From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933301AbcKGSSd (ORCPT ); Mon, 7 Nov 2016 13:18:33 -0500 Received: from mail.efficios.com ([167.114.142.141]:60929 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932839AbcKGSS0 (ORCPT ); Mon, 7 Nov 2016 13:18:26 -0500 Date: Mon, 7 Nov 2016 18:10:14 +0000 (UTC) From: Mathieu Desnoyers To: "Paul E. McKenney" Cc: linux-kernel , Josh Triplett , rostedt , Lai Jiangshan , stable Message-ID: <1462452244.17824.1478542214440.JavaMail.zimbra@efficios.com> In-Reply-To: <20161107180614.GR24166@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> 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: SDQdZmTSpQaOYV4V2RbPJelY4PpVGA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- 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 you can carry this patch it would be very much appreciated, Thanks, Mathieu > > Thanx, Paul > >> 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 -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com