From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757362Ab1GKUe6 (ORCPT ); Mon, 11 Jul 2011 16:34:58 -0400 Received: from mail-ew0-f46.google.com ([209.85.215.46]:52606 "EHLO mail-ew0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756001Ab1GKUen (ORCPT ); Mon, 11 Jul 2011 16:34:43 -0400 From: Frederic Weisbecker To: "Paul E. McKenney" Cc: LKML , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" Subject: [PATCH 2/3] x86: Enter rcu extended qs after idle notifier call Date: Mon, 11 Jul 2011 22:34:31 +0200 Message-Id: <1310416472-2554-3-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1310416472-2554-1-git-send-email-fweisbec@gmail.com> References: <1310416472-2554-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The idle notifier, called by enter_idle(), enters into rcu read side critical section but at that time we already switched into rcu dynticks idle mode. And it's illegal to use rcu_read_lock() in that state. This results in rcu reporting its bad mood: [ 1.275635] WARNING: at include/linux/rcupdate.h:194 __atomic_notifier_call_chain+0xd2/0x110() [ 1.275635] Hardware name: AMD690VM-FMH [ 1.275635] Modules linked in: [ 1.275635] Pid: 0, comm: swapper Not tainted 3.0.0-rc6+ #252 [ 1.275635] Call Trace: [ 1.275635] [] warn_slowpath_common+0x7a/0xb0 [ 1.275635] [] warn_slowpath_null+0x15/0x20 [ 1.275635] [] __atomic_notifier_call_chain+0xd2/0x110 [ 1.275635] [] atomic_notifier_call_chain+0x11/0x20 [ 1.275635] [] enter_idle+0x20/0x30 [ 1.275635] [] cpu_idle+0xa5/0x110 [ 1.275635] [] rest_init+0xe5/0x140 [ 1.275635] [] ? rest_init+0x48/0x140 [ 1.275635] [] start_kernel+0x3d1/0x3dc [ 1.275635] [] x86_64_start_reservations+0x131/0x135 [ 1.275635] [] x86_64_start_kernel+0xed/0xf4 [ 1.275635] ---[ end trace a22d306b065d4a66 ]--- Fix this by entering rcu extended quiescent state later, just before the CPU goes to sleep. Signed-off-by: Frederic Weisbecker Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Thomas Gleixner Cc: H. Peter Anvin --- arch/x86/kernel/process_64.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index 4f3cb3e..df5f83d 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -120,7 +120,7 @@ void cpu_idle(void) /* endless idle loop with no priority at all */ while (1) { - tick_nohz_enter_idle(); + tick_nohz_stop_sched_tick(1); while (!need_resched()) { rmb(); @@ -136,7 +136,12 @@ void cpu_idle(void) enter_idle(); /* Don't trace irqs off for idle */ stop_critical_timings(); + + /* enter_idle() needs rcu for notifiers */ + rcu_enter_nohz(); pm_idle(); + rcu_exit_nohz(); + start_critical_timings(); /* In many cases the interrupt that ended idle @@ -145,7 +150,7 @@ void cpu_idle(void) __exit_idle(); } - tick_nohz_exit_idle(); + tick_nohz_restart_sched_tick(); preempt_enable_no_resched(); schedule(); preempt_disable(); -- 1.7.5.4