[PATCH] futex: Invert the return value of lock_pi_update_atomic

[Darren Hart]

Indicate success to the caller by returning 1 for lock acquired.

Signed-off-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx>
---
 kernel/futex.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex.c b/kernel/futex.c
index 391df53..82b96a4 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -1033,7 +1033,7 @@ static int futex_lock_pi_atomic(u32 __user *uaddr,
struct futex_hash_bucket *hb,
 		if (set_waiters)
 			newval |= FUTEX_WAITERS;
 
-		return lock_pi_update_atomic(uaddr, uval, newval);
+		return !lock_pi_update_atomic(uaddr, uval, newval);
 	}
 
 	/*
-- 
2.0.0.rc2




--
Darren

> +       }
>  
>         /*
> -        * We took the lock due to forced take over.
> +        * First waiter. Set the waiters bit before attaching ourself to
> +        * the owner. If owner tries to unlock, it will be forced into
> +        * the kernel and blocked on hb->lock.
>          */
> -       if (unlikely(lock_taken))
> -               return 1;
> -
> +       newval = uval | FUTEX_WAITERS;
> +       ret = lock_pi_update_atomic(uaddr, uval, newval);
> +       if (ret)
> +               return ret;
>         /*
> -        * We dont have the lock. Look up the PI state (or create it if
> -        * we are the first waiter):
> +        * If the update of the user space value succeeded, we try to
> +        * attach to the owner. If that fails, no harm done, we only
> +        * set the FUTEX_WAITERS bit in the user space variable.
>          */
> -       ret = lookup_pi_state(uval, hb, key, ps);
> -
> -       if (unlikely(ret)) {
> -               switch (ret) {
> -               case -ESRCH:
> -                       /*
> -                        * We failed to find an owner for this
> -                        * futex. So we have no pi_state to block
> -                        * on. This can happen in two cases:
> -                        *
> -                        * 1) The owner died
> -                        * 2) A stale FUTEX_WAITERS bit
> -                        *
> -                        * Re-read the futex value.
> -                        */
> -                       if (get_futex_value_locked(&curval, uaddr))
> -                               return -EFAULT;
> -
> -                       /*
> -                        * If the owner died or we have a stale
> -                        * WAITERS bit the owner TID in the user space
> -                        * futex is 0.
> -                        */
> -                       if (!(curval & FUTEX_TID_MASK)) {
> -                               force_take = 1;
> -                               goto retry;
> -                       }
> -               default:
> -                       break;
> -               }
> -       }
> -
> -       return ret;
> +       return attach_to_pi_owner(uval, key, ps);
>  }
>  
>  /**
> @@ -2316,8 +2281,10 @@ retry_private:
>                         goto uaddr_faulted;
>                 case -EAGAIN:
>                         /*
> -                        * Task is exiting and we just wait for the
> -                        * exit to complete.
> +                        * Two reasons for this:
> +                        * - Task is exiting and we just wait for the
> +                        *   exit to complete.
> +                        * - The user space value changed.
>                          */
>                         queue_unlock(hb);
>                         put_futex_key(&q.key);
> 


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