linux-kernel - [RFC PATCH v2 1/5] jump_label: split out declaration parts into its own headers

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Date:   Fri,  9 Oct 2020 14:29:22 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     Mel Gorman <mgorman@...e.de>,
        Frederic Weisbecker <fweisbecker@...e.de>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [RFC PATCH v2 1/5] jump_label: split out declaration parts into its own headers

From: Michal Hocko <mhocko@...e.com>

Follow up patch would like to add a static key into kernel.h and that
requires a declaration of the key in the same file. Including
jump_label.h into kernel.h is not possible due to headers dependencies.

Separate parts needed for declaration into its own header which doesn't
depend on any other header file. kernel.h can include jump_abel_type.h.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 include/linux/jump_label.h      | 44 +----------------------------
 include/linux/jump_label_type.h | 49 +++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 43 deletions(-)
 create mode 100644 include/linux/jump_label_type.h

diff --git a/include/linux/jump_label.h b/include/linux/jump_label.h
index 32809624d422..bd0d846d0bde 100644
--- a/include/linux/jump_label.h
+++ b/include/linux/jump_label.h
@@ -75,6 +75,7 @@
 
 #include <linux/types.h>
 #include <linux/compiler.h>
+#include <linux/jump_label_type.h>
 
 extern bool static_key_initialized;
 
@@ -82,35 +83,6 @@ extern bool static_key_initialized;
 				    "%s(): static key '%pS' used before call to jump_label_init()", \
 				    __func__, (key))
 
-#ifdef CONFIG_JUMP_LABEL
-
-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
- *	    0 if points to struct jump_entry
- */
-	union {
-		unsigned long type;
-		struct jump_entry *entries;
-		struct static_key_mod *next;
-	};
-};
-
-#else
-struct static_key {
-	atomic_t enabled;
-};
-#endif	/* CONFIG_JUMP_LABEL */
 #endif /* __ASSEMBLY__ */
 
 #ifdef CONFIG_JUMP_LABEL
@@ -343,14 +315,6 @@ static inline void static_key_disable(struct static_key *key)
  * All the below code is macros in order to play type games.
  */
 
-struct static_key_true {
-	struct static_key key;
-};
-
-struct static_key_false {
-	struct static_key key;
-};
-
 #define STATIC_KEY_TRUE_INIT  (struct static_key_true) { .key = STATIC_KEY_INIT_TRUE,  }
 #define STATIC_KEY_FALSE_INIT (struct static_key_false){ .key = STATIC_KEY_INIT_FALSE, }
 
@@ -360,18 +324,12 @@ struct static_key_false {
 #define DEFINE_STATIC_KEY_TRUE_RO(name)	\
 	struct static_key_true name __ro_after_init = STATIC_KEY_TRUE_INIT
 
-#define DECLARE_STATIC_KEY_TRUE(name)	\
-	extern struct static_key_true name
-
 #define DEFINE_STATIC_KEY_FALSE(name)	\
 	struct static_key_false name = STATIC_KEY_FALSE_INIT
 
 #define DEFINE_STATIC_KEY_FALSE_RO(name)	\
 	struct static_key_false name __ro_after_init = STATIC_KEY_FALSE_INIT
 
-#define DECLARE_STATIC_KEY_FALSE(name)	\
-	extern struct static_key_false name
-
 #define DEFINE_STATIC_KEY_ARRAY_TRUE(name, count)		\
 	struct static_key_true name[count] = {			\
 		[0 ... (count) - 1] = STATIC_KEY_TRUE_INIT,	\
diff --git a/include/linux/jump_label_type.h b/include/linux/jump_label_type.h
new file mode 100644
index 000000000000..37cb02c12f35
--- /dev/null
+++ b/include/linux/jump_label_type.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_JUMP_LABEL_TYPE_H
+#define _LINUX_JUMP_LABEL_TYPE_H
+
+#ifdef CONFIG_JUMP_LABEL
+
+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
+ *	    0 if points to struct jump_entry
+ */
+	union {
+		unsigned long type;
+		struct jump_entry *entries;
+		struct static_key_mod *next;
+	};
+};
+
+#else
+struct static_key {
+	atomic_t enabled;
+};
+#endif	/* CONFIG_JUMP_LABEL */
+
+struct static_key_true {
+	struct static_key key;
+};
+
+struct static_key_false {
+	struct static_key key;
+};
+
+#define DECLARE_STATIC_KEY_TRUE(name)	\
+	extern struct static_key_true name
+
+#define DECLARE_STATIC_KEY_FALSE(name)	\
+	extern struct static_key_false name
+
+#endif /* _LINUX_JUMP_LABEL_TYPE_H */
-- 
2.28.0