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Re: time taken by ISR?

On Thu, Oct 05, 2000 at 11:18:51PM -0700, honne gowda gowda wrote:
> hi,
> i am writting device driver for ad1674(adc) based card. here the card
> supports timer triggerred and interrupt driven data transfer and other modes
> of transfer.the conversion rate of adc chip is 10 micro secs, that means i
> can do sampling at the rate of 100K.
> after every conversion the adc raises an interrupt.
> my question is: what is the amount of time taken by the(in worst case)
> interrupt handler to get executed.

Short answer: Linux has no upper bound on the interrupt latency.

Long answer: See some of the recent threads on the exchanges between 
Linus Torvalds and the people who wanted to make Linux a good OS for
multimedia recording/editing. They wanted to introduce code into Linux
kernel at "strategic" points where it would check for pending events
that needed attention in "real time".

I don't know what happened to the code - it probably didn't make it.

Also, Linux has no concept of interrupt "levels". Either all interrupts
are blocked or none.