On Sun, Dec 11, 2011 at 1:12 PM, Andriy Gapon <a...@freebsd.org> wrote:
>
> Does the following change do what I think that it does?
> Thank you!
>
> Author: Andriy Gapon <a...@icyb.net.ua>
> Date:   Thu Sep 1 16:50:13 2011 +0300
>
>    ukbd: drop local duplicate of kern_yield and use that instead
>
> diff --git a/sys/dev/usb/input/ukbd.c b/sys/dev/usb/input/ukbd.c
> index 086c178..8078cbb 100644
> --- a/sys/dev/usb/input/ukbd.c
> +++ b/sys/dev/usb/input/ukbd.c
> @@ -399,33 +399,6 @@ ukbd_put_key(struct ukbd_softc *sc, uint32_t key)
>  }
>
>  static void
> -ukbd_yield(void)
> -{
> -       struct thread *td = curthread;
> -       uint32_t old_prio;
> -
> -       DROP_GIANT();
> -
> -       thread_lock(td);
> -
> -       /* get current priority */
> -       old_prio = td->td_base_pri;
> -
> -       /* set new priority */
> -       sched_prio(td, td->td_user_pri);
> -
> -       /* cause a task switch */
> -       mi_switch(SW_INVOL | SWT_RELINQUISH, NULL);
> -
> -       /* restore priority */
> -       sched_prio(td, old_prio);
> -
> -       thread_unlock(td);
> -
> -       PICKUP_GIANT();
> -}
> -
> -static void
>  ukbd_do_poll(struct ukbd_softc *sc, uint8_t wait)
>  {
>
> @@ -439,7 +412,7 @@ ukbd_do_poll(struct ukbd_softc *sc, uint8_t wait)
>                while (sc->sc_inputs == 0) {
>
>                        /* give USB threads a chance to run */
> -                       ukbd_yield();
> +                       kern_yield(-1);

Not quite.

1) -1 should be spelled PRI_UNCHANGED, except ukbd_yield() uses
td_user_pri, but then puts it back again, so I think UNCHANGED is what
is meant.
2) kern_yield() calls it a SW_VOL rather than SW_INVOL, which seems
the desired behaviour here anyways, since this is an explicit (i.e.
voluntary) yield.

Thanks,
matthew
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