linux-kernel - Re: next-20221122: tinyconfig: ppc n s390: kernel/printk/printk.c:95:1: error: type specifier missing, defaults to 'int'; ISO C99 and later do not support implicit int [-Werror,-Wimplicit-int]

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Date:   Tue, 22 Nov 2022 16:55:26 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     John Ogness <john.ogness@...utronix.de>
Cc:     paulmck@...nel.org, Naresh Kamboju <naresh.kamboju@...aro.org>,
        open list <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Sergey Senozhatsky <senozhatsky@...omium.org>
Subject: Re: next-20221122: tinyconfig: ppc n s390:
 kernel/printk/printk.c:95:1: error: type specifier missing, defaults to
 'int'; ISO C99 and later do not support implicit int
 [-Werror,-Wimplicit-int]

On Tue 2022-11-22 16:33:39, John Ogness wrote:
> On 2022-11-22, "Paul E. McKenney" <paulmck@...nel.org> wrote:
> >> @paulmck: Do you have a problem with permanently activating CONFIG_SRCU?
> >
> > The people wanting it separate back in the day were those wanting very
> > tiny kernels.  I have not heard from them in a long time, so maybe it
> > is now OK to just make SRCU unconditional.
> 
> Who decides this? Or maybe I should create a semaphore-based Variant of
> console_srcu_read_lock()/console_srcu_read_unlock() for the
> "!CONFIG_PRINTK && !CONFIG_SRCU" case?

I would prefer to avoid it. It would require keeping this in mind.
Semaphore behaves very differently than srcu_read_lock (deadlocks,
nesting).

I am not sure how much the tiny SRCU would increase the size of
the kernel. I doubt that it would be more that what printk()
added by the various per-CPU and per-console buffers.

Well, another question is why we actually need to register the consoles
at all for !CONFIG_PRINTK. Only reasons come to my mind:

   + /dev/console
   + preventing double registration/unregistration (initialization)

I could imagine to handle these two use-cases a special way
on tiny systems. But I would do it only when anyone complains.

Best Regards,
Petr