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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-03-02 17:28:45 -0500
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2017-03-03 09:45:00 -0500
commitb17ef2ed624aa7c1f68ed11acd16ecbf80fe01d7 (patch)
treebcad6c5b7af4f880d1f52370cfa84632ba94cef9 /include/linux/jump_label.h
parentcd8d860dcce906cd477be7d0648ba6f56a52eaa6 (diff)
jump_label: Add comment about initialization order for anonymous unions
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>
Diffstat (limited to 'include/linux/jump_label.h')
-rw-r--r--include/linux/jump_label.h7
1 files changed, 7 insertions, 0 deletions
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