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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT 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 AEF62C43219 for ; Fri, 26 Apr 2019 14:13:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7D20D206C1 for ; Fri, 26 Apr 2019 14:13:43 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="C7bZ9Z6F" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726271AbfDZONm (ORCPT ); Fri, 26 Apr 2019 10:13:42 -0400 Received: from merlin.infradead.org ([205.233.59.134]:33906 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726039AbfDZONm (ORCPT ); Fri, 26 Apr 2019 10:13:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=8loiSRaoh42DXeIQjNbiN1USZ8a/MszR2dkFDWexf7M=; b=C7bZ9Z6FeUKzezmLte/+hl18t WPZPTSc/CNVYLtOHh+QwJ9EhnP+5MRcFpeXW/VL/H/IshT0ASW/jIcigeiwlZenHmKkkubIVdfTHd 1PeBE4jgon6yovfndpr2GVv4WeNQwAJnip69qn7vfTrr+2khfzwSdm+furkG8jshuob0pdrEJ7N5/ kpTNq5WFvD+63NZ7DcH0ShNEJmIZarFdWO2V+xTIpByKIqau12/RZKhtwH0YdA57jnXi/x4IilPZ5 vP+CjAlbf54tfy8R0VLDmmiEvADfLtS+cHETma56rZLdZZVovrgJiXGJzlJ21qRrt2Fj6AJxNPy5P d0ugIAUgA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hK1bB-0000qi-CT; Fri, 26 Apr 2019 14:13:09 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id D69DF28B70B85; Fri, 26 Apr 2019 16:13:07 +0200 (CEST) Date: Fri, 26 Apr 2019 16:13:07 +0200 From: Peter Zijlstra To: Phil Auld Cc: Vineeth Remanan Pillai , Nishanth Aravamudan , Julien Desfossez , Tim Chen , mingo@kernel.org, tglx@linutronix.de, pjt@google.com, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, subhra.mazumdar@oracle.com, fweisbec@gmail.com, keescook@chromium.org, kerrnel@google.com, Aaron Lu , Aubrey Li , Valentin Schneider , Mel Gorman , Pawan Gupta , Paolo Bonzini Subject: Re: [RFC PATCH v2 12/17] sched: A quick and dirty cgroup tagging interface Message-ID: <20190426141307.GB2623@hirez.programming.kicks-ass.net> References: <20190425142652.GA979@pauld.bos.csb> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190425142652.GA979@pauld.bos.csb> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 25, 2019 at 10:26:53AM -0400, Phil Auld wrote: > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index e8e5f26db052..b312ea1e28a4 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7541,6 +7541,9 @@ static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype > if (val > 1) > return -ERANGE; > > + if (num_online_cpus() <= 1) > + return -EINVAL; We actually know if there SMT on the system or not, which is much better indication still: if (!static_branch_likely(&sched_smt_present)) return -EINVAL; > if (tg->tagged == !!val) > return 0; > > > > > --