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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_2 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 8648BC55189 for ; Wed, 22 Apr 2020 12:51:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 696C72087E for ; Wed, 22 Apr 2020 12:51:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726848AbgDVMv6 (ORCPT ); Wed, 22 Apr 2020 08:51:58 -0400 Received: from mail.kernel.org ([198.145.29.99]:60372 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726811AbgDVMv6 (ORCPT ); Wed, 22 Apr 2020 08:51:58 -0400 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 9B5BD20787; Wed, 22 Apr 2020 12:51:56 +0000 (UTC) Date: Wed, 22 Apr 2020 08:51:55 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, qais.yousef@arm.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, wim@linux-watchdog.org, Christophe Leroy Subject: Re: [PATCH 16/23] sched,watchdog: Convert to sched_set_fifo() Message-ID: <20200422085155.7549ca94@gandalf.local.home> In-Reply-To: <20200422112832.165197058@infradead.org> References: <20200422112719.826676174@infradead.org> <20200422112832.165197058@infradead.org> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 22 Apr 2020 13:27:35 +0200 Peter Zijlstra wrote: > Because SCHED_FIFO is a broken scheduler model (see previous patches) > take away the priority field, the kernel can't possibly make an > informed decision. > > Effectively changes prio from 99 to 50. Hmm, this being a watchdog, and looking at commit 38a1222ae4f364d ("watchdog: core: make sure the watchdog worker always works") I wonder if we should add a sched_set_high(), or have some other kind of watchdog handler that is guaranteed to trigger. -- Steve > > Cc: wim@linux-watchdog.org > Signed-off-by: Peter Zijlstra (Intel) > Reviewed-by: Ingo Molnar > --- > drivers/watchdog/watchdog_dev.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -1144,14 +1144,13 @@ void watchdog_dev_unregister(struct watc > int __init watchdog_dev_init(void) > { > int err; > - struct sched_param param = {.sched_priority = MAX_RT_PRIO - 1,}; > > watchdog_kworker = kthread_create_worker(0, "watchdogd"); > if (IS_ERR(watchdog_kworker)) { > pr_err("Failed to create watchdog kworker\n"); > return PTR_ERR(watchdog_kworker); > } > - sched_setscheduler(watchdog_kworker->task, SCHED_FIFO, ¶m); > + sched_set_fifo(watchdog_kworker->task); > > err = class_register(&watchdog_class); > if (err < 0) { >