From patchwork Sat Jan 9 02:05:36 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederic Weisbecker X-Patchwork-Id: 360165 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=-19.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 E91AEC43381 for ; Sat, 9 Jan 2021 02:07:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C368523A3C for ; Sat, 9 Jan 2021 02:07:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726820AbhAICHG (ORCPT ); Fri, 8 Jan 2021 21:07:06 -0500 Received: from mail.kernel.org ([198.145.29.99]:41604 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726784AbhAICHF (ORCPT ); Fri, 8 Jan 2021 21:07:05 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id C860623AC4; Sat, 9 Jan 2021 02:05:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1610157959; bh=FruuVTRbSSmFOTUvQqJ2CO8k/I1uHvJl6EZqrve6RFA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=aC10n/IUNawtRE92wVvr68B5rdZLVdR1L9PuWxnwZZX0xx6GiyVTgOYMHLuBy/AgL dx1mlRuQNDmkbd6skznXFvrMqcVdxv0kfgYVHH/W4GJLj3Zqi0cScFpp9CGIqCHzg+ eFeuSiDBn8HzP70aCllSyE+vHIkTBHdLqpGRkAhEXiw/ymu6rwKuYAOJ7pzvx0lcn8 3vou37KCqPlnHItNHWHmf/d4amypl7lWKqrG5B7gKnZtoTC/ulcKka3xfs9CI6FW0m 0YvL0YkudWdWw7wRbSKzRhI2YzhP1j4ooFLaLEeshcP/LSKh8zmsrj1lJiv5gODKpZ PMUB00CHuXEdg== From: Frederic Weisbecker To: Peter Zijlstra , "Paul E . McKenney" Cc: LKML , Frederic Weisbecker , "Rafael J . Wysocki" , Ingo Molnar , Thomas Gleixner , stable@vger.kernel.org Subject: [RFC PATCH 8/8] timer: Report ignored local enqueue in nohz mode Date: Sat, 9 Jan 2021 03:05:36 +0100 Message-Id: <20210109020536.127953-9-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210109020536.127953-1-frederic@kernel.org> References: <20210109020536.127953-1-frederic@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 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. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Paul E. McKenney Cc: 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 6056f0374674..6c8b04272a9a 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -715,6 +715,26 @@ 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 @@ -729,8 +749,10 @@ 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);