Re: [PATCH 2/2] powerpc/pseries/dlpar: Remove DT entries if failure from CPU ADD notifier

On Wed, 2026-09-16 at 16:33 -0500, Rob Herring wrote:

On Tue, Sep 15, 2026 at 09:32:49PM -0700, Haren Myneni wrote:

quoted

For CPU ADD, the device tree entries are retrieved with
configure-connector RTAS call and attached to the device tree.
Then the CPU is added as part of DT node notification. If the CPU
ADD notifier returns failure, the corresponding CPU node entries
should be deleted from the device-tree. See pseries_add_processor()
for the possible failure cases.

The current code does not remove CPU node entries during CPU ADD
notifier failure and causing the following issues:
- Can not add this CPU later since already present in the
  device-tree.
- Trying to free memory allocated to CPU node without detaching
  the node and it causes freeing its sibling node (existing CPU
  nodes).

This patch fixes this issue by calling of_detach_node_no_notify()
for the failure from CPU ADD notifier which removes CPU node
entries without calling CPU REMOVE notifier.

Would using the of_changeset_ API directly solve your issue? It's
better 
designed for handling reverting a changeset. The of_attach_node/ 
of_detach_node() APIs have limited users and I'd really like to
remove 
them. Or make them PPC specific perhaps. Looks like there is 1 non-
PPC 
user that snuck in.

Thanks for your comments.

of_changeset_apply(): After adding all entries, calls notifiers for
each node and continue even after one notifier  failure and returns
failure. The caller does not know whether the failure is from attach
node or notifier and from which node. So
__of_changeset_revert_entries() can be used to revert entries if
stopped on the first failure.

of_changeset_revert(): always calls notifier for each node. I can use
__of_changeset_revert_entries() since CPU add has just one notifier but
not a standard interface.

pseries_cpuhp_attach_nodes():

if (!of_node_check_flag(np, OF_DETACHED))
	__of_changeset_revert_entries(&cs, *ret);

The current code calls dlpar_detach_node() if online CPU failed after
success from of_changeset_apply(). Hence added
of_detach_node_no_notify(). PPC code calls of_changeset_apply() for
multiple nodes and of_attach_node/of_detach_node for single node. 

 Or defining some other node flag OF_NOTIFIED to call the notifier for
revert / detach in of_changeset_*. 
 
Please let me know if you prefer to change of_changeset_*() instead of
of_detach_node_no_notify(0.

- Haren

Rob