[PATCH v2 05/45] reboot: Warn if restart handler has duplicated priority

Dmitry Osipenko
2021-10-27T21:18:48Z

Add sanity check which ensures that there are no two restart handlers
registered with the same priority. Normally it's a direct sign of a
problem if two handlers use the same priority.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
kernel/reboot.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/kernel/reboot.c b/kernel/reboot.c
index efb40d095d1e..d39e599c3c99 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -182,7 +182,20 @@ static ATOMIC_NOTIFIER_HEAD(restart_handler_list);
*/
int register_restart_handler(struct notifier_block *nb)
{
- return atomic_notifier_chain_register(&restart_handler_list, nb);
+ int ret;
+
+ ret = atomic_notifier_chain_register(&restart_handler_list, nb);
+ if (ret)
+ return ret;
+
+ /*
+ * Handler must have unique priority. Otherwise invocation order is
+ * determined by the registration order, which is presumed to be
+ * unreliable.
+ */
+ WARN_ON(!atomic_notifier_has_unique_priority(&restart_handler_list, nb));
+
+ return 0;
}
EXPORT_SYMBOL(register_restart_handler);

--
2.33.1