From: "Steven Rostedt (VMware)" <rost...@goodmis.org>
Commit 3821fd35b58d ("jump_label: Reduce the size of struct static_key")
broke old compilers that could not handle static initialization of anonymous
unions. Boris fixed it with a patch that added brackets around the static
initializer. But this creates a dependency between those initializers and
the structure's order of its fields. Document this dependency in case new
fields are added to struct static_key in the future.
Noted-by: Boris Ostrovsky <boris.ostrov...@oracle.com>
Suggested-by: Chris Mason <c...@fb.com>
Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org>
---
include/linux/jump_label.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index a7f90117cf7d..28e04a33535a 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -90,6 +90,13 @@ extern bool static_key_initialized;
struct static_key {
atomic_t enabled;
/*
+ * Note:
+ * To make anonymous unions work with old compilers, the static
+ * initialization of them requires brackets. This creates a dependency
+ * on the order of the struct with the initializers. If any fields
+ * are added, STATIC_KEY_INIT_TRUE and STATIC_KEY_INIT_FALSE may need
+ * to be modified.
+ *
* bit 0 => 1 if key is initially true
* 0 if initially false
* bit 1 => 1 if points to struct static_key_mod
--
2.10.2
