Date: Thu, 15 Mar 2001 18:25:30 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: arch@FreeBSD.org Subject: Proposal for the CPU interrupt API Message-ID: <XFMail.010315182530.jhb@FreeBSD.org>
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<bikeshed color="green"/
I've got a couple of changes I'd like to make to the rather simple API we have
for maintaining CPU interrupt state. Currently we have this:
void disable_intr(void); - disable interrupts
void enable_intr(void); - enable interrupts
u_int save_intr(void); - get interrupt state
void restore_intr(u_int); - set interrupt state
Typically, interrupts are disabled in the following fashion:
u_int foo = save_intr();
disable_intr();
...
restore_intr(foo);
Unfortunately, this can be somewhat expensive on the Alpha, as both
save_intr() and disable_intr() involve a PAL call. However, the Alpha
returns the previous state whenever you set the interrupt state, which
allows you to only make 1 PAL call. Thus, I'm proposing to change
disable/enable_intr to return the previous state in addition to setting
the state. This then removes the need for save_intr(), and
restore_intr() can stay the same.
Another suggestion I've received is to use intrmask_t as the type
for holding interrupt state rather than u_int.
Finally, another suggestion has been to fudge the names some to stick
all of these functions in one intr_* namespace.
The end result of these changes would be this:
intrmask_t intr_disable(void);
intrmask_t intr_enable(void);
void intr_restore(intrmask_t);
and the code above would become this instead:
intrmask_t foo = intr_disable();
...
intr_restore(foo);
Comments, objections?
/
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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