linux-kernel - Re: [PATCH] therm_throt.c: Fix error handling in thermal_throttle_add

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Message-ID: <20100903093553.GA6821@elte.hu>
Date:	Fri, 3 Sep 2010 11:35:53 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	H Peter Anvin <hpa@...or.com>, Len Brown <lenb@...nel.org>,
	Jin Dongming <jin.dongming@...css.fujitsu.com>,
	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>,
	Jean Delvare <khali@...ux-fr.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	lm-sensors <lm-sensors@...sensors.org>
Subject: Re: [PATCH] therm_throt.c: Fix error handling in
 thermal_throttle_add_dev

* Fenghua Yu <fenghua.yu@...el.com> wrote:

> From: Fenghua Yu <fenghua.yu@...el.com>
> 
> Warn when sysfs_add_file_to_group fails.
> 
> Also add missing curly braces.
> 
> Signed-off-by: Fenghua Yu <fenghua.yu@...el.com>
> ---
>  arch/x86/kernel/cpu/mcheck/therm_throt.c |   14 ++++++++++----
>  1 files changed, 10 insertions(+), 4 deletions(-)

> +               WARN_ON(err);

Hm, we tend to use WARN_ON_ONCE(), to avoid repeat spamming of the 
syslog. Also, and perhaps more importantly, WARN_ON() is not a 
particularly smart way to handle errors. How do other drivers handle 
sysfs registration failures?

Also, that's not the only thing the patch does:

> @@ -211,20 +211,26 @@ static __cpuinit int thermal_throttle_add_dev(struct sys_device *sys_dev)

> -	return err;
> +	return 0;

How is the ignoring of an error and turning it into a WARN_ON() a fix? 
Either it makes no sense to return errors - in which case the whole 
add_dev method needs to be fixed in all drivers - or it makes sense, in 
which case the behavior here is inconsistent.

At minimum more explanation is needed in the changelog.

Thanks,

	Ingo
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