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

Matt Mackall
2005-01-11T02:36:00Z

On Sat, Jan 08, 2005 at 12:12:59AM -0600, Jack O'Quin wrote:
> Chris Wright <chrisw@osdl.org> writes:
>
> > * Christoph Hellwig (hch@infradead.org) wrote:
> >> So to make forward progress I'd like the audio people to confirm whether
> >> the mlock bits in 2.6.9+ do help that half of their requirement first
> >
> > It sure should, but I guess they can reply on that.
>
> That does seem to work now (finally). It looks like that longstanding
> CAP_IPC_LOCK bug is finally fixed, too.
>
> I find it hard to understand why some of you think PAM is an adequate
> solution.

The best we can do _here_ is present something that userspace can use
sensibly. We can't make userspace actually use it that way though.

Rlimits are neither UID/GID or PAM-specific. They fit well within
the general model of UNIX security, extending an existing mechanism
rather than adding a completely new one. That PAM happens to be the
way rlimits are usually administered may be unfortunate, yes, but it
doesn't mean that rlimits is the wrong way.

> Running `nice --20' is still significantly worse than SCHED_FIFO, but
> not the unmitigated disaster shown in the middle column. But, this
> improved performance is still not adequate for audio work. The worst
> delay was absurdly long (~1/2 sec).

Let's work on that. It'd be _far_ better to have unprivileged near-RT
capability everywhere without potential scheduling DoS.

--
Mathematics is the supreme nostalgia of our time.