Re: serial flow control appears broken

Maciej W. Rozycki
2007-07-30T09:45:31Z

On Sat, 28 Jul 2007, Russell King wrote:

> Essentially, any complex interrupt handler (such as an IDE interrupt
> doing a multi-sector PIO transfer _in interrupt context_) can cause this
> kind of starvation. That's why Linux 1.x had bottom halves - so that
> the time consuming work could be moved out of the interrupt handler,
> thereby causing minimal the blockage of other interrupts.
>
> Unfortunately, that kind of design has been long since forgotten.
> Apparantly modern machines are fast enough that it doesn't have to be
> worried about anymore... Or are they?

I would guess it is not that the machines are fast enough, but that this
two-level processing makes things more complicated. Enough that most
people would not bother digging into it unless really forced. Only
occasional latency problems are probably not enough of a force.

Maciej