The patch titled
Subject: printk: help pr_debug and pr_devel to optimize out arguments
has been added to the -mm tree. Its filename is
printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments.patch
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------------------------------------------------------
From: Aaron Conole <aconole@xxxxxxxxxx>
Subject: printk: help pr_debug and pr_devel to optimize out arguments
Currently, pr_debug and pr_devel will not elide function call arguments
appearing in calls to the 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 the
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: 5264f2f75d86 ("include/linux/printk.h: use and neaten no_printk")
Signed-off-by: Aaron Conole <aconole@xxxxxxxxxx>
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Joe Perches <joe@xxxxxxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/printk.h | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff -puN include/linux/printk.h~printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments include/linux/printk.h
--- a/include/linux/printk.h~printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments
+++ a/include/linux/printk.h
@@ -106,13 +106,14 @@ struct va_format {
/*
* Dummy printk for disabled debugging statements to use whilst maintaining
- * gcc's format and side-effect checking.
+ * gcc's format checking.
*/
-static inline __printf(1, 2)
-int no_printk(const char *fmt, ...)
-{
- return 0;
-}
+#define no_printk(fmt, ...) \
+do { \
+ if (0) { \
+ printk(fmt, ##__VA_ARGS__); \
+ } \
+} while (0)
#ifdef CONFIG_EARLY_PRINTK
extern asmlinkage __printf(1, 2)
_
Patches currently in -mm which might be from aconole@xxxxxxxxxx are
printk-help-pr_debug-and-pr_devel-to-optimize-out-arguments.patch
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