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Date: Thu, 3 Dec 2015 17:45:54 -0500
From: Aaron Conole <aconole@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, Joe Perches <joe@...ches.com>
Subject: [PATCH] printk: fix pr_debug and pr_devel to elide function calls
Currently, pr_debug and pr_devel will not elide function call arguments
appearing in calls to no_printk for these macros. This is because all
side effects must be honored before proceeding to the 0-value assignment
in no_printk.
The behavior is contrary to documentation found in the CodingStyle and
header file where these functions are declared.
This patch corrects that behavior by shunting out the call to no_printk
completely. The format string is still checked by gcc for correctness, but
no code seems to be emitted in common cases.
fixes commit 5264f2f75d86 ("include/linux/printk.h: use and neaten
no_printk")
Signed-off-by: Aaron Conole <aconole@...hat.com>
Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Joe Perches <joe@...ches.com>
---
include/linux/printk.h | 42 +++++++++++++++++++++++++++++++++---------
1 file changed, 33 insertions(+), 9 deletions(-)
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 9729565..87dfdd2 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -270,8 +270,12 @@ extern asmlinkage void dump_stack(void) __cold;
#define pr_devel(fmt, ...) \
printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
-#define pr_devel(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_devel(fmt, ...) \
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
#include <linux/dynamic_debug.h>
@@ -286,7 +290,11 @@ extern asmlinkage void dump_stack(void) __cold;
printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
#define pr_debug(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
/*
@@ -341,7 +349,11 @@ extern asmlinkage void dump_stack(void) __cold;
printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
#define pr_devel_once(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
/* If you are writing a driver, please use dev_dbg instead */
@@ -350,7 +362,11 @@ extern asmlinkage void dump_stack(void) __cold;
printk_once(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
#define pr_debug_once(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
/*
@@ -392,8 +408,12 @@ extern asmlinkage void dump_stack(void) __cold;
#define pr_devel_ratelimited(fmt, ...) \
printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
-#define pr_devel_ratelimited(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_devel_ratelimited(fmt, ...) \
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
/* If you are writing a driver, please use dev_dbg instead */
@@ -413,8 +433,12 @@ do { \
#define pr_debug_ratelimited(fmt, ...) \
printk_ratelimited(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
#else
-#define pr_debug_ratelimited(fmt, ...) \
- no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_debug_ratelimited(fmt, ...) \
+do { \
+ if (0) { \
+ no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__);\
+ } \
+} while (0)
#endif
extern const struct file_operations kmsg_fops;
--
2.6.1.133.gf5b6079
--
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