On Fri, Feb 11, 2005 at 10:53:27AM +0100, Ingo Molnar wrote: > > * Matt Mackall <[EMAIL PROTECTED]> wrote: > > > On Fri, Feb 11, 2005 at 09:59:42AM +0100, Ingo Molnar wrote: > > > > > > think of SCHED_FIFO on the desktop as an ugly wart, a hammer, that > > > destroys the careful balance of priorities of SCHED_OTHER tasks. Yes, it > > > can be useful if you _need_ a scheduling guarantee due to physical > > > constraints, and it can be useful if the hardware (or the kernel) cannot > > > buffer enough, but otherwise, it only causes problems. > > > > Agreed. I think something short of full SCHED_FIFO will make most > > desktop folks happy. [...] > > ah, but it's not the desktop folks who have to be happy but users :-) > Really, if you ask any app designer then obviously 'the more CPU time we > get for sure, the better our app behaves'. So in that sense SCHED_OTHER > is a fair playground: if you behave nicely you'll have higher priority > and shorter latencies. > > (there are things like SCHED_ISO but how good of a solution they are is > not yet clear.) > > > [...] But a) we still have to figure out exactly how to do that and b) > > we still have to make everyone else happy. The embedded folks (me > > included) would prefer to not run our realtime bits as root too.. > > you dont have to - you can drop root after startup. > > > > but i'm not sure how rlimits will contain the whole problem - can > > > rlimits be restricted to a single app (jackd)? > > > > Yes. There's also the whole soft limit thing. > > i'm curious, how does this 'per-app' rlimit thing work? If a user has > jackd installed and runs it from X unprivileged, how does it get the > elevated rlimit?
It needs a setuid launcher. It would be nice to be able to elevate the rlimits of running processes but the API doesn't exist yet. >From the POV of accidental elevation to RT, soft limits are sufficient. But we can't stop a user from exploiting an app they own with RT privileges from elevating other apps via ptrace+exec or whatever. Nor with RT-LSM. > (while the rest of his desktop still runs with a safe > rlimit.) SELinux/RT-LSM could do this, but i'm not sure about how > rlimits give this to you. How does it get done with RT-LSM? Setgid binaries? It only discriminates on a group granularity. Or are you saying "and SELinux" rather than "or SELinux"? -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
