linux-kernel - Re: [PATCH] ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG

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Date:   Sun, 26 Sep 2021 11:51:05 +0100
From:   Chris Down <chris@...isdown.name>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-ia64@...r.kernel.org,
        Petr Mladek <pmladek@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tony Luck <tony.luck@...el.com>
Subject: Re: [PATCH] ia64: don't do IA64_CMPXCHG_DEBUG without CONFIG_PRINTK

Hi Randy,

Randy Dunlap writes:
>When CONFIG_PRINTK is not set, the CMPXCHG_BUGCHECK() macro calls
>_printk(), but _printk() is a static inline function, not available
>as an extern.
>Since the purpose of the macro is to print the BUGCHECK info,
>make this config option depend on PRINTK.
>
>Fixes multiple occurrences of this build error:
>
>../include/linux/printk.h:208:5: error: static declaration of '_printk' follows non-static declaration
>  208 | int _printk(const char *s, ...)
>      |     ^~~~~~~
>In file included from ../arch/ia64/include/asm/cmpxchg.h:5,
>../arch/ia64/include/uapi/asm/cmpxchg.h:146:28: note: previous declaration of '_printk' with type 'int(const char *, ...)'
>  146 |                 extern int _printk(const char *fmt, ...);
>
>Fixes: 337015573718 ("printk: Userspace format indexing support")

This Fixes tag doesn't make much sense. This was already broken long before 
that patch, just the error message changed: printk() was already static inline 
on !CONFIG_PRINTK for eons.

>Signed-off-by: Randy Dunlap <rdunlap@...radead.org>
>Cc: linux-ia64@...r.kernel.org
>Cc: Petr Mladek <pmladek@...e.com>
>Cc: Andrew Morton <akpm@...ux-foundation.org>
>Cc: Tony Luck <tony.luck@...el.com>
>Cc: Chris Down <chris@...isdown.name>
>---
> arch/ia64/Kconfig.debug |    2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
>--- linux-next-20210917.orig/arch/ia64/Kconfig.debug
>+++ linux-next-20210917/arch/ia64/Kconfig.debug
>@@ -39,7 +39,7 @@ config DISABLE_VHPT
>
> config IA64_DEBUG_CMPXCHG
> 	bool "Turn on compare-and-exchange bug checking (slow!)"
>-	depends on DEBUG_KERNEL
>+	depends on DEBUG_KERNEL && PRINTK
> 	help
> 	  Selecting this option turns on bug checking for the IA-64
> 	  compare-and-exchange instructions.  This is slow!  Itaniums