linux-kernel - Re: [PATCH] opp: Prepare for ->set_opp() helper to work without regulators

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Date:   Tue, 19 Jan 2021 20:16:11 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] opp: Prepare for ->set_opp() helper to work without
 regulators

19.01.2021 09:35, Viresh Kumar пишет:
> +	mutex_lock(&opp_table->lock);
> +	opp_table->set_opp_data = data;
> +	if (opp_table->sod_supplies) {
> +		data->old_opp.supplies = opp_table->sod_supplies;
> +		data->new_opp.supplies = opp_table->sod_supplies +
> +					 opp_table->regulator_count;
> +	}
> +	mutex_unlock(&opp_table->lock);

Why do we need all these locks in this patch?

The OPP API isn't thread-safe, these locks won't make the API
thread-safe. At least both sod_supplies and set_opp() pointers should be
set and unset under the lock.

If you're about to make OPP thread-safe, then I suggest to do it
separately from this change. Otherwise this patch looks good to me.