From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83F80C433E9 for ; Thu, 4 Mar 2021 12:00:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 455C860C3D for ; Thu, 4 Mar 2021 12:00:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239680AbhCDL7q (ORCPT ); Thu, 4 Mar 2021 06:59:46 -0500 Received: from mga04.intel.com ([192.55.52.120]:8070 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239682AbhCDL7m (ORCPT ); Thu, 4 Mar 2021 06:59:42 -0500 IronPort-SDR: UrnLBjMoHGx5EbNWMihUGN2hLj93FjDOvntr84cW3U/qiN3i/HYG25519sTA9tXK9kKMw38tRz 7AW3zPoQyTaA== X-IronPort-AV: E=McAfee;i="6000,8403,9912"; a="184989654" X-IronPort-AV: E=Sophos;i="5.81,222,1610438400"; d="scan'208";a="184989654" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2021 03:59:01 -0800 IronPort-SDR: VblYH86PkOAJfSht4+uTOTPNr/R/oWUW0zBJP7aRvjGaRGXI1E+bPeE0sycFlrtFS0P+ykApj1 iVy14uplVX2w== X-IronPort-AV: E=Sophos;i="5.81,222,1610438400"; d="scan'208";a="445704561" Received: from rjwysock-mobl1.ger.corp.intel.com (HELO [10.249.135.211]) ([10.249.135.211]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Mar 2021 03:58:56 -0800 Subject: Re: [PATCH tip/core/rcu 02/12] timer: Report ignored local enqueue in nohz mode To: paulmck@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, Frederic Weisbecker References: <20210304002225.GA23492@paulmck-ThinkPad-P72> <20210304002311.23655-2-paulmck@kernel.org> From: "Rafael J. Wysocki" Organization: Intel Technology Poland Sp. z o. o., KRS 101882, ul. Slowackiego 173, 80-298 Gdansk Message-ID: Date: Thu, 4 Mar 2021 12:58:54 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: <20210304002311.23655-2-paulmck@kernel.org> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/4/2021 1:23 AM, paulmck@kernel.org wrote: > From: Frederic Weisbecker > > Enqueuing a local timer after the tick has been stopped will result in > the timer being ignored until the next random interrupt. > > Perform sanity checks to report these situations. > > Cc: Peter Zijlstra > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: Rafael J. Wysocki > Signed-off-by: Frederic Weisbecker > Signed-off-by: Paul E. McKenney Reviewed-by: Rafael J. Wysocki > --- > kernel/sched/core.c | 24 +++++++++++++++++++++++- > 1 file changed, 23 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index ca2bb62..4822371 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -674,6 +674,26 @@ int get_nohz_timer_target(void) > return cpu; > } > > +static void wake_idle_assert_possible(void) > +{ > +#ifdef CONFIG_SCHED_DEBUG > + /* Timers are re-evaluated after idle IRQs */ > + if (in_hardirq()) > + return; > + /* > + * Same as hardirqs, assuming they are executing > + * on IRQ tail. Ksoftirqd shouldn't reach here > + * as the timer base wouldn't be idle. And inline > + * softirq processing after a call to local_bh_enable() > + * within idle loop sound too fun to be considered here. > + */ > + if (in_serving_softirq()) > + return; > + > + WARN_ON_ONCE("Late timer enqueue may be ignored\n"); > +#endif > +} > + > /* > * When add_timer_on() enqueues a timer into the timer wheel of an > * idle CPU then this timer might expire before the next timer event > @@ -688,8 +708,10 @@ static void wake_up_idle_cpu(int cpu) > { > struct rq *rq = cpu_rq(cpu); > > - if (cpu == smp_processor_id()) > + if (cpu == smp_processor_id()) { > + wake_idle_assert_possible(); > return; > + } > > if (set_nr_and_not_polling(rq->idle)) > smp_send_reschedule(cpu);