linux-kernel - Re: [PATCH v13 3/6] clk: Make clk API return per-user struct clk instances

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Message-id: <54D3CD58.4030902@samsung.com>
Date:	Thu, 05 Feb 2015 21:06:48 +0100
From:	Sylwester Nawrocki <s.nawrocki@...sung.com>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-kernel@...r.kernel.org,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Javier Martinez Canillas <javier.martinez@...labora.co.uk>,
	Paul Walmsley <paul@...an.com>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	linux-omap@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v13 3/6] clk: Make clk API return per-user struct clk
 instances

On 05/02/15 20:44, Sylwester Nawrocki wrote:
>> +void __clk_put(struct clk *clk)
>> > +{
>> > +	if (!clk || WARN_ON_ONCE(IS_ERR(clk)))
>> > +		return;
>> > +
>> > +	clk_core_put(clk->core);
>> > +	kfree(clk);
>
> Why do we have kfree() here? clk_get() doesn't allocate the data structure 
> being freed here. What happens if we do clk_get(), clk_put(), clk_get() 
> on same clock?
> 
> I suspect __clk_free_clk() should be called in __clk_release() callback
> instead, but then there is an issue of safely getting reference to
> struct clk from struct clk_core pointer.

Please ignore this comment, I missed __clk_create_clk() calls in clkdev.c
Anyway, in current -next I'm seeing random pointer dereferences while
booting Odroid U3, I'll get back to debugging this tomorrow morning.

-- 
Regards,
Sylwester
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