Message-ID: <41402F73.6060804@yahoo.com.au>
Date: Thu, 09 Sep 2004 20:24:51 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Rusty Russell <rusty@rustcorp.com.au>
CC: Nathan Lynch <nathanl@austin.ibm.com>,
       linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 2/3] cpu: add a CPU_DOWN_PREPARE notifier
References: <413EFFFB.5050902@yahoo.com.au>  <413F0070.2020104@yahoo.com.au> <1094725418.25641.21.camel@bach>
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Rusty Russell wrote:
> On Wed, 2004-09-08 at 22:52, Nick Piggin wrote:
> 
>>2/3
>>
>>Rusty, can I do this?
>>
>>______________________________________________________________________
>>Add a CPU_DOWN_PREPARE hotplug CPU notifier. This is needed so we can
>>dettach all sched-domains before a CPU goes down, thus we can build
>>domains from online cpumasks, and not have to check for the possibility
>>of a CPU coming up or going down.
> 
> 
> And if taking the CPU down fails?  If you need this, you need the
> CPU_DOWN_FAILED as well, unfortunately.  Hence I prefer the "do the
> domain thing while machine is frozen" and sidestep it entirely.
> 

Really? It doesn't need to be run from the stop_machine_run
context at all - it can happily be done while the system is
running.

That said, if you really object to CPU_DOWN_PREPARE and CPU_DOWN_FAILED,
it probably shouldn't be too much work. Should it make the call from
take_cpu_down?
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