Posted by Ilya Zakharevich on 01/22/08 00:29

[A complimentary Cc of this posting was sent to
Dave Martindale
<davem@cs.ubc.ca>], who wrote in article <fn2g30$q72$1@swain.cs.ubc.ca>:
> >Do not see any significant difference. The poller would set up a
> >wake-up call, which would generate an interrupt. [And, BTW, why my
> >PCI hardware view shows that USB controllers use interrupts?]
>
> More likely, the poller would set a wakeup call, which would add an
> entry into a timer queue somewhere. The timer interrupts regularly,
> and when the specified time has elapsed, the process that asked for the
> wakeup is scheduled to run again. But it would need to wait for CPU
> resources to do anything. It's unlikely to be called directly from the
> timer interrupt handler.

AFAIK, with any sane OS, a device driver requiring wakeup would not
wait for scheduler. (The scheduler usually has too coarse granularity
- 1msec or above.)

Yours,
Ilya

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