[PATCH 4.9 50/60] sched/core: Idle_task_exit() shouldnt use switch_mm_irqs_off()

From: Greg Kroah-Hartman
Date: Mon Jun 19 2017 - 11:30:43 EST

4.9-stable review patch. If anyone has any objections, please let me know.


From: Andy Lutomirski <luto@xxxxxxxxxx>

commit 252d2a4117bc181b287eeddf848863788da733ae upstream.

idle_task_exit() can be called with IRQs on x86 on and therefore
should use switch_mm(), not switch_mm_irqs_off().

This doesn't seem to cause any problems right now, but it will
confuse my upcoming TLB flush changes. Nonetheless, I think it
should be backported because it's trivial. There won't be any
meaningful performance impact because idle_task_exit() is only
used when offlining a CPU.

Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Fixes: f98db6013c55 ("sched/core: Add switch_mm_irqs_off() and use it in the scheduler")
Link: http://lkml.kernel.org/r/ca3d1a9fa93a0b49f5a8ff729eda3640fb6abdf9.1497034141.git.luto@xxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5469,7 +5469,7 @@ void idle_task_exit(void)

if (mm != &init_mm) {
- switch_mm_irqs_off(mm, &init_mm, current);
+ switch_mm(mm, &init_mm, current);