Merging upstream version 6.10.3.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 11 insertions, 1 deletions

diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h
index 6c37d94a37..494f68cc13 100644
--- a/kernel/time/timer_migration.h
+++ b/kernel/time/timer_migration.h
@@ -22,7 +22,17 @@ struct tmigr_event {
  * struct tmigr_group - timer migration hierarchy group
  * @lock:		Lock protecting the event information and group hierarchy
  *			information during setup
- * @parent:		Pointer to the parent group
+ * @parent:		Pointer to the parent group. Pointer is updated when a
+ *			new hierarchy level is added because of a CPU coming
+ *			online the first time. Once it is set, the pointer will
+ *			not be removed or updated. When accessing parent pointer
+ *			lock less to decide whether to abort a propagation or
+ *			not, it is not a problem. The worst outcome is an
+ *			unnecessary/early CPU wake up. But do not access parent
+ *			pointer several times in the same 'action' (like
+ *			activation, deactivation, check for remote expiry,...)
+ *			without holding the lock as it is not ensured that value
+ *			will not change.
  * @groupevt:		Next event of the group which is only used when the
  *			group is !active. The group event is then queued into
  *			the parent timer queue.