linux-kernel - Re: [PATCH 06/12] PM / OPP: Add 'struct kref' to struct dev_pm

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Message-ID: <20170113085639.GE9953@vireshk-i7>
Date:   Fri, 13 Jan 2017 14:26:39 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH 06/12] PM / OPP: Add 'struct kref' to struct dev_pm_opp

On 13-01-17, 00:52, Stephen Boyd wrote:
> What still doesn't make sense is how an individual OPP could go
> away without the table that the OPP lives in also going away.

dev_pm_opp_remove() is one such option, which can remove OPPs
individually. Over that, while remove tables we remove all the OPPs
one by one. So that really does happen.

> If
> an OPP is going away while a driver has a reference to it, then
> the driver using that OPP should probably not be using it.

That is being protected with this patch now and the drivers can use
them freely.

> TL;DR
> letting drivers use OPP pointers outside of the OPP core feels
> racy.

Hmm, we don't update the OPP a lot after creating it today. But that's
a different problem to solve, if we really see a race there.

-- 
viresh