X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=kernel%2Fexit.c;h=85a83c831856c193570e40a3b7d3e03ef8862d1c;hb=8d71ff0bef9cf4e70108a9a2762f2361e607abde;hp=16395644a98ff8c060b2f5fd776fe7abadd61c6a;hpb=0b88641f1bafdbd087d5e63987a30cc0eadd63b9;p=firefly-linux-kernel-4.4.55.git

diff --git a/kernel/exit.c b/kernel/exit.c
index 16395644a98f..85a83c831856 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -583,8 +583,6 @@ mm_need_new_owner(struct mm_struct *mm, struct task_struct *p)
 	 * If there are other users of the mm and the owner (us) is exiting
 	 * we need to find a new owner to take on the responsibility.
 	 */
-	if (!mm)
-		return 0;
 	if (atomic_read(&mm->mm_users) <= 1)
 		return 0;
 	if (mm->owner != p)
@@ -627,6 +625,16 @@ retry:
 	} while_each_thread(g, c);
 
 	read_unlock(&tasklist_lock);
+	/*
+	 * We found no owner yet mm_users > 1: this implies that we are
+	 * most likely racing with swapoff (try_to_unuse()) or /proc or
+	 * ptrace or page migration (get_task_mm()).  Mark owner as NULL,
+	 * so that subsystems can understand the callback and take action.
+	 */
+	down_write(&mm->mmap_sem);
+	cgroup_mm_owner_callbacks(mm->owner, NULL);
+	mm->owner = NULL;
+	up_write(&mm->mmap_sem);
 	return;
 
 assign_new_owner: