++ > 1 files changed, 7 insertions(+), 0 deletions(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index 0bd599b..e841dfc 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3463,6 +3463,13 @@ asmlinkage void __sched schedule(void) > } > EXPORT_SYMBOL(schedule); > > +asmlinkage void __sched schedule_user(void) > +{ > + rcu_user_exit(); > + schedule(); > + rcu_user_enter(); > +} > + > /** > * schedule_preempt_disabled - called with preemption disabled > * > -- > 1.7.8 > -- 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/