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=-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=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 1DD05C433E9 for ; Thu, 11 Mar 2021 12:38:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA49964FFE for ; Thu, 11 Mar 2021 12:38:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233376AbhCKMiF (ORCPT ); Thu, 11 Mar 2021 07:38:05 -0500 Received: from mail.kernel.org ([198.145.29.99]:59878 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233155AbhCKMhb (ORCPT ); Thu, 11 Mar 2021 07:37:31 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 042A964FE7; Thu, 11 Mar 2021 12:37:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1615466251; bh=8ELDtlVQiqEuL1suAV+av1PZS+HMDd8m28xNQesUPg4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=D8SgpFKlTs70Z1OIaiCAJpQO+kVAv0X/ccL4B04KkwdtPZ5WdN5coqwMHcyxZfa3z a72oi9VPWEmfTOoedO0ERZf1T7QUqh4GlVGACE9dQbev53XYWhxbLJ/u7kIse250mx ftMJr9nfnYhXrTw2n1Mw0AisfZtBAoRa9UBStmgsh4O4V4ls4Y5yu3pXNcSeXvbQsI ed5pmSWM0Vt+AtEs6xTnKWg91ytAf0wPmYawfMdYPaqT9otZk83xkSF3nj+TpHyLUL eJc6w1eZBfAq86mBOeO5jriJENM/rWuEFL7uiHQ9pJunedTlMFak0oxddRBlzyzjLw WlnUfzz0jJBfA== From: Frederic Weisbecker To: Peter Zijlstra , Thomas Gleixner Cc: LKML , Frederic Weisbecker , "Rafael J . Wysocki" , Ti Zhou , Yunfeng Ye , "Paul E . McKenney" , Marcelo Tosatti , Ingo Molnar Subject: [PATCH 06/10] timer: Report ignored local enqueue in nohz mode Date: Thu, 11 Mar 2021 13:37:04 +0100 Message-Id: <20210311123708.23501-7-frederic@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210311123708.23501-1-frederic@kernel.org> References: <20210311123708.23501-1-frederic@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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. Reviewed-by: Rafael J. Wysocki Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Paul E. McKenney --- kernel/sched/core.c | 20 +++++++++++++++++++- 1 file changed, 19 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ca2bb629595f..24552911f92b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -674,6 +674,22 @@ int get_nohz_timer_target(void) return cpu; } +/* Make sure the timer won't be ignored in dynticks-idle case */ +static void wake_idle_assert_possible(void) +{ +#ifdef CONFIG_SCHED_DEBUG + /* + * Timers are re-evaluated after idle IRQs. In case of softirq, + * we assume 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. + */ + WARN_ONCE(in_task(), + "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 +704,10 @@ 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); -- 2.25.1