Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755988Ab2FNNc0 (ORCPT ); Thu, 14 Jun 2012 09:32:26 -0400 Received: from www.linutronix.de ([62.245.132.108]:57102 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753073Ab2FNNcZ (ORCPT ); Thu, 14 Jun 2012 09:32:25 -0400 Date: Thu, 14 Jun 2012 15:32:19 +0200 (CEST) From: Thomas Gleixner To: "Paul E. McKenney" cc: LKML , Peter Zijlstra , Ingo Molnar , "Srivatsa S. Bhat" , Rusty Russell , Tejun Heo Subject: Re: [RFC patch 2/5] smpboot: Provide infrastructure for percpu hotplug threads In-Reply-To: <20120614125939.GC2443@linux.vnet.ibm.com> Message-ID: References: <20120613102823.373180763@linutronix.de> <20120613105815.206105518@linutronix.de> <20120613185748.GF2427@linux.vnet.ibm.com> <20120613191745.GG2427@linux.vnet.ibm.com> <20120613204725.GA9858@linux.vnet.ibm.com> <20120614045125.GA30257@linux.vnet.ibm.com> <20120614125939.GC2443@linux.vnet.ibm.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1468 Lines: 40 On Thu, 14 Jun 2012, Paul E. McKenney wrote: > On Thu, Jun 14, 2012 at 01:20:39PM +0200, Thomas Gleixner wrote: > > I gave it a quick shot, but I was not able to reproduce the hang yet. > > Really? I have a strictly Western-Hemisphere bug? ;-) I guess I need to fire up rcu torture to make it surface. > > But looking at the thread function made me look into rcu_yield() and I > > really wonder what kind of drug induced that particular piece of > > horror. > > When you are working on something like RCU priority boosting, no other > drug is in any way necessary. ;-) And how do we protect minors from that ? > > I can't figure out why this yield business is necessary at all. The > > commit logs are as helpful as the missing code comments :) > > > > I suspect that it's some starvation issue. But if we need it, then > > can't we replace it with something sane like the (untested) patch > > below? > > Yep, starvation. I will take a look at your approach after I wake > up a bit more. Btw, if that simpler yield approach is working and I can't see why it shouldn't then you can get rid of the node task as well. The only purpose of it is to push up the priority of yielding tasks, right? Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/