[PATCH 3/3] tasklet: Introduce new initialization API

[Matthew Wilcox]

On Wed, Jul 15, 2020 at 08:08:47PM -0700, Kees Cook wrote:
> +#define DECLARE_TASKLET(name, _callback)		\
> +struct tasklet_struct name = {				\
> +	.count = ATOMIC_INIT(0),			\
> +	.callback = _callback,				\
> +	.use_callback = true,				\
> +}
> +
> +#define DECLARE_TASKLET_DISABLED(name, _callback)	\
> +struct tasklet_struct name = {				\
> +	.count = ATOMIC_INIT(1),			\
> +	.callback = _callback,				\
> +}

You forgot to set use_callback here.

> @@ -547,7 +547,10 @@ static void tasklet_action_common(struct softirq_action *a,
>  				if (!test_and_clear_bit(TASKLET_STATE_SCHED,
>  							&t->state))
>  					BUG();
> -				t->func(t->data);
> +				if (t->use_callback)
> +					t->callback(t);
> +				else
> +					t->func(t->data);

I think this is the wrong way to do the conversion.  Start out by setting
t->data to (unsigned long)t in the new initialisers.  Then convert the
drivers (all 350 of them) to the new API.  Then you can get rid of 'data'
from the tasklet_struct.