Re: MSI interrupts

In article <af2d54a7c6c694bf18bcca6e6876a72b@www.novabbs.org>,
MitchAlsup1 <mitchalsup@aol.com> wrote:

On Wed, 19 Mar 2025 14:03:56 +0000, Dan Cross wrote:
>

In article <36b8c18d145cdcd673713b7074cce6c3@www.novabbs.org>,
MitchAlsup1 <mitchalsup@aol.com> wrote:

I want to address the elephant in the room::
>
Why disable interrupts AT ALL !!

>
So that you can have some mechanism for building critical
sections that span multiple instructions, where just having
access to atomics and spin locks isn't enough.

>
You can do this with priority, too.

In the limit, disabling interrupts is just setting the priority
mask to infinity, so in some sense this is de facto true.  But I
don't see how having a prioritization scheme is all that useful.
Consider that when you're starting the system up, you need to
do things like set up an interrupt handler vector, and so on;
surely you want to block all interrupts until you have done so.
If your system model is that receipt of an interrupt may result
in a context switch, and you don't want to do that while holding
a mutex similarly.

Sometimes you really don't want to be interrupted.

- Dan C.