linux-kernel - Re: [PATCH 11/11 re-post] dynamic_debug: use a single printk() to emit msgs

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Date:	Mon, 18 Jul 2011 10:30:36 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Bart Van Assche <bvanassche@....org>, gregkh@...e.de,
	jim.cromie@...il.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/11 re-post] dynamic_debug: use a single printk() to
 emit msgs

On Fri, Jul 15, 2011 at 04:46:31PM -0700, Joe Perches wrote:
> On Fri, 2011-07-15 at 15:59 -0400, Jason Baron wrote:
> > here's Bart's suggestion as re-post. It looks much cleaner to
> > me...
> []
> > diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> []
> > @@ -422,52 +422,46 @@ static int ddebug_exec_query(char *query_string)
> >  	return 0;
> >  }
> >  
> > -static int dynamic_emit_prefix(const struct _ddebug *descriptor)
> > +#define PREFIX_SIZE 64
> > +#define LEFT(wrote) ((PREFIX_SIZE - wrote) > 0) ? (PREFIX_SIZE - wrote) : 0
> > +
> > +static char *dynamic_emit_prefix(const struct _ddebug *desc, char *buf)
> >  {
> > -	char tid[sizeof(int) + sizeof(int)/2 + 4];
> > -	char lineno[sizeof(int) + sizeof(int)/2];
> > +	int pos = 0;
> >  
> > -	if (descriptor->flags & _DPRINTK_FLAGS_INCL_TID) {
> > +	pos += snprintf(buf + pos, LEFT(pos), "%s", KERN_DEBUG);
> > +	if (desc->flags & _DPRINTK_FLAGS_INCL_TID) {
> >  		if (in_interrupt())
> > -			snprintf(tid, sizeof(tid), "%s", "<intr> ");
> > +			pos += snprintf(buf + pos, LEFT(pos), "%s ",
> > +						"<intr>");
> 
> scnprintf works without using LEFT.
> snprintf does as well.
> 
> http://lkml.org/lkml/2010/7/23/375
> 

So you're saying, just pass (PREFIX_SIZE - pos), as the second argument? I see
kernel code written both ways. I think it's fine as written, unless you feel
strongly about this.

thanks,

-Jason
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