From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753252AbeCPKMi (ORCPT ); Fri, 16 Mar 2018 06:12:38 -0400 Received: from merlin.infradead.org ([205.233.59.134]:38332 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751644AbeCPKLa (ORCPT ); Fri, 16 Mar 2018 06:11:30 -0400 Date: Fri, 16 Mar 2018 11:11:24 +0100 From: Peter Zijlstra To: Alexey Brodkin Cc: "linux-arch@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "Vineet.Gupta1@synopsys.com" , "linux-snps-arc@lists.infradead.org" Subject: Re: Do we need to disable preemption in flush_tlb_range()? Message-ID: <20180316101124.GB4064@hirez.programming.kicks-ass.net> References: <1519917189.13866.6.camel@synopsys.com> <5a5c67c1-9f45-f908-2c8d-0914cd616a18@synopsys.com> <20180315082720.GT4064@hirez.programming.kicks-ass.net> <1521106770.11552.70.camel@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1521106770.11552.70.camel@synopsys.com> User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 15, 2018 at 09:39:31AM +0000, Alexey Brodkin wrote: > Hi Peter, > > On Thu, 2018-03-15 at 09:27 +0100, Peter Zijlstra wrote: > > On Wed, Mar 14, 2018 at 01:19:01PM -0700, Vineet Gupta wrote: > > > +CC Peter since we have his attention ;-) > > > > Yeah, timezone collision there, I typically sleep at 1am ;-) > > > > > On 03/01/2018 07:13 AM, Alexey Brodkin wrote: > > > > Hi Vineet, > > > > > > > > Just noticed that in comments for smp_call_function_many() it is said that > > > > preemption must be disabled during its execution. And that function gets executed > > > > among other ways like that: > > > > -------------------------->8----------------------- > > > > flush_tlb_range() > > > > -> on_each_cpu_mask() > > > > -> smp_call_function_many() > > > > -------------------------->8----------------------- > > > > > > In general I prefer not to - Peter what say you ? > > > > The comment with smp_call_function_many() is correct, it relies on > > preemption being disabled in a number of ways. I would expect > > this_cpu_ptr() for example to complain when used with preemption > > enabled (CONFIG_DEBUG_PREEMPT). So on_each_cpu_mask() already disables preemption around calling smp_call_function_many().