linux-kernel - Re: [PATCH] printk: rename vprintk

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Date:   Tue, 30 Mar 2021 16:33:25 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] printk: rename vprintk_func to vprintk

On Tue 2021-03-30 14:59:31, John Ogness wrote:
> On 2021-03-30, Petr Mladek <pmladek@...e.com> wrote:
> > On Tue 2021-03-23 15:42:01, Rasmus Villemoes wrote:
> >> The printk code is already hard enough to understand. Remove an
> >> unnecessary indirection by renaming vprintk_func to vprintk (adding
> >> the asmlinkage annotation), and removing the vprintk definition from
> >> printk.c. That way, printk is implemented in terms of vprintk as one
> >> would expect, and there's no "vprintk_func, what's that? Some function
> >> pointer that gets set where?"
> >> 
> >> The declaration of vprintk in linux/printk.h already has the
> >> __printf(1,0) attribute, there's no point repeating that with the
> >> definition - it's for diagnostics in callers.
> >> 
> >> linux/printk.h already contains a static inline {return 0;} definition
> >> of vprintk when !CONFIG_PRINTK.
> >> 
> >> Since the corresponding stub definition of vprintk_func was not marked
> >> "static inline", any translation unit including internal.h would get a
> >> definition of vprintk_func - it just so happens that for
> >> !CONFIG_PRINTK, there is precisely one such TU, namely printk.c. Had
> >> there been more, it would be a link error; now it's just a silly waste
> >> of a few bytes of .text, which one must assume are rather precious to
> >> anyone disabling PRINTK.
> >> 
> >> $ objdump -dr kernel/printk/printk.o
> >> 00000330 <vprintk_func>:
> >>  330:   31 c0                   xor    %eax,%eax
> >>  332:   c3                      ret
> >>  333:   8d b4 26 00 00 00 00    lea    0x0(%esi,%eiz,1),%esi
> >>  33a:   8d b6 00 00 00 00       lea    0x0(%esi),%esi
> >> 
> >> Signed-off-by: Rasmus Villemoes <linux@...musvillemoes.dk>
> >
> > Nice clean up!
> >
> > Reviewed-by: Petr Mladek <pmladek@...e.com>
> >
> > John,
> >
> > it conflicts with the patchset removing printk safe buffers[1].
> > Would you prefer to queue this into the patchset?
> > Or should I push it into printk/linux.git, printk-rework and you would
> > base v2 on top of it?
> 
> Please push it to printk-rework. I will base my v2 on top of it.

The patch is committed in printk/linux.git, branch printk-rework.
It is queued for 5.13.

Best Regards,
Petr