Re: [RFC PATCH] printk: Convert pr_<level> macros to functions

From: Joe Perches
Date: Thu Mar 04 2010 - 16:29:58 EST

On Thu, 2010-03-04 at 12:49 -0800, Andrew Morton wrote:
> On Wed, 03 Mar 2010 07:20:18 -0800 Joe Perches <joe@xxxxxxxxxxx> wrote:
> > Maybe moving printed_len to file scope is racy somehow?
> Yes, printed_len will get corrupted when multiple CPU's are running
> printk/vprintk simultaneously. That'll need to be fixed.

I think it'll be easier to use the %pV construct that
I posted today:

> Is it possible to reduce the amount of
> code movement in the patch, make it a bit easier to follow?

I can do the move-around separately.

I think it'll be better as:

asmlinkage int pr_emerg(const char *fmt, ...)
struct va_format vaf;
va_list args;

va_start(args, fmt);
vaf.fmt = fmt; = &args;
r = printk(KERN_EMERG "%pV", &vaf);

return r;

I believe that avoids any racing.

> I think it would be justifiable to cook up a freaky macro and expand it
> eight times to avoid this duplication. Ugly, but better than lots of
> duplication.

Maybe something like:

#define define_pr_level(function, level) \
asmlinkage int function(const char *fmt, ...) \
{ \
struct va_format vaf; \
va_list args; \
va_start(args, fmt); \
vaf.fmt = fmt; \ = &args; \
r = printk(level "%pV", &vaf); \
va_end(args); \
return r; \
} \

define_pr_level(pr_emerg, KERN_EMERG);
define_pr_level(pr_alert, KERN_ALERT);
define_pr_level(pr_crit, KERN_CRIT);
define_pr_level(pr_err, KERN_ERR);
define_pr_level(pr_warning, KERN_WARNING);
define_pr_level(pr_notice, KERN_NOTICE);
define_pr_level(pr_info, KERN_INFO);

I think that's a bit ugly though myself.

> Or perhaps we can do it via a helper function which takes the
> additional argument?
> asmlinkage int pr_everything(char levelchar, const char *fmt, ...)

I believe that could not work.
The symbol names to link against wouldn't be found.

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