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Subject[PATCH 07/10] dynamic debug: resurrect old pr_debug() semantics as pr_devel()
From: Michael Ellerman <>

pr_debug() used to produce zero code unless DEBUG was #defined. This is
now no longer the case in practice[1].

There are places where it's useful to have debugging printks, but we don't
want them to generate any code in production kernels.

So add a new macro, pr_devel(), for _devel_opment, to provide the old
semantics, ie. if the programmer doesn't explicitly enable debugging, no
code is produced.

[1]: You can turn CONFIG_DYNAMIC_DEBUG off, but it's enabled in at least
one distro kernel, so it's not really a solution.

Signed-off-by: Michael Ellerman <>
Cc: Jason Baron <>
Cc: Greg Banks <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Greg Kroah-Hartman <>
include/linux/kernel.h | 9 +++++++++
1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d9e75ec..883cd44 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -377,6 +377,15 @@ static inline char *pack_hex_byte(char *buf, u8 byte)
#define pr_cont(fmt, ...) \
printk(KERN_CONT fmt, ##__VA_ARGS__)

+/* pr_devel() should produce zero code unless DEBUG is defined */
+#ifdef DEBUG
+#define pr_devel(fmt, ...) \
+ printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
+#define pr_devel(fmt, ...) \
+ ({ if (0) printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); 0; })
/* If you are writing a driver, please use dev_dbg instead */
#if defined(DEBUG)
#define pr_debug(fmt, ...) \

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