Re: [PATCH]O18.1int

Con Kolivas
2003-08-25T13:25:30Z

On Mon, 25 Aug 2003 22:49, Måns Rullgård wrote:
> Con Kolivas <kernel@kolivas.org> writes:
> >> >> >> Vanilla test1 has the spin effect. Test2 doesn't. I haven't
> >> >> >> tried vanilla test3 or test4. As I've said, the O16.2-O16.3 patch
> >> >> >> introduced the problem. With that patch reversed, everything is
> >> >> >> fine. What problem does that patch fix?
> >> >> >
> >> >> > It's a generic fix for priority inversion but it induces badness in
> >> >> > smp, and latency in task preemption on up so it's not suitable.
> >> >>
> >> >> Now I'm confused. If that patch is bad, then why is it in O18?
> >> >
> >> > No, the 16.2 patch is bad. 16.3 backed it out.
> >>
> >> OK, but it somehow made XEmacs behave badly.
> >
> > Well it was a generic fix in 16.2 that helped XEmacs as I said. O15
> > also had a generic fix (child not preempting it's parent) but that
> > too was covering up the real issue, but it wasnt as drastic as 16.2.
>
> Of the kernels I've tested, only test1 vanilla and O16.3 and later
> show the problem. Btw, is it related to the XEmacs regexp search
> problem, or is that a different one?

Same thing. Both examples of priority inversion. In your case a parent child
interaction which was worked around in O15. That interaction seems the more
common case.

Con