Commit 2840cf02 authored Sep 19, 2019 by Mathieu Desnoyers Committed by Ingo Molnar Sep 25, 2019

sched/membarrier: Call sync_core only before usermode for same mm



When the prev and next task's mm change, switch_mm() provides the core
serializing guarantees before returning to usermode. The only case
where an explicit core serialization is needed is when the scheduler
keeps the same mm for prev and next.

Suggested-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Kirill Tkhai <tkhai@yandex.ru>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Russell King - ARM Linux admin <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20190919173705.2181-4-mathieu.desnoyers@efficios.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 09554009

include/linux/sched/mm.h

+2 −0

Original line number	Original line	Diff line number	Diff line
	@@ -362,6 +362,8 @@ enum {

	static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)		static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm)
	{		{
			if (current->mm != mm)
			return;
	if (likely(!(atomic_read(&mm->membarrier_state) &		if (likely(!(atomic_read(&mm->membarrier_state) &
	MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))		MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE)))
	return;		return;

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