Re: [lm-sensors] [patch 1/5] hwmon: Convert fschmd to unlocked_ioctl

From: Hans de Goede
Date: Fri Nov 06 2009 - 08:35:09 EST


On 11/06/2009 02:22 PM, Arnd Bergmann wrote:
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.

Moving the ident struct to the data structure would have it needlessly
using RAM all the time, the best and simplest fix for this is to simply
stop declaring ident static inside the ioctl function.


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