Merge branch 'linus' into locking/core, to pick up fixes and dependencies

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

1 files changed, 12 insertions, 1 deletions

diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h
index 1149533aa2fa..9806184bb3d5 100644
--- a/include/linux/sched/mm.h
+++ b/include/linux/sched/mm.h
@@ -36,7 +36,18 @@ static inline void mmgrab(struct mm_struct *mm)
 	atomic_inc(&mm->mm_count);
 }
 
-extern void mmdrop(struct mm_struct *mm);
+extern void __mmdrop(struct mm_struct *mm);
+
+static inline void mmdrop(struct mm_struct *mm)
+{
+	/*
+	 * The implicit full barrier implied by atomic_dec_and_test() is
+	 * required by the membarrier system call before returning to
+	 * user-space, after storing to rq->curr.
+	 */
+	if (unlikely(atomic_dec_and_test(&mm->mm_count)))
+		__mmdrop(mm);
+}
 
 /**
  * mmget() - Pin the address space associated with a &struct mm_struct.