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 <[email protected]> Signed-off-by: Mathieu Desnoyers <[email protected]> Cc: "Paul E. McKenney" <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: "Eric W. Biederman" <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Russell King - ARM Linux admin <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Kirill Tkhai <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> --- include/linux/sched/mm.h | 2 ++ 1 file changed, 2 insertions(+) diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 4a7944078cc3..8557ec664213 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -362,6 +362,8 @@ enum { 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) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE))) return; -- 2.17.1
