From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S941604AbcKQRTU (ORCPT ); Thu, 17 Nov 2016 12:19:20 -0500 Received: from smtprelay0037.hostedemail.com ([216.40.44.37]:40119 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S934008AbcKQRTS (ORCPT ); Thu, 17 Nov 2016 12:19:18 -0500 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1541:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:2693:2904:3138:3139:3140:3141:3142:3352:3622:3865:3866:3867:3868:3870:3871:3872:3874:4250:5007:6261:7514:7875:7903:8660:10004:10400:10848:10967:11026:11232:11473:11658:11914:12043:12296:12663:12740:12760:13069:13148:13149:13230:13311:13357:13439:14096:14097:14181:14659:14664:14721:21080:21250:30054:30083:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:8,LUA_SUMMARY:none X-HE-Tag: mice35_1f0e7dcdc0644 X-Filterd-Recvd-Size: 2308 Date: Thu, 17 Nov 2016 09:50:11 -0500 From: Steven Rostedt To: Mathieu Desnoyers Cc: "Paul E. McKenney" , Lai Jiangshan , linux-kernel , Josh Triplett , stable Subject: Re: [PATCH] Fix: disable sys_membarrier when nohz_full is enabled Message-ID: <20161117095011.1857bca5@gandalf.local.home> In-Reply-To: <11301812.5114.1479390867218.JavaMail.zimbra@efficios.com> References: <1478190568-5829-1-git-send-email-mathieu.desnoyers@efficios.com> <604945667.4957.1479383194368.JavaMail.zimbra@efficios.com> <20161117134015.GT3612@linux.vnet.ibm.com> <11301812.5114.1479390867218.JavaMail.zimbra@efficios.com> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 17 Nov 2016 13:54:27 +0000 (UTC) Mathieu Desnoyers wrote: > >> > > >> > Acked-by: Lai Jiangshan > >> > > >> > But I'm afraid, in the future, tick_nohz_full will become a default y > >> > feature. thus it makes sys_membarrier() always disabled. we might > >> > need a new MEMBARRIER_CMD_XXX to handle it? > >> > >> This may require that we send an IPI to nohz_full CPUs, which will > >> disturb them real-time wise. Any better ideas ? > > > > Restrict the IPIs to CPUs running the process executing the > > sys_membarrier() system call. This would mean that CPUs only > > are interrupted by their own application's request. > > This would break use-cases of cross-process shared memory. :-( Perhaps make this an opt in. That is, all processes that want to be affected by this can call this function with some flag that sets a flag in tasks struct. And have that process get an IPI even in no-hz-full mode if it asked to do it. -- Steve