1 files changed, 5 insertions, 0 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index b9d857fe2a5c..be8aa5b98666 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -606,6 +606,11 @@ static void __mmdrop(struct mm_struct *mm)
 
 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);
 }