Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752907AbbBWRdS (ORCPT ); Mon, 23 Feb 2015 12:33:18 -0500 Received: from mail-qa0-f44.google.com ([209.85.216.44]:55352 "EHLO mail-qa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752186AbbBWRdR (ORCPT ); Mon, 23 Feb 2015 12:33:17 -0500 Date: Mon, 23 Feb 2015 12:33:13 -0500 (EST) From: Nicolas Pitre To: Peter Zijlstra cc: linux-kernel@vger.kernel.org, mingo@kernel.org, rjw@rjwysocki.net, tglx@linutronix.de, Preeti U Murthy Subject: Re: [PATCH 32/35] clockevents: Fix cpu down race for hrtimer based broadcasting In-Reply-To: Message-ID: References: <20150216121435.203983131@infradead.org> <20150216122413.880378334@infradead.org> <20150221124659.GG23367@worktop.ger.corp.intel.com> <20150223161457.GA5029@twins.programming.kicks-ass.net> User-Agent: Alpine 2.11 (LFD 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1234 Lines: 35 On Mon, 23 Feb 2015, Nicolas Pitre wrote: > On Mon, 23 Feb 2015, Peter Zijlstra wrote: > > > The reported function that fails: bL_switcher_restore_cpus() is called > > in the error paths of the former and the main path in the latter to make > > the 'stolen' cpus re-appear. > > > > The patch in question somehow makes that go boom. > > > > > > Now what all do you need to do to make it go boom? Just enable/disable > > the switcher once and it'll explode? Or does it need to do actual > > switches while it is enabled? > > It gets automatically enabled during boot. Then several switches are > performed while user space is brought up. If I manually disable it > via /sys then it goes boom. OK. Forget the bL switcher. I configured it out of my kernel and then managed to get the same crash by simply hotplugging out one CPU and plugging it back in. $ echo 0 > /sys/devices/system/cpu/cpu2/online [CPU2 gone] $ echo 1 > /sys/devices/system/cpu/cpu2/online [Boom!] Nicolas -- 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/