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Subject: Re: [PATCH] kernel.h: Add a never optimized away pr_dbg for
 printk(KERN_DEBUG pr_fmt(fmt)...)
From: Joe Perches <joe@perches.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>
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	 <alpine.DEB.1.00.0910132031040.1244@chino.kir.corp.google.com>
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Date: Tue, 13 Oct 2009 21:21:49 -0700
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On Tue, 2009-10-13 at 20:34 -0700, David Rientjes wrote:
> On Tue, 13 Oct 2009, Joe Perches wrote:
> > Many developers use a logging message that
> > is printed at KERN_DEBUG level that is always
> > printed regardless of #define DEBUG levels.
> > pr_debug can be optimized away to a null statement.
> > Add a pr_dbg message that prints at KERN_DEBUG
> > level that uses pr_fmt() that can not be optimized
> > to nothing.
> pr_dbg() is horribly misnamed, it doesn't indicate why it exists vs. 
> pr_debug() at all.

Partially true, it's reasonably named because it's very short.

> Future users will undoubtedly use it by mistake when 
> they only really mean for the message to be emitted on DEBUG because 
> they've seen it in other places and haven't checked the implementation.

The cost of using pr_dbg instead of pr_debug isn't high.

The primary benefit is getting an automatic pr_fmt
and shorter code.

> I'd suggest pr_debug_force(), even though it's much longer (although still 
> shorter than printk(KERN_DEBUG)).

pr_dbg allows longer format strings without exceeding 80 chars.

printk(KERN_DEBUG
pr_debug_force
pr_dbg_always
pr_dbg_noopt

Other suggestions?