On Tue, 25 Aug 2015 09:53:51 -0700 Joe Perches <[email protected]> wrote:
> commit e0e817392b9a ("CRED: Add some configurable debugging [try #6]")
> added the kdebug mechanism to this file back in 2009.
>
> The kdebug macro calls no_printk which always evaluates arguments.
>
> Most of the kdebug uses have an unnecessary call of
> atomic_read(&cred->usage)
>
> Make the kdebug macro do nothing by defining it with
> do { if (0) no_printk(...); } while (0)
> when not enabled.
>
> $ size kernel/cred.o* (defconfig x86-64)
> text data bss dec hex filename
> 2748 336 8 3092 c14 kernel/cred.o.new
> 2788 336 8 3132 c3c kernel/cred.o.old
>
> Miscellanea:
> o Neaten the #define kdebug macros while there
>
> ...
>
> --- a/kernel/cred.c
> +++ b/kernel/cred.c
> @@ -20,11 +20,16 @@
> #include <linux/cn_proc.h>
>
> #if 0
> -#define kdebug(FMT, ...) \
> - printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid
> ,##__VA_ARGS__)
> +#define kdebug(FMT, ...) \
> + printk("[%-5.5s%5u] " FMT "\n", \
> + current->comm, current->pid, ##__VA_ARGS__)
> #else
> -#define kdebug(FMT, ...) \
> - no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid
> ,##__VA_ARGS__)
> +#define kdebug(FMT, ...) \
> +do { \
> + if (0) \
> + no_printk("[%-5.5s%5u] " FMT "\n", \
> + current->comm, current->pid, ##__VA_ARGS__); \
> +} while (0)
> #endif
>
> static struct kmem_cache *cred_jar;
Did you consider doing this within no_printk()? That would break code
which is relying on side-effects in the evaluation of a printk arg but
that's pretty weird and I bet there isn't (and won't be) such code.
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