linux-kernel - Re: [PATCH] DS2781 Maxim Stand-Alone Fuel Gauge battery and w1 slave drivers

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Message-ID: <20120229232457.GA12803@ioremap.net>
Date:	Thu, 1 Mar 2012 02:24:57 +0300
From:	Evgeniy Polyakov <zbr@...emap.net>
To:	Renata Sayakhova <rsayakhova@...il.com>
Cc:	linux-kernel@...r.kernel.org, greg@...ah.com
Subject: Re: [PATCH] DS2781 Maxim Stand-Alone Fuel Gauge battery and w1
 slave drivers

On Thu, Mar 01, 2012 at 12:17:30AM +0100, Renata Sayakhova (rsayakhova@...il.com) wrote:
> w1_process (w1.c line 982) holds mutex. If during w1_search_process (w1.c
> line 983) slave is found and battery initcall is already done at this
> moment than battery probe() is called. This call leads to
> power_supply_register() and device_add() which does among other things call
> battery properties. battery_get_property() should normally results in
> w1_ds2781_read() and w1_ds2781_io(), but w1_ds2781_io() calls itself
> mutex_lock.
> 
> So this weird function is a workaround to avoid a second mutex_lock during
> battery probe(). mutex_holder is set before power_supply_register() and
> unset when probe is done.
> 
> This is very brief, if it's not clear I'll try to explain in more details.
> I found this workaround in implementation of ds2780 battery and w1 slave
> drivers.

So basically IO routins caled from ->probe() are already locked so we
protect against deadlock. Ok, I see.

I have no objections, patch looks good
Greg, please pull it into your tree
Thank you

Acked-by: Evgeniy Polyakov <zbr@...emap.net>


-- 
	Evgeniy Polyakov
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