Re: + memory-hotplug-fix-kswapd-looping-forever-problem-fix-fix.patch added to -mm tree

[Tejun Heo <tj@kernel.org>]

Hello, Minchan.

On Mon, Jul 23, 2012 at 01:58:55PM +0900, Minchan Kim wrote:
> I would like to know what fields you are concerning because most of field

The above question itself is a problem.  It's subtle to hell.  Some
fields of this data structure is used during early boot but at some
point all are reset to zero, so we have to be careful about how those
fields are used before and after.

This might seem clear now but things like this are likely to make
people later working on the code go WTF.  Let's say for whatever
reason ->bdata needs to be accessed after free_area_init - e.g.
arch_add_memory() needs some info from bdata, what then?

What if we end up having to add a new property field which is
determined by platform code but used by generic code.  I would add a
field to pgdat, init it from numa.c and then later use it in generic
code.  If the field gets zeroed inbetween, I would get pretty annoyed.

I really don't think this subject is worth the amount of discussion we
had in this thread.  Just make the archs clear the data structure on
creation.  Anything else is silly.

Thanks.

-- 
tejun

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