ipc,sem: remove uneeded sem_undo_list lock usage in exit_sem()

After we acquire the sma->sem_perm lock in exit_sem(), we are protected against a racing IPC_RMID operation. Also at that point, we are the last user of sem_undo_list. Therefore it isn't required that we acquire or use ulp->lock. Signed-off-by: Herton R. Krzesinski <[email protected]> Acked-by: Manfred Spraul <[email protected]> Cc: Davidlohr Bueso <[email protected]> Cc: Rafael Aquini <[email protected]> CC: Aristeu Rozanski <[email protected]> Cc: David Jeffery <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
josf · Aug 14, 2015 · a979558 · a979558
1 parent 602b859
commit a979558
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/ipc/sem.c b/ipc/sem.c
@@ -2123,9 +2123,11 @@ void exit_sem(struct task_struct *tsk)
 		ipc_assert_locked_object(&sma->sem_perm);
 		list_del(&un->list_id);
 
-		spin_lock(&ulp->lock);
+		/* we are the last process using this ulp, acquiring ulp->lock
+		 * isn't required. Besides that, we are also protected against
+		 * IPC_RMID as we hold sma->sem_perm lock now
+		 */
 		list_del_rcu(&un->list_proc);
-		spin_unlock(&ulp->lock);
 
 		/* perform adjustments registered in un */
 		for (i = 0; i < sma->sem_nsems; i++) {