Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759625Ab3EOQ7a (ORCPT ); Wed, 15 May 2013 12:59:30 -0400 Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:54727 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759374Ab3EOQ73 (ORCPT ); Wed, 15 May 2013 12:59:29 -0400 Date: Wed, 15 May 2013 18:59:15 +0200 From: Peter Zijlstra To: Steven Rostedt Cc: Don Zickus , Frederic Weisbecker , Ingo Molnar , LKML , "Paul E. McKenney" , Andrew Morton , Thomas Gleixner , "H. Peter Anvin" Subject: Re: [PATCH 1/2] nohz: Disable LOCKUP_DETECTOR when NO_HZ_FULL is enabled Message-ID: <20130515165915.GE13916@laptop.home> References: <1368547372-21011-1-git-send-email-fweisbec@gmail.com> <1368547372-21011-2-git-send-email-fweisbec@gmail.com> <20130515083729.GC10510@laptop.programming.kicks-ass.net> <20130515150652.GP23604@redhat.com> <1368631622.6828.69.camel@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1368631622.6828.69.camel@gandalf.local.home> 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 Content-Length: 1045 Lines: 24 On Wed, May 15, 2013 at 11:27:02AM -0400, Steven Rostedt wrote: > Right now perf requires a tick, not sure exactly why, but you can look > at the code in perf_event_task_tick(). Thus if NO_HZ_FULL sees that a > perf tick is pending, it won't disable ticks. Unfortunately, the > watchdogs, both NMI and soft lockup, use the perf infrastructure to > trigger NMIs or interrupts. This adds a perf element on the rotate list > and keeps NO_HZ_FULL from *ever* activating. > Hmm.. Stephane had a bunch of patches converting the rotation thing to an hrtimer. I seem to have forgotten what happened to them but I can't seem to find them merged. I'll go look. That leaves the frequency stuff, but the watchdog doesn't use that. At which point we could run the watchdog without perf_event_task_tick(). > -- 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/