[RFC PATCH] dynamic_debug: only add header when used

[RFC PATCH] dynamic_debug: only add header when used

[Luis de Bethencourt]

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@osg.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

Re: [RFC PATCH] dynamic_debug: only add header when used

[Andrew Morton]

On Wed, 13 Jul 2016 18:09:53 +0100 Luis de Bethencourt <luisbg@osg.samsung.com> wrote:

> 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@osg.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.

It would be good if we can do this.

What is it in kernel.h that requires dynamic_debug.h?  I tried your
patch along with

--- a/kernel/module.c~dynamic_debug-only-add-header-when-used-fix
+++ a/kernel/module.c
@@ -60,7 +60,6 @@
 #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"
 
and module.o builds OK.

Re: [RFC PATCH] dynamic_debug: only add header when used

[Luis de Bethencourt]

On 13/07/16 21:32, Andrew Morton wrote:
> On Wed, 13 Jul 2016 18:09:53 +0100 Luis de Bethencourt <luisbg@osg.samsung.com> wrote:
> 
>> 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@osg.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.
> 
> It would be good if we can do this.
> 
> What is it in kernel.h that requires dynamic_debug.h?  I tried your
> patch along with
> 
> --- a/kernel/module.c~dynamic_debug-only-add-header-when-used-fix
> +++ a/kernel/module.c
> @@ -60,7 +60,6 @@
>  #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"
>  
> and module.o builds OK.
> 

Hi Andrew,

Thanks for looking at this so quickly.

The kbuild test robot has replied with one driver that needs to be changed
as well for this to work.

Will send a v2 in the next few hours.

Thanks,
Luis

Re: [RFC PATCH] dynamic_debug: only add header when used

[Luis de Bethencourt]

On 13/07/16 21:32, Andrew Morton wrote:
> On Wed, 13 Jul 2016 18:09:53 +0100 Luis de Bethencourt <luisbg@osg.samsung.com> wrote:
> 
>> 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@osg.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.
> 
> It would be good if we can do this.
> 
> What is it in kernel.h that requires dynamic_debug.h?  I tried your
> patch along with
> 
> --- a/kernel/module.c~dynamic_debug-only-add-header-when-used-fix
> +++ a/kernel/module.c
> @@ -60,7 +60,6 @@
>  #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"
>  
> and module.o builds OK.
> 

Hi Andrew,

Replying to why dynamic_debug.h is needed in module.c, which I didn't explain
before since I wanted to double-check.

kernel/module.c only needs dynamic_debug.h when CONFIG_DYNAMIC_DEBUG is not
set. Which is probably why you could build it in your side.
 
If you deactivate that config you get an error in the two uses of
ddebug_remove_module and one for ddebug_dyndbg_module_param_cb().

For example:
------------------------------------------------------
kernel/module.c: In function ‘free_module’:
kernel/module.c:2080:2: error: implicit declaration of function ‘ddebug_remove_module’
[-Werror=implicit-function-declaration]
  ddebug_remove_module(mod->name);
------------------------------------------------------

By the way, since you added my patch in your -mm tree I resent with you listed
as Signed-off-by, I hope that is OK. Let me know if it isn't for the future. 

Thanks :)
Luis