From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932704AbcKGRIc (ORCPT ); Mon, 7 Nov 2016 12:08:32 -0500 Received: from mail.efficios.com ([167.114.142.141]:59849 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753436AbcKGRIa (ORCPT ); Mon, 7 Nov 2016 12:08:30 -0500 Date: Mon, 7 Nov 2016 17:08:59 +0000 (UTC) From: Mathieu Desnoyers To: "Paul E. McKenney" Cc: linux-kernel , Josh Triplett , rostedt , Lai Jiangshan , stable Message-ID: <656710430.17218.1478538539895.JavaMail.zimbra@efficios.com> In-Reply-To: <20161103174911.GL3716@linux.vnet.ibm.com> References: <1478190568-5829-1-git-send-email-mathieu.desnoyers@efficios.com> <20161103174911.GL3716@linux.vnet.ibm.com> Subject: Re: [PATCH] Fix: disable sys_membarrier when nohz_full is enabled MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [167.114.142.141] X-Mailer: Zimbra 8.7.0_GA_1659 (ZimbraWebClient - FF45 (Linux)/8.7.0_GA_1659) Thread-Topic: disable sys_membarrier when nohz_full is enabled Thread-Index: imKkcUjLnnd88Ryu6h6MzWW2cKiy0g== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- 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 ? Thanks, Mathieu > >> CC: Josh Triplett >> CC: Steven Rostedt >> CC: Lai Jiangshan >> CC: [3.10+] >> --- >> kernel/membarrier.c | 4 ++++ >> 1 file changed, 4 insertions(+) >> >> diff --git a/kernel/membarrier.c b/kernel/membarrier.c >> index 536c727..9f9284f 100644 >> --- a/kernel/membarrier.c >> +++ b/kernel/membarrier.c >> @@ -16,6 +16,7 @@ >> >> #include >> #include >> +#include >> >> /* >> * Bitmask made from a "or" of all commands within enum membarrier_cmd, >> @@ -51,6 +52,9 @@ >> */ >> SYSCALL_DEFINE2(membarrier, int, cmd, int, flags) >> { >> + /* MEMBARRIER_CMD_SHARED is not compatible with nohz_full. */ >> + if (tick_nohz_full_enabled()) >> + return -ENOSYS; >> if (unlikely(flags)) >> return -EINVAL; >> switch (cmd) { >> -- >> 2.1.4 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com