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Date: Thu, 11 Jul 2002 09:15:23 +0200 (CEST)
From: Ingo Molnar <mingo@elte.hu>
Reply-To: Ingo Molnar <mingo@elte.hu>
To: oleg@tv-sign.ru
Cc: linux-kernel@vger.kernel.org
Subject: Re: [patch] sched-2.5.24-D3, batch/idle priority scheduling,
 SCHED_BATCH
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> > > And users of __KERNEL_SYSCALLS__ and kernel_thread() should not
> > > have policy == SCHED_BATCH.
> 
> well, there's one security consequence here - module loading
> (request_module()), which spawns a kernel thread must not run as
> SCHED_BATCH. I think the right solution for that path is to set the
> policy to SCHED_OTHER upon entry, and restore it to the previous one
> afterwards - this way the helper thread has SCHED_OTHER priority.

i've solved this problem by making kernel_thread() spawned threads drop
back to SCHED_NORMAL:

	http://redhat.com/~mingo/O(1)-scheduler/sched-2.5.25-A7

I believe this is the secure way of doing it - independently of
SCHED_BATCH - a RT task should not spawn a RT kernel thread 'unwillingly'.

	Ingo

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