From patchwork Mon Nov 15 23:33:42 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 520107 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1EE46C4321E for ; Mon, 15 Nov 2021 23:36:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0ED3F61B53 for ; Mon, 15 Nov 2021 23:36:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349492AbhKOXjh (ORCPT ); Mon, 15 Nov 2021 18:39:37 -0500 Received: from mail.kernel.org ([198.145.29.99]:43756 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1353456AbhKOXg7 (ORCPT ); Mon, 15 Nov 2021 18:36:59 -0500 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 5640561B60; Mon, 15 Nov 2021 23:34:03 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.95) (envelope-from ) id 1mmlUA-000osx-E4; Mon, 15 Nov 2021 18:34:02 -0500 Message-ID: <20211115233402.293121919@goodmis.org> User-Agent: quilt/0.66 Date: Mon, 15 Nov 2021 18:33:42 -0500 From: Steven Rostedt To: linux-kernel@vger.kernel.org, linux-rt-users Cc: Thomas Gleixner , Carsten Emde , Sebastian Andrzej Siewior , John Kacur , Daniel Wagner , Tom Zanussi , "Srivatsa S. Bhat" , stable-rt@vger.kernel.org Subject: [PATCH RT 3/9] sched: Switch wait_task_inactive to HRTIMER_MODE_REL_HARD References: <20211115233339.509057092@goodmis.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org 5.10.78-rt56-rc1 stable review patch. If anyone has any objections, please let me know. ------------------ From: Sebastian Andrzej Siewior With PREEMPT_RT enabled all hrtimers callbacks will be invoked in softirq mode unless they are explicitly marked as HRTIMER_MODE_HARD. During boot kthread_bind() is used for the creation of per-CPU threads and then hangs in wait_task_inactive() if the ksoftirqd is not yet up and running. The hang disappeared since commit 26c7295be0c5e ("kthread: Do not preempt current task if it is going to call schedule()") but enabling function trace on boot reliably leads to the freeze on boot behaviour again. The timer in wait_task_inactive() can not be directly used by an user interface to abuse it and create a mass wake of several tasks at the same time which would to long sections with disabled interrupts. Therefore it is safe to make the timer HRTIMER_MODE_REL_HARD. Switch the timer to HRTIMER_MODE_REL_HARD. Cc: stable-rt@vger.kernel.org Link: https://lkml.kernel.org/r/20210826170408.vm7rlj7odslshwch@linutronix.de Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) --- kernel/sched/core.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f638d9420553..54fa3bb1b7c4 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2734,7 +2734,7 @@ unsigned long wait_task_inactive(struct task_struct *p, long match_state) ktime_t to = NSEC_PER_SEC / HZ; set_current_state(TASK_UNINTERRUPTIBLE); - schedule_hrtimeout(&to, HRTIMER_MODE_REL); + schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); continue; }