Re: interrupt handler

[Richard B. Johnson]

On Fri, 23 Aug 2002, sanket rathi wrote:

> hi,
> Can i use spin lock in the interrupt handler for a singlre processor
> machine. because books says u can not use locks but spin lock is some
> thing diffrent 
> 
> thanks in advance
> 
> --Sanket
> ---------

Interrupts default to OFF within an interrupt handler. Given this,
why would you use a spin-lock within the ISR on a single-processor
machine?

To directly answer your question, YES, you can use a spin-lock
within an ISR even though it won't do anything except add code
on a single processor machine.

On multiple CPU machines, you can use the form of spin-lock that
does not save/restore interrupts within the ISR, and use the
save/restore versions, with the same lock variable, outside the
ISR.

Cheers,
Dick Johnson
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