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

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Message-ID: <20100905123229.GA8254@elte.hu>
Date:	Sun, 5 Sep 2010 14:32:29 +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:

> Or other options could be:
> 
> 1. Just calling sysfs_add_file_to_group() without collecting returned error and
> return 0 at the end (driver/pci/pcie/aspm.c does like this). The drawback is
> there is no error logged if an unlikely errorr occurs. But user can see some
> files are missing in sysfs.
>
> 2. Or collect errors in err1, err2, etc for each sysfs_add_file_to_group. At
> the end, return -ENODEV(??) if any err1, err2, etc is not 0. This option makes
> code unreasonable complex to handle unlikely errors.

Well, the usual way to handle errors is to abort the operation when it 
occurs, and return the error code that sysfs_add_file_to_group() gave.

The error is not 'fatal' but missing sysfs files sure are confusing, and 
might break user-land which depends on them. So we should either 
initialize a driver fully - or not intialize it at all.

Now, a sub-case is the question whether to emit something more than the 
return code from sysfs_add_file_to_group(). If it's exceedingly rare 
(and subsequently poorly tested) then adding a WARN_ON_ONCE(ret) is OK - 
but that error code should be returned.

Am i missing any detail?

Thanks,

	Ingo
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