From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755667Ab1BNPOf (ORCPT ); Mon, 14 Feb 2011 10:14:35 -0500 Received: from e3.ny.us.ibm.com ([32.97.182.143]:56471 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754222Ab1BNPOe (ORCPT ); Mon, 14 Feb 2011 10:14:34 -0500 Date: Mon, 14 Feb 2011 07:14:02 -0800 From: "Paul E. McKenney" To: Yong Zhang Cc: peterz@infradead.org, linux-kernel@vger.kernel.org Subject: Re: Why does the 2.6.37 scheduler hate RT tasks? Message-ID: <20110214151402.GA2256@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110202011049.GA15084@linux.vnet.ibm.com> <20110214145549.GB2937@zhy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110214145549.GB2937@zhy> User-Agent: Mutt/1.5.20 (2009-06-14) X-Content-Scanned: Fidelis XPS MAILER Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 14, 2011 at 10:55:49PM +0800, Yong Zhang wrote: > On Tue, Feb 01, 2011 at 05:10:49PM -0800, Paul E. McKenney wrote: > > Hello, Peter, > > > > If I create an SCHED_FIFO-priority kthread in pre-2.6.37 kernels, > > things work nicely. If I try in in later kernels, __disable_runtime() > > gets upset occasionally during CPU-hotplug calls when CPUs are inserted. > > If I make the exact same kthreads run SCHED_NORMAL, no problem. > > > > Unfortunately, I need an RT kthread so that I can do priority boosting. > > > > My next thing to try is to demote my kthreads to SCHED_NORMAL at the > > beginning of a CPU-hotplug event and promote them back to SCHED_FIFO at > > the end of the CPU-hotplug event, which would leave the system vulnerable > > to RCU priority inversion during CPU-hotplug events. This would be > > better than the current behavior, but I thought that I should check with > > you to see if there is a better approach. > > Just want to know the status of this issue :) > > Does commit 06c3bc655697b19521901f9254eb0bbb2c67e7e8 cure it? Ah, good to see that this got in! I did extract it from the diagnostic patch that Peter sent out, and it does seem to cure the issue. Thanx, Paul