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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,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 A10F8C0044C for ; Wed, 7 Nov 2018 14:55:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6A1892085B for ; Wed, 7 Nov 2018 14:55:40 +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="DKjg8WYH" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6A1892085B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730995AbeKHA0T (ORCPT ); Wed, 7 Nov 2018 19:26:19 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:48896 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727203AbeKHA0T (ORCPT ); Wed, 7 Nov 2018 19:26:19 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=Km3eX6cyK6wqmqeZh5Hm99t8d322ZtdYDXbuVhfuzdE=; b=DKjg8WYHfR2uZ5JAOjwxui4WE 4rGg5ZUuveYRqHB5TTzLpwQjpBNzTHu3LYythBiDv2q8NC1N226vjMKB+EI9ZIUAjJg66pCv0TyhE 0yE28Xc/BA3fw1ziM7QP4iuR2xcXc7Eyv1T6d9mp/slWqZU5LRFha6SAWxGLdMtldeLIHAEt/czFM AEyFOz3Xc68ha6DaxYdtrpTLym+uoN9l/I7plKEQgJSdx8sisPVUQ5ImNYkF+kzBUcSxIyE17WUnS QVJHjksyfZQx2WfnVAsbndxfK50jVge1BtiIUw5liNj7lGoFpZv6LWNH4E0+P+stZ91xQq/YklQlT ++tH9H7HA==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1gKPEw-0008JB-Eg; Wed, 07 Nov 2018 14:55:30 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id C7DDA20298C0C; Wed, 7 Nov 2018 15:55:27 +0100 (CET) Date: Wed, 7 Nov 2018 15:55:27 +0100 From: Peter Zijlstra To: Patrick Bellasi Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Ingo Molnar , Tejun Heo , "Rafael J . Wysocki" , Vincent Guittot , Viresh Kumar , Paul Turner , Quentin Perret , Dietmar Eggemann , Morten Rasmussen , Juri Lelli , Todd Kjos , Joel Fernandes , Steve Muckle , Suren Baghdasaryan Subject: Re: [PATCH v5 03/15] sched/core: uclamp: map TASK's clamp values into CPU's clamp groups Message-ID: <20181107145527.GI9761@hirez.programming.kicks-ass.net> References: <20181029183311.29175-1-patrick.bellasi@arm.com> <20181029183311.29175-4-patrick.bellasi@arm.com> <20181107133504.GQ9781@hirez.programming.kicks-ass.net> <20181107144809.GH14309@e110439-lin> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181107144809.GH14309@e110439-lin> 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 Wed, Nov 07, 2018 at 02:48:09PM +0000, Patrick Bellasi wrote: > On 07-Nov 14:35, Peter Zijlstra wrote: > You mean se_count overflow ? Yah.. > > And I'm not really a fan of hiding that error in a define like you keep > > doing. > > The #define is not there to mask an overflow, it's there to catch the +#define UCLAMP_MAPERR "clamp value [%u] mapping to clamp group failed\n" Is what I was talking about. > > What's wrong with something like: > > > > if (SCHED_WARN(free_group_id == UCLAMP_GROUPS)) > > return; > > Right, the flow should be: > > 1. try to find a valid clamp group > 2. if you don't find one, the data structures are corrupted > warn once for data corruption > do not map this scheduling entity and return > 3. map the scheduling entity > > Is that ok ? That's what the proposed does. > > and > > > > > + uc_map_new.se_count = uc_map_old.se_count + 1; > > > > if (SCHED_WARN(!new.se_count)) > > new.se_count = -1; > > Mmm... not sure we can recover from a corrupted refcount or an > overflow. > > What should we do on these cases, disable uclamp completely ? You can teach put to never decrement -1 (aka. all 1s). But its all SCHED_DEBUG stuff anyway, so who really cares.