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[for-next][PATCH 5/7] jump_label: Add comment about initialization order for anonymous unions

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From: "Steven Rostedt (VMware)" <rostedt@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.ostrovsky@oracle.com>
Suggested-by: Chris Mason <clm@fb.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@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

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[for-next][PATCH 0/7] tracing: Fixes for 4.11 Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100
  [for-next][PATCH 5/7] jump_label: Add comment about initialization order for anonymous  unions Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100
  [for-next][PATCH 2/7] ftrace/graph: Do not modify the EMPTY_HASH for the function_graph  filter Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100
  [for-next][PATCH 7/7] ftrace/graph: Add ftrace_graph_max_depth kernel parameter Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100
  [for-next][PATCH 1/7] tracing: Fix code comment for ftrace_ops_get_func() Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100
  [for-next][PATCH 3/7] module: set __jump_table alignment to 8 Steven Rostedt <rostedt@goodmis.org> - 2017-03-03 15:50 +0100

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