From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755012Ab1HOPxv (ORCPT ); Mon, 15 Aug 2011 11:53:51 -0400 Received: from mail-vw0-f46.google.com ([209.85.212.46]:46598 "EHLO mail-vw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754964Ab1HOPxt (ORCPT ); Mon, 15 Aug 2011 11:53:49 -0400 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Andrew Morton , Anton Blanchard , Avi Kivity , Ingo Molnar , Lai Jiangshan , "Paul E . McKenney" , Paul Menage , Peter Zijlstra , Stephen Hemminger , Thomas Gleixner , Tim Pepper Subject: [PATCH 20/32] nohz/cpuset: Restart the tick if printk needs it Date: Mon, 15 Aug 2011 17:52:17 +0200 Message-Id: <1313423549-27093-21-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1313423549-27093-1-git-send-email-fweisbec@gmail.com> References: <1313423549-27093-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If we are in nohz adaptive mode and printk is called, the tick is missing to wake up the logger. We need to restart the tick when that happens. Signed-off-by: Frederic Weisbecker Cc: Andrew Morton Cc: Anton Blanchard Cc: Avi Kivity Cc: Ingo Molnar Cc: Lai Jiangshan Cc: Paul E . McKenney Cc: Paul Menage Cc: Peter Zijlstra Cc: Stephen Hemminger Cc: Thomas Gleixner Cc: Tim Pepper --- kernel/printk.c | 17 ++++++++++++++++- 1 files changed, 16 insertions(+), 1 deletions(-) diff --git a/kernel/printk.c b/kernel/printk.c index 3518539..aff07f0 100644 --- a/kernel/printk.c +++ b/kernel/printk.c @@ -41,6 +41,7 @@ #include #include #include +#include #include @@ -1220,8 +1221,22 @@ int printk_needs_cpu(int cpu) void wake_up_klogd(void) { - if (waitqueue_active(&log_wait)) + unsigned long flags; + + if (waitqueue_active(&log_wait)) { this_cpu_write(printk_pending, 1); + /* Make it visible from any interrupt from now */ + barrier(); + /* + * It's safe to check that even if interrupts are not disabled. + * If we enable nohz adaptive mode concurrently, we'll the + * printk_pending value and thus keep a periodic tick behaviour. + * Unless it's possible tick_nohz_adaptive_mode() reads its value + * before the barrier() ? + */ + if (tick_nohz_adaptive_mode()) + smp_cpuset_update_nohz(smp_processor_id()); + } } /** -- 1.7.5.4