[syslinux] CPU usage while at syslinux boot prompt

[Ferenc Wagner]

Geert Stappers <stappers at stappers.nl> writes:

> Op 20081117 om 20:34 schreef Ferenc Wagner:
>> "H. Peter Anvin" <hpa at zytor.com> writes:
>>> I guess I might put a HLT in *as an option* (because people *will*
>>> complain that the serial port loses characters)
>> 
>> I get this very annoying dropout from the Xen hypervisor, and wonder:
>> is this a problem of common serial hardware not supporting interrupt
>> generation or a deeper theoretical one?  Can't you do reliable
>> interrupt driver serial IO on common UARTs by principle? 
>
> That implies setting up the entire interrupt system.
> (FYI: not all the "PCs" have the same interrupt controller,
>  but most the "PCs" have an  i8250 compatible UART)

OK.  But doesn't the BIOS set up such legacy stuff?  As Peter
suggested, SYSLINUX wouldn't need a real serial interrupt handler, a
do-nothing routine would be enough to cancel the HLT.  Isn't it so?
And that would cut most of the busy-waiting.  But I hear that for some
reason this isn't reliable, and I wonder why.
-- 
Cheers,
Feri.