Releasing resources with children
What does it mean to release a resource with children? Should the
children become children of the released resource's parent? Should they
be released too? Should we fail the release?
I bet we have no callers who expect this right now, but with
insert_resource() we may get some. At the point where someone hits this
BUG we can figure out what semantics we want.
Signed-off-by: Matthew Wilcox <[email protected]>
diff -urpNX dontdiff linux-2.6.11-bk10/kernel/resource.c parisc-2.6-bk/kernel/resource.c
--- linux-2.6.11-bk10/kernel/resource.c 2005-03-14 06:44:08.205342005 -0700
+++ parisc-2.6-bk/kernel/resource.c 2005-03-14 07:07:54.000000000 -0700
@@ -181,6 +181,8 @@ static int __release_resource(struct res
{
struct resource *tmp, **p;
+ BUG_ON(old->child);
+
p = &old->parent->child;
for (;;) {
tmp = *p;
On Mon, Mar 14, 2005 at 10:49:16AM -0700, Matthew Wilcox wrote:
> What does it mean to release a resource with children? Should the
> children become children of the released resource's parent? Should they
> be released too? Should we fail the release?
I've been running kernels with:
+ if (old->child) {
+ printk("Resource %p still has children: %s\n", old, old->name);
+ return -EINVAL;
+ }
+
here and it hasn't triggered once. I suspect the reason it hasn't is
because no one does release a resource with children, but I suspect
that's just by mere luck than design.
The only thing I'd question is whether we really need to BUG_ON() here.
ISTR Linus' policy for BUG()/BUG_ON() was only if the condition lead
directly to a filesystem-corrupting bug.
--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/
maintainer of: 2.6 Serial core
Russell King wrote:
> The only thing I'd question is whether we really need to BUG_ON() here.
> ISTR Linus' policy for BUG()/BUG_ON() was only if the condition lead
> directly to a filesystem-corrupting bug.
I consider it quite effective to flag interface violations.
Programming by contract anyone? ;-)
Regards
Ingo Oeser