linux-kernel - Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into printk(KERN

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Message-ID: <a4f8cfc41d4b7f9f76a403767cfc28d5ffafc1ee.camel@perches.com>
Date:   Thu, 28 May 2020 10:08:18 -0700
From:   Joe Perches <joe@...ches.com>
To:     Petr Mladek <pmladek@...e.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Dmitry Vyukov <dvyukov@...gle.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] twist: allow converting pr_devel()/pr_debug() into
 printk(KERN_DEBUG)

On Thu, 2020-05-28 at 14:14 +0200, Petr Mladek wrote:
> On Thu 2020-05-28 20:33:10, Tetsuo Handa wrote:
> > On 2020/05/28 19:59, Petr Mladek wrote:
> > > 2. Add twist into vprintk_store(). In the current, implementation
> > >    it would do:
> > > 
> > >   #if TWIST
> > > 	return text_len;
> > >   #endif
> > > 
> > > 	return log_output(facility, level, lflags,
> > > 			  dict, dictlen, text, text_len);
> > 
> > This part could be possible. But
> > 
> > > 1. Add twist into ddebug_add_module() and enable all newly added
> > >    entries by default. For example, by calling
> > >    ddebug_exec_query("*:+p", const char *modname) or what is the syntax.
> > > 
> > >    This will cause that any pr_devel() variant will always get called.
> > 
> > how to handle
> > 
> > > >   #define no_printk(fmt, ...)                             \
> > > >   ({                                                      \
> > > >           if (0)                                          \
> > > >                   printk(fmt, ##__VA_ARGS__);             \
> > > >           0;                                              \
> > > >   })
> > 
> > part used by e.g. pr_devel() ? Since this macro is not using dynamic debug
> > interface, vprintk_store() will not be called from the beginning. Are you
> > suggesting that we should convert no_printk() to use dynamic debug interface ?
> 
> OK, this is one more path that would need special handling. Two paths
> are much better than 15.

A few more:

$ grep-2.5.4 --include=*.[ch] -rP '\if\s*\(\s*0\s*\)\s*\{?\s*\\?\s*no_printk' *
drivers/platform/x86/thinkpad_acpi.c:	do { if (0) no_printk(format, ##arg); } while (0)
fs/ntfs/debug.h:	if (0)								\
		no_printk(fmt, ##__VA_ARGS__);				\
include/linux/net.h:		if (0)						\
			no_printk(KERN_DEBUG pr_fmt(fmt), ##__VA_ARGS__); \
kernel/cred.c:	if (0)								\
		no_printk("[%-5.5s%5u] " FMT "\n",			\