linux-kernel - Re: [PATCH 2/2] sched: allow users with rtprio rlimit to change from SCHED

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Date:	Wed, 23 Feb 2011 12:03:09 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Darren Hart <dvhart@...ux.intel.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, richard.purdie@...uxfoundation.org
Subject: Re: [PATCH 2/2] sched: allow users with rtprio rlimit to change
 from SCHED_IDLE policy

On Tue, 2011-02-22 at 13:04 -0800, Darren Hart wrote:
> As it stands, users with rtprio rlimit permissions can change their policy from
> SCHED_OTHER to SCHED_FIFO and back. They can change to SCHED_IDLE, but not back
> to SCHED_FIFO. If they have the rtprio permission, they should be able to. Once
> in SCHED_FIFO, they could go back to SCHED_OTHER. This patch allows users with
> rtprio permission to change out of SCHED_IDLE.
> 

Ingo, can you remember the rationale for this?

The fact is that SCHED_IDLE is very near nice-20, and we can do:

peterz@...ns:~$ renice 5 -p $$
1867: old priority 0, new priority 5
peterz@...ns:~$ renice 0 -p $$
1867: old priority 5, new priority 0

Which would suggest that we should be able to return to SCHED_OTHER
RLIMIT_NICE-20.

Hmm?

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