Re: [PATCH 5/7] futex: make futex_parse_waitv() available as a helper

Peter Zijlstra
2023-07-12T09:25:27Z

On Tue, Jul 11, 2023 at 06:47:03PM -0600, Jens Axboe wrote:

> Since we now provide a way to pass in a wake handler and data, ensure we
> use __futex_queue() to avoid having futex_queue() overwrite our wait
> data.

> diff --git a/kernel/futex/waitwake.c b/kernel/futex/waitwake.c
> index 3471af87cb7d..dfd02ca5ecfa 100644
> --- a/kernel/futex/waitwake.c
> +++ b/kernel/futex/waitwake.c
> @@ -446,7 +446,8 @@ static int futex_wait_multiple_setup(struct futex_vector *vs, int count, int *wo
> * next futex. Queue each futex at this moment so hb can
> * be unlocked.
> */
> - futex_queue(q, hb);
> + __futex_queue(q, hb);
> + spin_unlock(&hb->lock);
> continue;
> }

I'm not following; I even applied all your patches up to this point, but
futex_queue() still reads:

static inline void futex_queue(struct futex_q *q, struct futex_hash_bucket *hb)
__releases(&hb->lock)
{
__futex_queue(q, hb);
spin_unlock(&hb->lock);
}

How would it be different and overwrite anything ?!?