Re: [PATCH] [request for inclusion] Realtime LSM

Matt Mackall
2005-01-07T20:49:00Z

On Fri, Jan 07, 2005 at 02:27:26PM -0600, Jack O'Quin wrote:
> Matt Mackall <mpm@selenic.com> writes:
>
> > On Thu, Jan 06, 2005 at 11:54:05PM -0600, Jack O'Quin wrote:
> >> Note that sched_setschedule() provides no way to handle the mlock()
> >> requirement, which cannot be done from another process.
> >
> > I'm pretty sure that part can be done by a privileged server handing
> > out mlocked shared memory segments.
>
> If you're "pretty sure", please explain how locking a shared memory
> segment prevents the code and stack of the client's realtime thread
> from page faulting.

You just map your RT-dependent routine (PIC, of course) into the
segment and move your stack pointer into a second segment. I didn't
say it was easy, but it's all just bits. There's also the rlimit
issue.

Or, going the other way, the client app can pass map handles to the
server to bless. Some juggling might be involved but it's obviously
doable.

As has been pointed out, an rlimit solution exists now as well.

--
Mathematics is the supreme nostalgia of our time.