Re: [PATCH] flush_cpu_workqueue: don't flush an empty ->worklist

[Srivatsa Vaddagiri]

On Mon, Jan 08, 2007 at 03:54:28PM -0800, Andrew Morton wrote:
> Furthermore I don't know which of these need to be tossed overboard if/when
> we get around to using the task freezer for CPU hotplug synchronisation.
> Hopefully, a lot of them.  I don't really understand why we're continuing
> to struggle with the existing approach before that question is settled.

Good point!

Fundamentally, I think we need to answer this question:

"Do we provide *some* mechanism to block concurrent hotplug operations
from happening? By hotplug operations I mean both changes to the bitmap
and execution of all baclbacks in CPU_DEAD/ONLINE etc"

If NO, then IMHO we will be forever fixing races

If YES, then what is that mechanism? freeze_processes()? or a magical
lock?

freeze_processes() cant be that mechanism, if my understanding of it is
correct - see http://lkml.org/lkml/2007/1/8/149 and 
http://marc.theaimsgroup.com/?l=linux-kernel&m=116817460726058.

I would be happy to be corrected if the above impression of
freeze_processes() is corrected ..

-- 
Regards,
vatsa
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