of: dynamic: Synchronize of_changeset_destroy() with the devlink removals

commit 8917e7385346bd6584890ed362985c219fe6ae84 upstream.

In the following sequence:
  1) of_platform_depopulate()
  2) of_overlay_remove()

During the step 1, devices are destroyed and devlinks are removed.
During the step 2, OF nodes are destroyed but
__of_changeset_entry_destroy() can raise warnings related to missing
of_node_put():
  ERROR: memory leak, expected refcount 1 instead of 2 ...

Indeed, during the devlink removals performed at step 1, the removal
itself releasing the device (and the attached of_node) is done by a job
queued in a workqueue and so, it is done asynchronously with respect to
function calls.
When the warning is present, of_node_put() will be called but wrongly
too late from the workqueue job.

In order to be sure that any ongoing devlink removals are done before
the of_node destruction, synchronize the of_changeset_destroy() with the
devlink removals.

Fixes: 80dd33cf72d1 ("drivers: base: Fix device link removal")
Cc: stable@vger.kernel.org
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Nuno Sa <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20240325152140.198219-3-herve.codina@bootlin.com
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/of/dynamic.c b/drivers/of/dynamic.c
index 3bf27052832f302ac72d366b986629e03db4e900..4d57a4e34105466f8997b210271b231d216cb9b5 100644 (file)
--- a/drivers/of/dynamic.c
+++ b/drivers/of/dynamic.c
@@ -9,6 +9,7 @@
 
 #define pr_fmt(fmt)    "OF: " fmt
 
+#include <linux/device.h>
 #include <linux/of.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
@@ -667,6 +668,17 @@ void of_changeset_destroy(struct of_changeset *ocs)
 {
        struct of_changeset_entry *ce, *cen;
 
+       /*
+        * When a device is deleted, the device links to/from it are also queued
+        * for deletion. Until these device links are freed, the devices
+        * themselves aren't freed. If the device being deleted is due to an
+        * overlay change, this device might be holding a reference to a device
+        * node that will be freed. So, wait until all already pending device
+        * links are deleted before freeing a device node. This ensures we don't
+        * free any device node that has a non-zero reference count.
+        */
+       device_link_wait_removal();
+
        list_for_each_entry_safe_reverse(ce, cen, &ocs->entries, node)
                __of_changeset_entry_destroy(ce);
 }