Hi,
There is a small difference in masking and disabling
the interrupt, well both have same effect that
interrupts are note received by CPU, but both have
different scopes.
Masking is done at PIC level by enabling the bit
corresponding to the interrupt line we want to mask.
By masking a particular interrupt line at PIC level,
we make sure that PIC do not forward any interrupt to
CPU received on that line.
As there can be more than one device connected to
single PIC incoming line, so all the devices connected
to masked interrupt line on PIC wont be able to send
their interrupt signals to CPU.
Disabling interrupts is done at CPU level, for intel
CPUs, this is done by "cli" instruction. By doing this
CPU does not respond to any of the interrupts from
outer world.
As far as the "local_irq_disable" is concerned, for
i386, this is a macro defined as follows:
#define local_irq_disable() __asm__
__volatile__("cli": : :"memory")
So you can see here, this macro (on i386) disables the
interrupts, so after this CPU wont respond to
interrupts from outside world unless you again
re-enable them.
cheers !!
--gd
--- tousanjay <tousanjay@xxxxxxxxxxx> wrote:
>
>
> Hi all
> New to the group, just joined...
> I have confursion about interrupt masking/disabling
> What is the difference between masking of interrupts
> and disabling of
> interrupts.
>
> To my understanding when a device interrupts, a
> signal flow from the
> device to the interrupt controller and then from
> intr controller to
> processor. Something like...
> device ---1---> interrupt_controller
> ---2--->processor
> I guess the masking happens at 1 and disabling at 2.
> Is my understanding correct?
> Also when i do local_irq_disable, does it masks the
> interrupt or it
> disables the interrupt.
>
> Thanks and Regards
> Sanjay Kumar
>
>
>
>
>
>
>
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