linux-kernel - Re: [BUG] cpu-hotplug: Can't offline the CPU with naughty realtime processes

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Message-Id: <1178597046.28438.31.camel@localhost.localdomain>
Date:	Tue, 08 May 2007 14:04:06 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Satoru Takeuchi <takeuchi_satoru@...fujitsu.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Zwane Mwaikambo <zwane@....linux.org.uk>,
	Nathan Lynch <nathanl@...tin.ibm.com>,
	Joel Schopp <jschopp@...tin.ibm.com>,
	Ashok Raj <ashok.raj@...el.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Gautham R Shenoy <ego@...ibm.com>
Subject: Re: [BUG] cpu-hotplug: Can't offline the CPU with
	naughty	realtime	processes

On Tue, 2007-05-08 at 12:29 +0900, Satoru Takeuchi wrote:
> At Tue, 08 May 2007 13:02:25 +1000,
> Rusty Russell wrote:
> > We used to be able to create kernel threads higher than any userspace
> > priority.  If this is no longer true, I think that's OK: equal priority
> > still means we'll get scheduled, right?
> 
> IF SCHED_RR, yes. However, if SCHED_FIFO, no. Such process doen't have timeslice
> and only relinquish CPU time voluntarily.
> 
> # Hence this problem is complicated ;-(

OK, well, I agree with "don't do that" then 8)

Thanks,
Rusty.

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