Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933788Ab3GENv6 (ORCPT ); Fri, 5 Jul 2013 09:51:58 -0400 Received: from www.linutronix.de ([62.245.132.108]:45392 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751582Ab3GENv6 (ORCPT ); Fri, 5 Jul 2013 09:51:58 -0400 Date: Fri, 5 Jul 2013 15:51:57 +0200 (CEST) From: Thomas Gleixner To: David Vrabel cc: Ingo Molnar , "H. Peter Anvin" , LKML , konrad.wilk@oracle.com, john.stultz@linaro.org, xen-devel@lists.xen.org, Artem Savkov Subject: Re: [tip:timers/core] hrtimers: Support resuming with two or more CPUs online (but stopped) In-Reply-To: <51D6CE19.1050503@citrix.com> Message-ID: References: <1372329348-20841-2-git-send-email-david.vrabel@citrix.com> <20130705093003.GA4033@cpv436-motbuntu> <51D69ACF.9020001@citrix.com> <51D6CE19.1050503@citrix.com> User-Agent: Alpine 2.02 (DEB 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,URIBL_BLOCKED=0.001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1441 Lines: 38 On Fri, 5 Jul 2013, David Vrabel wrote: > On 05/07/13 11:25, Thomas Gleixner wrote: > > On Fri, 5 Jul 2013, David Vrabel wrote: > > > > You failed to CC Artem :( > > > >> On 05/07/13 10:30, Artem Savkov wrote: > >>> This commit brings up a warning about a potential deadlock in > >>> smp_call_function_many() discussed previously: > >>> https://lkml.org/lkml/2013/4/18/546 > >> > >> Can we just avoid the wait in clock_was_set()? Something like this? > >> > >> 8<------------------------------------------------------ > >> hrtimers: do not wait for other CPUs in clock_was_set() > >> > >> Calling on_each_cpu() and waiting in a softirq causes a WARNing about > >> a potential deadlock. > >> > >> Because hrtimers are per-CPU, it is sufficient to ensure that all > >> other CPUs' timers are reprogrammed as soon as possible and before the > >> next softirq on that CPU. There is no need to wait for this to be > >> complete on all CPUs. > > Unfortunately this doesn't look sufficient. on_each_cpu(..., 0) may > still wait for other calls to complete before queuing the calls due to > the use of a single set of per-CPU csd data. Hrmpf. I'll fix it in the non elegant way :( 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/