Interrupt handling

[Darshan Ghumare]

Sir,

On Tue, Feb 15, 2011 at 4:16 PM, Mulyadi Santosa
<mulyadi.santosa at gmail.com>wrote:

> Hi... :)
>
> On Tue, Feb 15, 2011 at 16:08, Darshan Ghumare
> <darshan.ghumare at gmail.com> wrote:
> > Sir,
> > On x86 UP (Single CPU), Can lower priority (say) IRQ5 preempt higher one
> > (say) IRQ4 (Currently, CPU is executing interrupt handler of IRQ4)?
>
> In Linux kernel, I never heard such irq prioritizing. Linux kernel
> does general preemption such that any code path could preempt other
> code path as long as preemption is allowed at that point and/or
> interrupt is enabled (which one affect the situation depends on type
> of code path).
>

IMHO, When the Processor is executing interrupt handler of IRQ4 then
Processor is the one which pushes SS, SP, EFLAGS, CS  & EIP  on stack (in
this case this will all corresponds to interrupt handler of IRQ4) & loads CS
& EIP corresponding to IRQ5.
So, how come its depends on OS (kernel)? Please correct me if I am wrong.


> But, vaguely I read that Windows kernel does that.... that's why in
> certain BSOD you read message prefixed with "IRQL xxx xxx xxxx". That
> means lower interrupt handler somehow preempt higher one and that's
> not allowed.
>
> It comes from my raw observation so things might be wrong somewhere...
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
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