From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:49350 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751643AbcKLR6Z (ORCPT ); Sat, 12 Nov 2016 12:58:25 -0500 Received: from pps.filterd (m0098399.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.17/8.16.0.17) with SMTP id uACHsWuh077770 for ; Sat, 12 Nov 2016 12:58:24 -0500 Received: from e34.co.us.ibm.com (e34.co.us.ibm.com [32.97.110.152]) by mx0a-001b2d01.pphosted.com with ESMTP id 26p045gxh3-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Sat, 12 Nov 2016 12:58:24 -0500 Received: from localhost by e34.co.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Sat, 12 Nov 2016 10:58:23 -0700 Date: Sat, 12 Nov 2016 09:58:20 -0800 From: "Paul E. McKenney" To: Mathieu Desnoyers Cc: linux-kernel , Josh Triplett , rostedt , Lai Jiangshan , stable Subject: Re: [PATCH] Fix: disable sys_membarrier when nohz_full is enabled Reply-To: paulmck@linux.vnet.ibm.com References: <1478190568-5829-1-git-send-email-mathieu.desnoyers@efficios.com> <20161103174911.GL3716@linux.vnet.ibm.com> <656710430.17218.1478538539895.JavaMail.zimbra@efficios.com> <20161107180614.GR24166@linux.vnet.ibm.com> <1462452244.17824.1478542214440.JavaMail.zimbra@efficios.com> <20161107200315.GA3438@linux.vnet.ibm.com> <26153082.18614.1478603751607.JavaMail.zimbra@efficios.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <26153082.18614.1478603751607.JavaMail.zimbra@efficios.com> Message-Id: <20161112175820.GV4127@linux.vnet.ibm.com> Sender: stable-owner@vger.kernel.org List-ID: On Tue, Nov 08, 2016 at 11:15:51AM +0000, Mathieu Desnoyers wrote: > ----- On Nov 7, 2016, at 3:03 PM, Paul E. McKenney paulmck@linux.vnet.ibm.com wrote: > > > On Mon, Nov 07, 2016 at 06:10:14PM +0000, Mathieu Desnoyers wrote: > >> > >> ----- On Nov 7, 2016, at 1:06 PM, Paul E. McKenney paulmck@linux.vnet.ibm.com > >> wrote: > >> > >> > On Mon, Nov 07, 2016 at 05:08:59PM +0000, Mathieu Desnoyers wrote: > >> >> ----- On Nov 3, 2016, at 1:49 PM, Paul E. McKenney paulmck@linux.vnet.ibm.com > >> >> wrote: > >> >> > >> >> > On Thu, Nov 03, 2016 at 10:29:28AM -0600, Mathieu Desnoyers wrote: > >> >> >> Userspace applications should be allowed to expect the membarrier system > >> >> >> call with MEMBARRIER_CMD_SHARED command to issue memory barriers on > >> >> >> nohz_full CPUs, but synchronize_sched() does not take those into > >> >> >> account. > >> >> >> > >> >> >> Given that we do not want unrelated processes to be able to affect > >> >> >> real-time sensitive nohz_full CPUs, simply return ENOSYS when membarrier > >> >> >> is invoked on a kernel with enabled nohz_full CPUs. > >> >> >> > >> >> >> Signed-off-by: Mathieu Desnoyers > >> >> >> CC: "Paul E. McKenney" > >> >> > > >> >> > Acked-by: "Paul E. McKenney" > >> >> > >> >> Hi Paul, > >> >> > >> >> Do you plan to pick it up through your tree, or I should sent > >> >> it directly to Linus ? > >> > > >> > Your choice. I believe that the original went some other way, but I > >> > would be fine carrying this one. > >> > >> Not sure what you mean by "the original" ? And which other way ? > >> I have not been notified about this. > > > > If I remember correctly, you sent the original sys_membarrier() > > patch through akpm or similar. > > Ah right, the original implementation, yes. > > > > >> If you can carry this patch it would be very much appreciated, > > > > Will do! > > Especially since the regression is somewhat related to RCU > behavior wrt nohz_full, getting it through your tree seems > relevant. I have it queued for 4.11, thank you! Thanx, Paul