Re: Where is RLIMIT_RT_CPU?

From: Esben Nielsen
Date: Fri Jul 14 2006 - 16:29:54 EST




On Fri, 14 Jul 2006, Jean-Marc Valin wrote:

It was not merged.

This problem should be addressed by a userspace RT watchdog. Ubuntu
should not have shipped their system with unlimited non-root realtime
enabled and no watchdog.

Does such a daemon currently exist? Even then, is there any way to
police all unprivileged RT apps without introducing an O(N) operation
running continuously at max rt priority? Sort of defeats the purpose of
having an O(1) scheduler, no? I assume the RT check can be some in O(1)
time in the kernel, right?


Can't you just make a prio 1 task which signals a prio 99 once say every second. If the priority 99 task doesn't get the signal after say 2 seconds, it will look for a rt task running wild. At worst it will have to do
an O(n) algorith when things have gone wrong, not when everything is working.

Esben

About Ubuntu, I agree it wasn't a smart thing to do (I'm not an Ubuntu
devel, so I don't know what the reason was), but it would be nice if
this could be fixed without having to entirely remove the unprivileged
real-time feature. In the end, I'm not sure what the best solution is
(just an RT audio developer).

Jean-Marc
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