[EMAIL PROTECTED] writes:
> On Thu, Jun 29, 2000 at 04:39:18PM -0600, Richard Gooch wrote:
> > I'd still prefer the scheme I suggested a while back: run Linux
> > processes on the RT scheduler if they have RT priority, and switch
> > between RT and Linux scheduler whenever going between user-space and
> > kernel-space.
> >
> > This would mean you get complete access to all system calls and user
> > libraries within a RT process, without having to bloat the kernel with
> > a pile of pseudo-RT hacks.
> >
> > It would also mean we could consider ripping out SCHED_FIFO and
> > SCHED_RR from the Linux scheduler, hence simplifying it.
> >
> > Somebody please find the time to implement this :-)
>
> I came back from Australia, all pumped up to do this, proposed it to
> the RTLinux list and got hammered by RTAI proponents who wanted to
> point out that LXRT did something like this already. The more I
> thought about that something, the more happy I got that they would
> be hacking away trying to fix it instead of me -- and I also
> couldn't get comfortable with the memory management unit trickery
> that would be needed for either scheme.
I don't see why the MM stuff is an issue: just tap in at every place
where we do a user<->kernel transition. There's not that many, after
all.
So if a hard-RT user-space process suddenly takes a page fault, the
CPU switches to kernel mode (still running under the RTLinux
scheduler), and the first thing we do is call rtl_drop_rt(). Same for
all other kernel entry points.
Regards,
Richard....
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