Re: Preempt & how long it takes to interrupt (was Re: [2.4.17/18pre] VM and swap - it's really unusable)

Robert Love
2002-01-20T20:18:37Z

On Fri, 2002-01-18 at 17:41, Pavel Machek wrote:

> So... how long do you have to stay in interrupt for it to be a bug?
>
> There's *no* requirement that says "it may not take second to handle
> an interrupt". Actually I guess that some nasty conditions (UHCI needs
> reset?) may take that long in interrupt. Oh and actually few releases
> ago, console switching was done from interrupt and it *did* take 2
> seconds for me.
>
> If someone assumes interrupts are "short", he has broken code already.

Agreed. Conversely, however, writing code that introduces long
interrupt-off periods should be considered a BUG.

In other words, relying on short interrupt-off periods is bad form, but
so is writing gross code that rudely keeps them off.

I think we all considered the long off periods in VT switching and fbdev
a bug.

Robert Love