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From:   Pavel Tatashin <pasha.tatashin@oracle.com>
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Subject: [PATCH 4.1 11/65] sched/core: Idle_task_exit() shouldn't use switch_mm_irqs_off()
Date:   Mon,  5 Mar 2018 19:24:44 -0500
Message-Id: <20180306002538.1761-12-pasha.tatashin@oracle.com>
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From: Andy Lutomirski <luto@kernel.org>

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@kernel.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
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@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 18a5348d49afcfc2b95da939143c9420edd78b9e)
Signed-off-by: Pavel Tatashin <pasha.tatashin@oracle.com>
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d253618d09c6..9c905bd94ff0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4979,7 +4979,7 @@ void idle_task_exit(void)
 	BUG_ON(cpu_online(smp_processor_id()));
 
 	if (mm != &init_mm) {
-		switch_mm_irqs_off(mm, &init_mm, current);
+		switch_mm(mm, &init_mm, current);
 		finish_arch_post_lock_switch();
 	}
 	mmdrop(mm);
-- 
2.16.2