From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:57998 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753152AbdCHNMP (ORCPT ); Wed, 8 Mar 2017 08:12:15 -0500 Subject: Patch "Fix: Disable sys_membarrier when nohz_full is enabled" has been added to the 4.10-stable tree To: mathieu.desnoyers@efficios.com, cmetcalf@mellanox.com, fweisbec@gmail.com, gregkh@linuxfoundation.org, jiangshanlai@gmail.com, josh@joshtriplett.org, paulmck@linux.vnet.ibm.com, riel@redhat.com, rostedt@goodmis.org Cc: , From: Date: Wed, 08 Mar 2017 14:11:27 +0100 Message-ID: <14889786874622@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled Fix: Disable sys_membarrier when nohz_full is enabled to the 4.10-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: fix-disable-sys_membarrier-when-nohz_full-is-enabled.patch and it can be found in the queue-4.10 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From 907565337ebf998a68cb5c5b2174ce5e5da065eb Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Thu, 3 Nov 2016 10:29:28 -0600 Subject: Fix: Disable sys_membarrier when nohz_full is enabled From: Mathieu Desnoyers commit 907565337ebf998a68cb5c5b2174ce5e5da065eb upstream. 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: Josh Triplett CC: Steven Rostedt Signed-off-by: Paul E. McKenney Cc: Frederic Weisbecker Cc: Chris Metcalf Cc: Rik van Riel Acked-by: Lai Jiangshan Reviewed-by: Josh Triplett Signed-off-by: Greg Kroah-Hartman --- kernel/membarrier.c | 4 ++++ 1 file changed, 4 insertions(+) --- 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) { Patches currently in stable-queue which might be from mathieu.desnoyers@efficios.com are queue-4.10/fix-disable-sys_membarrier-when-nohz_full-is-enabled.patch