Commit a358f406 authored by Tanner Love's avatar Tanner Love Committed by David S. Miller
Browse files

once: implement DO_ONCE_LITE for non-fast-path "do once" functionality 



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)?

This patch changes the return values of xfs_printk_once, printk_once,
and printk_deferred_once. Before, they returned whether the print was
performed, but now, they always return true. This is okay because the
return values of the following macros are entirely ignored throughout
the kernel:
- xfs_printk_once
- xfs_warn_once
- xfs_notice_once
- xfs_info_once
- printk_once
- pr_emerg_once
- pr_alert_once
- pr_crit_once
- pr_err_once
- pr_warn_once
- pr_notice_once
- pr_info_once
- pr_devel_once
- pr_debug_once
- printk_deferred_once
- orc_warn

Changes
v3:
  - Expand commit message to explain why changing return values of
    xfs_printk_once, printk_once, printk_deferred_once is benign
v2:
  - Fix i386 build warnings

Signed-off-by: default avatarTanner Love <tannerlove@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarMahesh Bandewar <maheshb@google.com>
Acked-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b74ef9f9

fs/xfs/xfs_message.h

+3 −10
Original line number Diff line number Diff line
@@ -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__)

include/asm-generic/bug.h

+7 −30
Original line number Diff line number Diff line
@@ -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

include/linux/once_lite.h

0 → 100644
+24 −0
Original line number Diff line number Diff line 
/* 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 */

include/linux/printk.h

+3 −20
Original line number Diff line number Diff line
@@ -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__)

kernel/trace/trace.h

+3 −10
Original line number Diff line number Diff line
@@ -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