From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751630AbbIQOk4 (ORCPT ); Thu, 17 Sep 2015 10:40:56 -0400 Received: from casper.infradead.org ([85.118.1.10]:34142 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751026AbbIQOkz (ORCPT ); Thu, 17 Sep 2015 10:40:55 -0400 Date: Thu, 17 Sep 2015 16:35:27 +0200 From: Peter Zijlstra To: Tejun Heo Cc: Paul Turner , Ingo Molnar , Johannes Weiner , lizefan@huawei.com, cgroups , LKML , kernel-team , Linus Torvalds , Andrew Morton Subject: Re: [PATCH 3/3] sched: Implement interface for cgroup unified hierarchy Message-ID: <20150917143527.GJ3604@twins.programming.kicks-ass.net> References: <20150822182916.GE20768@mtj.duckdns.org> <20150824213600.GK28944@mtj.duckdns.org> <20150824221935.GN28944@mtj.duckdns.org> <20150825210234.GE26785@mtj.duckdns.org> <20150912144007.GA8942@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150912144007.GA8942@htj.duckdns.org> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Sep 12, 2015 at 10:40:07AM -0400, Tejun Heo wrote: > So, one of the problems is that the kernel can't have tasks w/o > runnable CPUs, so we have to some workaround when, for whatever > reason, a task ends up with no CPU that it can run on. No, just refuse that configuration. > You say cpuset isn't a layering thing but that simply isn't true. > It's a cgroup-scope CPU mask. It layers atop task affinities > restricting what they can be configured to, limiting the effective > cpumask to the intersection of actually existing CPUs and overriding > individual affinity setting when the intersection doesn't exist. No, just fail. > The kernel does not update all CPU affinity masks when a CPU goes down > or comes up. I'd be happy to fail a CPU down for user tasks where this is the last runnable CPU of.