Re: serial flow control appears broken

[Maciej W. Rozycki]

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
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