Re: [PATCH] sched: Don't allow priority switch to realtime whenthe task doesn't belong to init_task_group and whenCONFIG_RT_GROUP_SCHED isn't set

From: Srivatsa Vaddagiri
Date: Mon Nov 24 2008 - 12:05:55 EST


On Mon, Nov 24, 2008 at 09:32:06AM +0100, Peter Zijlstra wrote:
> > And may be as Ingo
> > suggested they should be moved to init_task_group.
>
> Bzzt, wrong! They should not be moved to any group, they cannot be moved
> to any group, as they are group invariant.

Though what you say makes sense, the confusion arises from existing
cgroup<->scheduler interface, which can end up showing the above
single-set of RT-tasks to be split into multiple sets.

RT Tasks -> {RT0, RT1}

can be shown as:

/a/tasks {RT0, ...}
/b/tasks {RT1, ...}

Does this cause any problems? Perhaps no, just seems odd ..

Fixing this oddity of representing single RT-tasks set as multiple is not a
cgroup issue IMHO.

P.S :- If eventually RT_GROUP_SCHED will be merged with FAIR_GROUP_SCHED, then
it may make sense for us to just ignore this oddity for timebeing and look
forward to the options being merged.

- vatsa
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