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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 autolearn=no 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 BB5C0C55186 for ; Thu, 23 Apr 2020 13:44:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 92BE720781 for ; Thu, 23 Apr 2020 13:44:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728608AbgDWNoI (ORCPT ); Thu, 23 Apr 2020 09:44:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:36646 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728133AbgDWNoH (ORCPT ); Thu, 23 Apr 2020 09:44:07 -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 5D8402077D; Thu, 23 Apr 2020 13:44:06 +0000 (UTC) Date: Thu, 23 Apr 2020 09:44:03 -0400 From: Steven Rostedt To: Peter Zijlstra Cc: Hillf Danton , Mike Galbraith , lkml , Ingo Molnar Subject: Re: [PATCH] sched: make p->prio independent of p->mm Message-ID: <20200423094403.6f1d2b8d@gandalf.local.home> In-Reply-To: <20200423092620.GR20730@hirez.programming.kicks-ass.net> References: <20200423040128.6120-1-hdanton@sina.com> <20200423092620.GR20730@hirez.programming.kicks-ass.net> 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 Thu, 23 Apr 2020 11:26:20 +0200 Peter Zijlstra wrote: > On Thu, Apr 23, 2020 at 12:01:28PM +0800, Hillf Danton wrote: > > --- a/kernel/sched/core.c > > +++ b/kernel/sched/core.c > > @@ -4796,13 +4796,19 @@ recheck: > > return -EINVAL; > > > > /* > > - * Valid priorities for SCHED_FIFO and SCHED_RR are > > - * 1..MAX_USER_RT_PRIO-1, valid priority for SCHED_NORMAL, > > - * SCHED_BATCH and SCHED_IDLE is 0. > > + * The MAX_USER_RT_PRIO value allows the actual maximum > > + * RT priority to be separate from the value exported to > > + * user-space. This allows kernel threads to set their > > + * priority to a value higher than any user task. > > */ > > - if ((p->mm && attr->sched_priority > MAX_USER_RT_PRIO-1) || > > - (!p->mm && attr->sched_priority > MAX_RT_PRIO-1)) > > - return -EINVAL; > > + if (p->flags & PF_KTHREAD) { > > + if (attr->sched_priority > MAX_RT_PRIO - 1) > > + return -EINVAL; > > + } else { > > + if (attr->sched_priority > MAX_USER_RT_PRIO - 1) > > + return -EINVAL; > > + } > > + > > Arguably we can do away with the check entirely, MAX_RT_PRIO == > MAX_USER_RT_PRIO. Heh, that was one of my first patches accepted in the mainline kernel! :-) And the reason we added it, was because there was a small time when the RT patch (or my variation of it) had MAX_USER_RT_PRIO and MAX_RT_PRIO different values, and would crash in that case here. d46523ea32a79 ("fix MAX_USER_RT_PRIO and MAX_RT_PRIO") I would say if we get rid of that check, get rid of the MAX_USER_RT_PRIO with it, and make everything use MAX_RT_PRIO. -- Steve