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SubjectRe: + hugetlb-fix-section-mismatch-warning-in-hugetlbc.patch added to -mm tree
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On Fri, 2010-01-08 at 12:34 +0600, Rakib Mullick wrote:
> On 1/8/10, Randy Dunlap <randy.dunlap@oracle.com> wrote:
>
> Hi,
> >
> > Hi,
> >
> > If so, then hugetlb_register_node() could be called at any time
> > (like after system init), and it would then call
> > hugetlb_sysfs_add_hstate(), which would be bad.
> >
> But - hugetlb_register_node is only called from hugetlb_register_all_nodes.

No, hugetlb_register_node() is also called from the similarly named
function in drivers/base/node.c. mm/hugetlb.c registers its version of
"hugetlb_register_node()" at start up for use at node hotplug. See
register_hugetlbfs_with_node() in node.c and its use in hugetlb.c.

We had to do it this way because node.c is part of the base kernel and
hugetlb support can be built as a module. All sysfs node kobjs have
been registered by the time hugetlb inits, so hugetlb registers the
nodes' hstate attributes when it initializes. However, when a node is
hotplugged later, the node driver calls into hugetlb to register the
attributes.

So, we need to keep mm/hugetlb.c:hugetlb_register_node() around during
run time when mem/node hot-plug is supported.

Lee


> The call sequence is :
> hugetlb_init ---------------> was __init
> \-> hugetlb_register_all_nodes ----> we make it __init
> \-> hugetlb_register_node
> ---> we make it __init
> \->
> hugetlb_sysfs_add_hstate -> this was __init
>
> Above all happens in __init context. So - hugetlb_register_node is
> called only at
> system init. But I don't think __init is used for hotplug support, for
> proper hotplug
> support we might use __meminit.
>
> And register_hugetlbfs_with_node is called from hugetlb_un/register_node.
> But hugetlb_unregister_node doesn't use callback function. It's not referencing
> hugetlb_sysfs_add_hstate(). So - it's safe. Unless I'm not missing
> anything, too.
>
> thanks,
>
> > Thanks.
> > ---
> >
> > ~Randy
> >
>
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