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Date: Sat, 28 Dec 2013 12:08:15 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Joe Perches <joe@perches.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
        Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
        Jiri Kosina <jkosina@suse.cz>, Al Viro <viro@zeniv.linux.org.uk>,
        "David S. Miller" <davem@davemloft.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier
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On Sat, 28 Dec 2013 11:53:25 -0800 Joe Perches <joe@perches.com> wrote:

> > > #define PRINTK_PID      "\002"
> > > #define PRINTK_TASK_ID  "\003"  /* "comm:pid" */
> > >
> > >         printk(PRINTK_TASK_ID ": hair on fire\n");
> > >
> > > It's certainly compact.  I doubt if there's any existing code which
> > > deliberately prints control chars?
> > 
> > But the rest looks OK to me.
> 
> Tell me again, what's wrong with using p or current?
> 
> printk("%pt", current);

Nothing much.  It's just that all these callsites are generating the
code to pass an argument which the callee already has access to. 
Optimizing that will reduce text size a bit.

There's also the matter of providing a standard and abstracted way of
representing a task, instead of directly accessing its ->comm.  But
that's a separate thing from new printk tokens.