From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756220Ab3AHCJy (ORCPT ); Mon, 7 Jan 2013 21:09:54 -0500 Received: from mail-we0-f177.google.com ([74.125.82.177]:65391 "EHLO mail-we0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756203Ab3AHCJw (ORCPT ); Mon, 7 Jan 2013 21:09:52 -0500 From: Frederic Weisbecker To: LKML Cc: Frederic Weisbecker , Alessio Igor Bogani , Andrew Morton , Chris Metcalf , Christoph Lameter , Geoff Levand , Gilad Ben Yossef , Hakan Akkan , Ingo Molnar , Li Zhong , Namhyung Kim , "Paul E. McKenney" , Paul Gortmaker , Peter Zijlstra , Steven Rostedt , Thomas Gleixner Subject: [PATCH 30/33] sched: Debug nohz rq clock Date: Tue, 8 Jan 2013 03:08:30 +0100 Message-Id: <1357610913-1080-31-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1357610913-1080-1-git-send-email-fweisbec@gmail.com> References: <1357610913-1080-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The runqueue clock is supposed to be periodically updated by the tick. On full dynticks CPU we call update_nohz_rq_clock() before reading it. Now the scheduler code is complicated enough that we may miss some update_nohz_rq_clock() calls before reading the runqueue clock. This therefore introduce a new debugging feature that detects when the rq clock is stale due to missing updates on full dynticks CPUs. This can be later expanded to debug stale clocks on dynticks-idle CPUs. Signed-off-by: Frederic Weisbecker Cc: Alessio Igor Bogani Cc: Andrew Morton Cc: Chris Metcalf Cc: Christoph Lameter Cc: Geoff Levand Cc: Gilad Ben Yossef Cc: Hakan Akkan Cc: Ingo Molnar Cc: Li Zhong Cc: Namhyung Kim Cc: Paul E. McKenney Cc: Paul Gortmaker Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner --- kernel/sched/sched.h | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index e1bac76..0fef0b3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -502,16 +502,39 @@ DECLARE_PER_CPU(struct rq, runqueues); #define cpu_curr(cpu) (cpu_rq(cpu)->curr) #define raw_rq() (&__raw_get_cpu_var(runqueues)) +static inline void rq_clock_check(struct rq *rq) +{ +#if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_NO_HZ_FULL) + unsigned long long clock; + unsigned long flags; + int cpu; + + cpu = cpu_of(rq); + if (!tick_nohz_full_cpu(cpu) || rq->curr == rq->idle) + return; + + local_irq_save(flags); + clock = sched_clock_cpu(cpu_of(rq)); + local_irq_restore(flags); + + if (abs(clock - rq->clock) > (TICK_NSEC * 3)) + WARN_ON_ONCE(1); +#endif +} + static inline u64 rq_clock(struct rq *rq) { + rq_clock_check(rq); return rq->clock; } static inline u64 rq_clock_task(struct rq *rq) { + rq_clock_check(rq); return rq->clock_task; } + #ifdef CONFIG_SMP #define rcu_dereference_check_sched_domain(p) \ -- 1.7.5.4