Subject: Re: Proposal for generalized MI soft interrupts
To: None <firstname.lastname@example.org>
From: Gordon W. Ross <email@example.com>
Date: 01/30/1997 11:26:31
> Date: Thu, 30 Jan 1997 10:05:44 -0500
> From: Bill Sommerfeld <firstname.lastname@example.org>
> 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?
> - Bill
Solaris has a similar "softintr" facility:
void ddi_remove_softintr(ddi_softintr_t id);
void ddi_trigger_softintr(ddi_softintr_t id);
Their interface specifies that the function called as a result
of ddi_trigger_softintr() is called at low priority (something
corresponding to our splsoft).
I suggest we include in the following in interface specification:
Soft interrupt functions attached with the levels listed below are
called at the interrupt priority shown to the right:
IPL_SOFTSERIAL spltty() *
* not sure what that last one should be.
Anyway, the point is that we should fully specify the calling
environment for the functions attached.
Another question one might ask is: Can the attached function
possibly be called more often than the number of times one
calls softintr_request(cookie) with its cookie? It simplifies
some MD implementations somewhat if that can be allowed.