linux-kernel - Re: clk: Per controller locks (prepare & enable)

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Date:	Tue, 5 Jul 2016 09:48:34 -0400
From:	Javier Martinez Canillas <javier@....samsung.com>
To:	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	Michael Turquette <mturquette@...libre.com>,
	Stephen Boyd <sboyd@...eaurora.org>, linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	Tomasz Figa <tomasz.figa@...il.com>,
	Sylwester Nawrocki <s.nawrocki@...sung.com>
Cc:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Andrzej Hajda <a.hajda@...sung.com>
Subject: Re: clk: Per controller locks (prepare & enable)

Hello Krzysztof,

On 07/05/2016 02:33 AM, Krzysztof Kozlowski wrote:
> On 07/04/2016 05:15 PM, Javier Martinez Canillas wrote:

[snip]

>>
>> Yes, splitting the lock per controller will fix the possible deadlock in
>> this case but I think we need an approach that is safe for all possible
>> scenarios. Otherwise it will work more by coincidence than due a design.
> 
> This is not a coincidence. This design is meant to fix this deadlock.
> Not by coincidence. By design.
>

Ok, if the configurations I described doesn't exist in practice and are
just theoretical then yes, doing a per controller lock is a good design. 
 
> You are talking about theoretical different configurations... without
> even real bug reports. I am providing an idea to fix a real deadlock and
> your argument is that it might not fix other (non-reported) deadlocks.
> These other deadlocks happen now as well probably...
>

I'm not against you re-working the locks to do it per controller, is just
that I thought it would be good to have a solution that is going to work
for all possible scenarios.

You asked for comments/opinions/ideas and I gave mine, that's all :)

> Best regards,
> Krzysztof
> 

Best regards,
-- 
Javier Martinez Canillas
Open Source Group
Samsung Research America