Bill Sommerfeld <sommerfeld@orchard.medford.ma.us> writes:

> 
>    Soft interrupts are used as callbacks for hard interrupts.  Since a
>    soft interrupt is always registered from a hard interrupt routine,
>    it is always blocked at the time it is registered.
> 
> What about cases where one soft interrupt needs to trigger another
> soft interrupt?  For example: when running from IPL_SOFTSERIAL, you
> call the ppp line discipline, and it needs to post an IPL_SOFTNET?

I hadn't thought of that case, but IPL_SOFTSERIAL needs to be `higher'
than IPL_SOFTNET anyway.