Date: Mon, 7 May 2007 16:32:56 +0530
From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: Gautham R Shenoy <ego@in.ibm.com>
Cc: Satoru Takeuchi <takeuchi_satoru@jp.fujitsu.com>,
       Linux Kernel <linux-kernel@vger.kernel.org>,
       Rusty Russell <rusty@rustcorp.com.au>,
       Zwane Mwaikambo <zwane@arm.linux.org.uk>,
       Nathan Lynch <nathanl@austin.ibm.com>,
       Joel Schopp <jschopp@austin.ibm.com>, Ashok Raj <ashok.raj@intel.com>,
       Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: Re: [BUG] cpu-hotplug: Can't offline the CPU with naughty realtime processes
Message-ID: <20070507110256.GM7311@in.ibm.com>
Reply-To: vatsa@in.ibm.com
References: <87bqgxrlky.wl%takeuchi_satoru@jp.fujitsu.com> <20070507104724.GA10624@in.ibm.com>
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On Mon, May 07, 2007 at 04:17:24PM +0530, Gautham R Shenoy wrote:
> Nevertheless, with the freezer based approach that we're experimenting,
> this problem shouldn't arise. We expect the whole system to get frozen
> before we actually do a cpu_down() (which will then call
> __stop_machine_run). So any such rogue RT task will have to first fail
> the freezer ( which it will), 

>From what I understand of the freezer, if the RT task is running in user
space (which seems to be the case in this thread), it should get frozen even 
if it is a forever running SCHED_FIFO task at MAX_RT_PRIO -1 priority?

> but that's ok, since on a freezer-fail,
> we just thaw all the processes and get the system up and running again.
> Yeah, the cpu-hotplug operation will fail though.

-- 
Regards,
vatsa
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