On Fri, 2016-06-24 at 10:30 +0200, Borislav Petkov wrote:
> From: Borislav Petkov <b...@suse.de>
>
> Have printk*once() return a bool which denotes whether the string was
> printed or not so that calling code can react accordingly.
I expected object size to either increase or stay the
same with just this change.
Oddly, at least with gcc 5.3, some defconfig x86-64
objects _decrease_ in size.
for example: drivers/gpu/drm/i915/intel_opregion.o
I presume there's some curiosity in the gcc optimizer
with the evaluation of statement expression macros that
don't return a value.
Perhaps the printk_once macros should end with
unlikely(__ret_print_once);
like the WARN_ONCE variants.
> Signed-off-by: Borislav Petkov <b...@suse.de>
> Cc: Andrew Morton <a...@linux-foundation.org>
> ---
> include/linux/printk.h | 17 ++++++++++++-----
> 1 file changed, 12 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index f4da695fd615..464fcdddb359 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -108,11 +108,14 @@ struct va_format {
> * Dummy printk for disabled debugging statements to use whilst maintaining
> * gcc's format checking.
> */
> -#define no_printk(fmt, ...) \
> -do { \
> - if (0) \
> - printk(fmt, ##__VA_ARGS__); \
> -} while (0)
> +#define no_printk(fmt, ...) \
> +({ \
> + do { \
> + if (0) \
> + printk(fmt, ##__VA_ARGS__); \
> + } while (0); \
> + 0; \
> +})
>
> #ifdef CONFIG_EARLY_PRINTK
> extern asmlinkage __printf(1, 2)
> @@ -309,20 +312,24 @@ extern asmlinkage void dump_stack(void) __cold;
> #define printk_once(fmt, ...) \
> ({ \
> static bool __print_once __read_mostly; \
> + bool __ret_print_once = !__print_once; \
> \
> if (!__print_once) { \
> __print_once = true; \
> printk(fmt, ##__VA_ARGS__); \
> } \
> + __ret_print_once; \
> })
> #define printk_deferred_once(fmt, ...) \
> ({ \
> static bool __print_once __read_mostly; \
> + bool __ret_print_once = !__print_once; \
> \
> if (!__print_once) { \
> __print_once = true; \
> printk_deferred(fmt, ##__VA_ARGS__); \
> } \
> + __ret_print_once; \
> })
> #else
> #define printk_once(fmt, ...) \
