From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [PATCH][RFC] kernel/cpu: do not change the cpus_allowed of the current task when unplugging cpus Date: Mon, 17 Jun 2013 13:49:46 +0200 Message-ID: <51BEF7DA.700@linutronix.de> References: <1368699439-13034-1-git-send-email-chenhui.zhao@freescale.com> <20130607090543.GD10280@linutronix.de> <20130609095942.GA8548@localhost.localdomain> <20130614152917.GA8597@linutronix.de> <20130617104832.GA20410@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, tglx@linutronix.de, leoli@freescale.com, scottwood@freescale.com, Priyanka.Jain@freescale.com To: Zhao Chenhui Return-path: Received: from www.linutronix.de ([62.245.132.108]:34862 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932727Ab3FQLts (ORCPT ); Mon, 17 Jun 2013 07:49:48 -0400 In-Reply-To: <20130617104832.GA20410@localhost.localdomain> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 06/17/2013 12:48 PM, Zhao Chenhui wrote: > I don't think it is necessary to change the mask. migration_call() invoked by > the cpu notify "CPU_DYING" will remove all running tasks from the dying cpu. > Even if the current task is running on the dying cpu, it will be transfered > to another online cpu. I had here hiccups if the task was running on the CPU which should go down. > I guess that changing the mask benefits the latency of the system. > Please correct me. I don't get this. Lets say your system has CPUs 0-15 and you pin your application to CPU0. After this application brings CPU15 down it is allowed to run on CPUs 0-14. This is wrong and has been corrected. The CPU down mechanism should not affected CPU mask of the application. > > -Chenhui > Sebastian