From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755338AbcJUMFt (ORCPT ); Fri, 21 Oct 2016 08:05:49 -0400 Received: from merlin.infradead.org ([205.233.59.134]:45296 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754148AbcJUMFq (ORCPT ); Fri, 21 Oct 2016 08:05:46 -0400 Date: Fri, 21 Oct 2016 14:05:36 +0200 From: Peter Zijlstra To: Christian Borntraeger Cc: Nicholas Piggin , linux-kernel@vger.kernel.org, linux-s390 , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Heiko Carstens , Martin Schwidefsky , Noam Camus , virtualization@lists.linux-foundation.org, xen-devel-request@lists.xenproject.org, kvm@vger.kernel.org Subject: Re: [PATCH 2/5] stop_machine: yield CPU during stop machine Message-ID: <20161021120536.GC3142@twins.programming.kicks-ass.net> References: <1477051138-1610-1-git-send-email-borntraeger@de.ibm.com> <1477051138-1610-3-git-send-email-borntraeger@de.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1477051138-1610-3-git-send-email-borntraeger@de.ibm.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 21, 2016 at 01:58:55PM +0200, Christian Borntraeger wrote: > stop_machine can take a very long time if the hypervisor does > overcommitment for guest CPUs. When waiting for "the one", lets > give up our CPU by using the new cpu_relax_yield. This seems something that would apply to most other virt stuff. Lets Cc a few more lists for that. > Signed-off-by: Christian Borntraeger > --- > kernel/stop_machine.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c > index ec9ab2f..1eb8266 100644 > --- a/kernel/stop_machine.c > +++ b/kernel/stop_machine.c > @@ -194,7 +194,7 @@ static int multi_cpu_stop(void *data) > /* Simple state machine */ > do { > /* Chill out and ensure we re-read multi_stop_state. */ > - cpu_relax(); > + cpu_relax_yield(); > if (msdata->state != curstate) { > curstate = msdata->state; > switch (curstate) { > -- > 2.5.5 >