linux-kernel - Re: [lm-sensors] [patch 1/5] hwmon: Convert fschmd to unlocked

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Message-Id: <200911061422.49596.arnd@arndb.de>
Date:	Fri, 6 Nov 2009 14:22:49 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Jean Delvare <khali@...ux-fr.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>, lm-sensors@...sensors.org,
	Hans de Goede <hdegoede@...hat.com>
Subject: Re: [lm-sensors] [patch 1/5] hwmon: Convert fschmd to unlocked_ioctl

On Friday 06 November 2009, Jean Delvare wrote:
> I'm not sure why we need to hold the mutex here? My understanding is
> that watchdog_data_mutex protects watchdog_data_list and each
> watchdog's kref. And the above code doesn't touch either.
> 
> What I am more worried about is why ident is declared static. This
> looks like a bug to me. Instead of abusing watchdog_data_mutex to
> workaround this, I'd rather remove the "static". I guess that the
> current code happens to work because neither data->revision nor
> nowayout can change over time, but this looks needlessly fragile.
> 
> Hans, any comment?

The data copied into the watchdog_info data structure is completely
static. To make that clearer, I'd suggest moving it outside of
the ioctl function, and initializing it from fschmd_init.
Then it becomes obvious that the mutex is not needed to protect it.

	Arnd <><
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