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SubjectRe: [PATCH] x86: split e820 reserved entries record to late v4 - fix


On Fri, 29 Aug 2008, Yinghai Lu wrote:
>
> try to insert_resource second time, by expand the resource...

I would hold off on this unless it's shown to actually be needed. And _if_
it is needed, I would just make a new function for doing this all:
"insert_resource_expand_to_fit()"

That said, I think the insert_resource()/__insert_resource() change is
pretty ok. However, it doesn't follow the rules, and is racy. The rules
for resources are:

- the "internal" version (with the "__" prepended) is static to
resource.c, because it must not be called from outside, which is in
turn because:

- it must be called with the lock taken by the caller, because otherwise
returning a "struct resource *" is racy - the resource is not protected
by anything!

So the "insert_resource_expand_to_fit()" thing would look something like
this:

void insert_resource_expand_to_fit(struct resource *root, struct resource *new)
{
write_lock(&resource_lock);
while (new->start && new->parent) {
struct resource *conflict;
conflict = __insert_resource(root, new);
if (!conflict)
break;
if (conflict->start < new->start)
new->start = conflict->start;
if (conflict->end > new->end)
new->end = conflict->end;
}
write_unlock(&resource_lock);
}
but the above is obviously _totally_ untested.

Linus


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