linux-kernel - Re: [PATCH v5 1/5] bug/kunit: Core support for suppressing warning backtraces

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Message-ID: <20250529090129.GZ24938@noisy.programming.kicks-ass.net>
Date: Thu, 29 May 2025 11:01:29 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Alessandro Carminati <acarmina@...hat.com>
Cc: linux-kselftest@...r.kernel.org,
	Dan Carpenter <dan.carpenter@...aro.org>,
	Kees Cook <keescook@...omium.org>,
	Daniel Diaz <daniel.diaz@...aro.org>,
	David Gow <davidgow@...gle.com>,
	Arthur Grillo <arthurgrillo@...eup.net>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	Naresh Kamboju <naresh.kamboju@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Maxime Ripard <mripard@...nel.org>,
	Ville Syrjala <ville.syrjala@...ux.intel.com>,
	Daniel Vetter <daniel@...ll.ch>, Guenter Roeck <linux@...ck-us.net>,
	Alessandro Carminati <alessandro.carminati@...il.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Jeff Johnson <jeff.johnson@....qualcomm.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Shuah Khan <skhan@...uxfoundation.org>,
	Linux Kernel Functional Testing <lkft@...aro.org>,
	dri-devel@...ts.freedesktop.org, kunit-dev@...glegroups.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/5] bug/kunit: Core support for suppressing warning
 backtraces

On Mon, May 26, 2025 at 01:27:51PM +0000, Alessandro Carminati wrote:

>  #define __WARN()		__WARN_FLAGS(BUGFLAG_TAINT(TAINT_WARN))
>  #define __WARN_printf(taint, arg...) do {				\
> -		instrumentation_begin();				\
> -		__warn_printk(arg);					\
> -		__WARN_FLAGS(BUGFLAG_NO_CUT_HERE | BUGFLAG_TAINT(taint));\
> -		instrumentation_end();					\
> +		if (!KUNIT_IS_SUPPRESSED_WARNING(__func__)) {		\
> +			instrumentation_begin();			\
> +			__warn_printk(arg);				\
> +			__WARN_FLAGS(BUGFLAG_NO_CUT_HERE |		\
> +				BUGFLAG_TAINT(taint));			\
> +			instrumentation_end();				\
> +		}							\
>  	} while (0)
>  #define WARN_ON_ONCE(condition) ({				\
>  	int __ret_warn_on = !!(condition);			\
> -	if (unlikely(__ret_warn_on))				\
> +	if (unlikely(__ret_warn_on) && !KUNIT_IS_SUPPRESSED_WARNING(__func__))	\
>  		__WARN_FLAGS(BUGFLAG_ONCE |			\
>  			     BUGFLAG_TAINT(TAINT_WARN));	\
>  	unlikely(__ret_warn_on);				\
> @@ -121,7 +130,7 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
>  #ifndef WARN_ON
>  #define WARN_ON(condition) ({						\
>  	int __ret_warn_on = !!(condition);				\
> -	if (unlikely(__ret_warn_on))					\
> +	if (unlikely(__ret_warn_on) && !KUNIT_IS_SUPPRESSED_WARNING(__func__))	\
>  		__WARN();						\
>  	unlikely(__ret_warn_on);					\
>  })
> @@ -138,7 +147,7 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
>  
>  #define WARN_TAINT(condition, taint, format...) ({			\
>  	int __ret_warn_on = !!(condition);				\
> -	if (unlikely(__ret_warn_on))					\
> +	if (unlikely(__ret_warn_on) && !KUNIT_IS_SUPPRESSED_WARNING(__func__))	\
>  		__WARN_printf(taint, format);				\
>  	unlikely(__ret_warn_on);					\
>  })
> @@ -157,8 +166,10 @@ extern __printf(1, 2) void __warn_printk(const char *fmt, ...);
>  #else /* !CONFIG_BUG */
>  #ifndef HAVE_ARCH_BUG
>  #define BUG() do {		\
> -	do {} while (1);	\
> -	unreachable();		\
> +	if (!KUNIT_IS_SUPPRESSED_WARNING(__func__)) {			\
> +		do {} while (1);					\
> +		unreachable();						\
> +	}								\
>  } while (0)
>  #endif

NAK

This is again doing it wrong -- this will bloat every frigging bug/warn
site for no reason. 

Like I said before; you need to do this on the report_bug() size of
things.