Commit 22299339 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

futex: Remove pointless mmgrap() + mmdrop() 



We always set 'key->private.mm' to 'current->mm', getting an extra
reference on 'current->mm' is quite pointless, because as long as the
task is blocked it isn't going to go away.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
parent 3867913c

kernel/futex.c

+1 −13
Original line number Diff line number Diff line
@@ -331,17 +331,6 @@ static void compat_exit_robust_list(struct task_struct *curr); 
static inline void compat_exit_robust_list(struct task_struct *curr) { }

#endif



static inline void futex_get_mm(union futex_key *key)

{

	mmgrab(key->private.mm);

	/*

	 * Ensure futex_get_mm() implies a full barrier such that

	 * get_futex_key() implies a full barrier. This is relied upon

	 * as smp_mb(); (B), see the ordering comment above.

	 */

	smp_mb__after_atomic();

}



/*

 * Reflects a new waiter being added to the waitqueue.

 */
@@ -432,7 +421,7 @@ static void get_futex_key_refs(union futex_key *key) 
		smp_mb();		/* explicit smp_mb(); (B) */

		break;

	case FUT_OFF_MMSHARED:

		futex_get_mm(key); /* implies smp_mb(); (B) */

		smp_mb();		/* explicit smp_mb(); (B) */

		break;

	default:

		/*
@@ -465,7 +454,6 @@ static void drop_futex_key_refs(union futex_key *key) 
	case FUT_OFF_INODE:

		break;

	case FUT_OFF_MMSHARED:

		mmdrop(key->private.mm);

		break;

	}

}