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 <stable@xxxxxxxxxxxxxxx> know about it.
>From 907565337ebf998a68cb5c5b2174ce5e5da065eb Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Date: Thu, 3 Nov 2016 10:29:28 -0600
Subject: Fix: Disable sys_membarrier when nohz_full is enabled
From: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
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 <mathieu.desnoyers@xxxxxxxxxxxx>
CC: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Acked-by: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/membarrier.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/kernel/membarrier.c
+++ b/kernel/membarrier.c
@@ -16,6 +16,7 @@
#include <linux/syscalls.h>
#include <linux/membarrier.h>
+#include <linux/tick.h>
/*
* 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@xxxxxxxxxxxx are
queue-4.10/fix-disable-sys_membarrier-when-nohz_full-is-enabled.patch