linux-kernel - Re: Where is RLIMIT_RT

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Date:	Sat, 15 Jul 2006 09:58:15 -0400
From:	Lee Revell <rlrevell@...-job.com>
To:	Jean-Marc Valin <Jean-Marc.Valin@...erbrooke.ca>
Cc:	Esben Nielsen <nielsen.esben@...glemail.com>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>
Subject: Re: Where is RLIMIT_RT_CPU?

On Sat, 2006-07-15 at 09:20 +1000, Jean-Marc Valin wrote:
> > 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.
> 
> Well, that would work in sort of preventing a complete lockup, but the
> watchdog wouldn't even know if the task eating lots of CPU is privileged
> (OK) or unprivileged (not OK). Also, the original RLIMIT_RT_CPU feature
> allowed you to really control how much CPU is available to unprivileged
> users, not just prevent them from getting 100% CPU. 

Non-root RT tasks are not "unprivileged" - they have a level of
privileges between a normal user and root.  Really I think it's OK for
these tasks to consume 100% CPU, as the admin has explicitly allowed it.

The only problem is that Ubuntu shipped with this enabled for everyone.

Lee

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