Subject: [PATCH net-next,v2,1/2] once: implement DO_ONCE_LITE for non-fast-path "do once" functionality

From: Tanner Love <[email-masked]>
Date: Wed, 26 May 2021 19:13:35 -0400

From: Tanner Love <[email-masked]>

Certain uses of "do once" functionality reside outside of fast path,
and so do not require jump label patching via static keys, making
existing DO_ONCE undesirable in such cases.

Replace uses of __section(".data.once") with DO_ONCE_LITE(_IF)?

[ i386 build warnings ]
Reported-by: kernel test robot <[email-masked]>
Signed-off-by: Tanner Love <[email-masked]>
Acked-by: Eric Dumazet <[email-masked]>
Acked-by: Mahesh Bandewar <[email-masked]>
---
 fs/xfs/xfs_message.h      | 13 +++----------
 include/asm-generic/bug.h | 37 +++++++------------------------------
 include/linux/once_lite.h | 24 ++++++++++++++++++++++++
 include/linux/printk.h    | 23 +++--------------------
 kernel/trace/trace.h      | 13 +++----------
 5 files changed, 40 insertions(+), 70 deletions(-)
 create mode 100644 include/linux/once_lite.h

diff --git a/fs/xfs/xfs_message.h b/fs/xfs/xfs_message.h
index 3c392b1512ac..5daf73f21509 100644
--- a/fs/xfs/xfs_message.h
+++ b/fs/xfs/xfs_message.h
@@ -2,6 +2,8 @@
 #ifndef __XFS_MESSAGE_H
 #define __XFS_MESSAGE_H 1
 
+#include <linux/once_lite.h>
+
 struct xfs_mount;
 
 extern __printf(2, 3)
@@ -41,16 +43,7 @@ do {									\
 } while (0)
 
 #define xfs_printk_once(func, dev, fmt, ...)			\
-({								\
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once; 			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		func(dev, fmt, ##__VA_ARGS__);			\
-	}							\
-	unlikely(__ret_print_once);				\
-})
+	DO_ONCE_LITE(func, dev, fmt, ##__VA_ARGS__)
 
 #define xfs_emerg_ratelimited(dev, fmt, ...)				\
 	xfs_printk_ratelimited(xfs_emerg, dev, fmt, ##__VA_ARGS__)
diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
index b402494883b6..bafc51f483c4 100644
--- a/include/asm-generic/bug.h
+++ b/include/asm-generic/bug.h
@@ -4,6 +4,7 @@
 
 #include <linux/compiler.h>
 #include <linux/instrumentation.h>
+#include <linux/once_lite.h>
 
 #define CUT_HERE		"------------[ cut here ]------------\n"
 
@@ -140,39 +141,15 @@ void __warn(const char *file, int line, void *caller, unsigned taint,
 })
 
 #ifndef WARN_ON_ONCE
-#define WARN_ON_ONCE(condition)	({				\
-	static bool __section(".data.once") __warned;		\
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN_ON(1);					\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
+#define WARN_ON_ONCE(condition)					\
+	DO_ONCE_LITE_IF(condition, WARN_ON, 1)
 #endif
 
-#define WARN_ONCE(condition, format...)	({			\
-	static bool __section(".data.once") __warned;		\
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN(1, format);				\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
+#define WARN_ONCE(condition, format...)				\
+	DO_ONCE_LITE_IF(condition, WARN, 1, format)
 
-#define WARN_TAINT_ONCE(condition, taint, format...)	({	\
-	static bool __section(".data.once") __warned;		\
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		WARN_TAINT(1, taint, format);			\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
+#define WARN_TAINT_ONCE(condition, taint, format...)		\
+	DO_ONCE_LITE_IF(condition, WARN_TAINT, 1, taint, format)
 
 #else /* !CONFIG_BUG */
 #ifndef HAVE_ARCH_BUG
diff --git a/include/linux/once_lite.h b/include/linux/once_lite.h
new file mode 100644
index 000000000000..861e606b820f
--- /dev/null
+++ b/include/linux/once_lite.h
@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_ONCE_LITE_H
+#define _LINUX_ONCE_LITE_H
+
+#include <linux/types.h>
+
+/* Call a function once. Similar to DO_ONCE(), but does not use jump label
+ * patching via static keys.
+ */
+#define DO_ONCE_LITE(func, ...)						\
+	DO_ONCE_LITE_IF(true, func, ##__VA_ARGS__)
+#define DO_ONCE_LITE_IF(condition, func, ...)				\
+	({								\
+		static bool __section(".data.once") __already_done;	\
+		bool __ret_do_once = !!(condition);			\
+									\
+		if (unlikely(__ret_do_once && !__already_done)) {	\
+			__already_done = true;				\
+			func(__VA_ARGS__);				\
+		}							\
+		unlikely(__ret_do_once);				\
+	})
+
+#endif /* _LINUX_ONCE_LITE_H */
diff --git a/include/linux/printk.h b/include/linux/printk.h
index fe7eb2351610..885379a1c9a1 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -8,6 +8,7 @@
 #include <linux/linkage.h>
 #include <linux/cache.h>
 #include <linux/ratelimit_types.h>
+#include <linux/once_lite.h>
 
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
@@ -436,27 +437,9 @@ extern int kptr_restrict;
 
 #ifdef CONFIG_PRINTK
 #define printk_once(fmt, ...)					\
-({								\
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once;			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		printk(fmt, ##__VA_ARGS__);			\
-	}							\
-	unlikely(__ret_print_once);				\
-})
+	DO_ONCE_LITE(printk, fmt, ##__VA_ARGS__)
 #define printk_deferred_once(fmt, ...)				\
-({								\
-	static bool __section(".data.once") __print_once;	\
-	bool __ret_print_once = !__print_once;			\
-								\
-	if (!__print_once) {					\
-		__print_once = true;				\
-		printk_deferred(fmt, ##__VA_ARGS__);		\
-	}							\
-	unlikely(__ret_print_once);				\
-})
+	DO_ONCE_LITE(printk_deferred, fmt, ##__VA_ARGS__)
 #else
 #define printk_once(fmt, ...)					\
 	no_printk(fmt, ##__VA_ARGS__)
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index cd80d046c7a5..d5d8c088a55d 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -20,6 +20,7 @@
 #include <linux/irq_work.h>
 #include <linux/workqueue.h>
 #include <linux/ctype.h>
+#include <linux/once_lite.h>
 
 #ifdef CONFIG_FTRACE_SYSCALLS
 #include <asm/unistd.h>		/* For NR_SYSCALLS	     */
@@ -99,16 +100,8 @@ enum trace_type {
 #include "trace_entries.h"
 
 /* Use this for memory failure errors */
-#define MEM_FAIL(condition, fmt, ...) ({			\
-	static bool __section(".data.once") __warned;		\
-	int __ret_warn_once = !!(condition);			\
-								\
-	if (unlikely(__ret_warn_once && !__warned)) {		\
-		__warned = true;				\
-		pr_err("ERROR: " fmt, ##__VA_ARGS__);		\
-	}							\
-	unlikely(__ret_warn_once);				\
-})
+#define MEM_FAIL(condition, fmt, ...)					\
+	DO_ONCE_LITE_IF(condition, pr_err, "ERROR: " fmt, ##__VA_ARGS__)
 
 /*
  * syscalls are special, and need special handling, this is why
-- 
2.32.0.rc0.204.g9fa02ecfa5-goog