[PATCH] powerpc/mobility: Fix node detach/rename problem

[Michael Ellerman]

Michael Bringmann <mwb at linux.vnet.ibm.com> writes:

> During LPAR migration, the content of the device tree/sysfs may
> be updated including deletion and replacement of nodes in the
> tree.  When nodes are added to the internal node structures, they
> are appended in FIFO order to a list of nodes maintained by the
> OF code APIs.

That hasn't been true for several years. The data structure is an n-ary
tree. What kernel version are you working on?

> When nodes are removed from the device tree, they
> are marked OF_DETACHED, but not actually deleted from the system
> to allow for pointers cached elsewhere in the kernel.  The order
> and content of the entries in the list of nodes is not altered,
> though.

Something is going wrong if this is actually happening.

When the node is detached it should be *detached* from the tree of all
nodes, so it should not be discoverable other than by having an existing
pointer to it.

That's what __of_detach_node() does:

	parent = np->parent;
	if (WARN_ON(!parent))
		return;

	if (parent->child == np)
		parent->child = np->sibling;
	else {
		struct device_node *prevsib;
		for (prevsib = np->parent->child;
		     prevsib->sibling != np;
		     prevsib = prevsib->sibling)
			;
		prevsib->sibling = np->sibling;
	}

ie. the node must already have a NULL parent, and then it is spliced out
of its parent's child list.


Please give us more info so we can work out what's actually happening.

cheers