Messages in this thread | | | From | Con Kolivas <> | Subject | Re: [PATCH]O18.1int | Date | Mon, 25 Aug 2003 23:32:25 +1000 |
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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
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