linux-kernel - [RFC PATCH] dynamic_debug: only add header when used

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Date:	Wed, 13 Jul 2016 18:09:53 +0100
From:	Luis de Bethencourt <luisbg@....samsung.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, rusty@...tcorp.com.au,
	hidehiro.kawai.ez@...achi.com, bp@...e.de, mina86@...a86.com,
	linux@...musvillemoes.dk, joe@...ches.com,
	Luis de Bethencourt <luisbg@....samsung.com>
Subject: [RFC PATCH] dynamic_debug: only add header when used

kernel.h header doesn't directly use dynamic debug, instead we can include
it in module.c (which used it via kernel.h). printk.h only uses it if
CONFIG_DYNAMIC_DEBUG is on, changing the inclusion to only happen in that
case.

Signed-off-by: Luis de Bethencourt <luisbg@....samsung.com>
---
Hi,

While studying the problem that surfaced when adding #include <linux/kernel.h>
in include/linux/string.h to have access to the MAX_SIZE macro [0]. I noticed
that dynamic_debug.h is included in kernel.h even though it isn't necessary.
Which in the case of adding kernel.h to string.h would mean a circular
dependency.

Not entirely sure if there is a reason for this beyond making dynamic debug
available to module.c. Which is why I am sending this patch as an RFC.

Thanks for the feedback,
Luis


[0] https://lkml.org/lkml/2016/7/11/753

 include/linux/kernel.h | 1 -
 include/linux/printk.h | 3 ++-
 kernel/module.c        | 1 +
 3 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index c420821..d96a611 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -11,7 +11,6 @@
 #include <linux/log2.h>
 #include <linux/typecheck.h>
 #include <linux/printk.h>
-#include <linux/dynamic_debug.h>
 #include <asm/byteorder.h>
 #include <uapi/linux/kernel.h>
 
diff --git a/include/linux/printk.h b/include/linux/printk.h
index 41ac0fc..c2158f0 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -307,10 +307,11 @@ asmlinkage __printf(1, 2) __cold void __pr_info(const char *fmt, ...);
 	no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__)
 #endif
 
-#include <linux/dynamic_debug.h>
 
 /* If you are writing a driver, please use dev_dbg instead */
 #if defined(CONFIG_DYNAMIC_DEBUG)
+#include <linux/dynamic_debug.h>
+
 /* dynamic_pr_debug() uses pr_fmt() internally so we don't need it here */
 #define pr_debug(fmt, ...) \
 	dynamic_pr_debug(fmt, ##__VA_ARGS__)
diff --git a/kernel/module.c b/kernel/module.c
index beaebea..e70a2fa 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -60,6 +60,7 @@
 #include <linux/jump_label.h>
 #include <linux/pfn.h>
 #include <linux/bsearch.h>
+#include <linux/dynamic_debug.h>
 #include <uapi/linux/module.h>
 #include "module-internal.h"
 
-- 
2.5.1