Re: Interrupt handlers and mutex

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> (2) What happens when the interrupt handler cannot acquire the
>> mutex?  Will the LWP that holds it ever be able to run again?
> That can't happen.  The cpu will spin until the mutex is acquired.

How can it ever be acquired?  As long as the CPU sits spinning in the
interrupt handler nothing but higher-priority interrupt handlers will
get a chance to run, so the thread holding it can never finish its job
and release it.

Sure, if it's an MP system and the holding thread is on another CPU, I
can see it, but I can't see how that can be guaranteed to be the case.

There's clearly something I'm missing here.  What is it?

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