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Message-ID: <alpine.LFD.1.10.0808290854000.3300@nehalem.linux-foundation.org>
Date: Fri, 29 Aug 2008 09:05:16 -0700 (PDT)
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Yinghai Lu <yhlu.kernel@...il.com>
cc: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
"H. Peter Anvin" <hpa@...or.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
linux-kernel@...r.kernel.org
Subject: Re: [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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