From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755298Ab2HaXyX (ORCPT ); Fri, 31 Aug 2012 19:54:23 -0400 Received: from relay4-d.mail.gandi.net ([217.70.183.196]:41472 "EHLO relay4-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754995Ab2HaXyW (ORCPT ); Fri, 31 Aug 2012 19:54:22 -0400 X-Originating-IP: 217.70.178.146 X-Originating-IP: 173.246.103.110 Date: Fri, 31 Aug 2012 16:54:12 -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 13/26] x86: Exit RCU extended QS on notify resume Message-ID: <20120831235412.GJ11771@jtriplet-mobl1> References: <20120830210520.GA2824@linux.vnet.ibm.com> <1346360743-3628-1-git-send-email-paulmck@linux.vnet.ibm.com> <1346360743-3628-13-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: <1346360743-3628-13-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 On Thu, Aug 30, 2012 at 02:05:30PM -0700, Paul E. McKenney wrote: > From: Frederic Weisbecker > > do_notify_resume() may be called on irq or exception > exit. But at that time the exception has already called > rcu_user_enter() and the irq has already called rcu_irq_exit(). > > Since it can use RCU read side critical section, we must call > rcu_user_exit() before doing anything there. Then we must call > back rcu_user_enter() after this function because we know we are > going to userspace from there. > > This complete support for userspace RCU extended quiescent state > in x86-64. > > 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 > arch/x86/Kconfig | 1 + > arch/x86/kernel/signal.c | 4 ++++ > 2 files changed, 5 insertions(+), 0 deletions(-) > > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig > index ba2657c..5cd953a 100644 > --- a/arch/x86/Kconfig > +++ b/arch/x86/Kconfig > @@ -97,6 +97,7 @@ config X86 > select KTIME_SCALAR if X86_32 > select GENERIC_STRNCPY_FROM_USER > select GENERIC_STRNLEN_USER > + select HAVE_RCU_USER_QS if X86_64 > > config INSTRUCTION_DECODER > def_bool (KPROBES || PERF_EVENTS || UPROBES) > diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c > index b280908..bca0ab9 100644 > --- a/arch/x86/kernel/signal.c > +++ b/arch/x86/kernel/signal.c > @@ -779,6 +779,8 @@ static void do_signal(struct pt_regs *regs) > void > do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) > { > + rcu_user_exit(); > + > #ifdef CONFIG_X86_MCE > /* notify userspace of pending MCEs */ > if (thread_info_flags & _TIF_MCE_NOTIFY) > @@ -804,6 +806,8 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags) > #ifdef CONFIG_X86_32 > clear_thread_flag(TIF_IRET); > #endif /* CONFIG_X86_32 */ > + > + rcu_user_enter(); > } > > void signal_fault(struct pt_regs *regs, void __user *frame, char *where) > -- > 1.7.8 >