Mail Archives: djgpp/1996/10/18/06:56:59
On Thu, 17 Oct 1996, Charles Sandmann wrote:
>> It'd be necessary to handle only timer and page fault in separate tasks.
>Nope. Think about it a long time, and all the exception situations you can
>end up in (especially with SS/ESP) and you will become convinced that
>all HW interrupts and exceptions need to be tasks if you run at ring 0
>for a robust system. (Hints - what happens if the stack at ESP-4 is
>paged out right before any hardware interrupt? What if ESP is corrupted?)
Right... OTOH, exceptions don't happen that often (only PF possibly does, of
course) so the time penalty wouldn't be that big. And as for HW interrupt
handlers, the multitasker really needs to handle timer only. Timer
interrupt would at times trigger the scheduler which certainly requires
running as a separate task. All the other HW ints that are necessary for the
OS to run would be handled by means call gates and reside in locked memory
area, possibly switching stacks on entry to be 100% sure nothing bad happens..
I guess that's the way Windows work.
>> Maybe it should be designed as a 'shell' running other processes?
>
>This would work - but it could also just be a subroutine library which
>initializes and determines if it's the first one to install the extensions.
I guess thats the trade between size and speed, right?
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