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From: Stephen Boyd <sboyd@codeaurora.org>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Rafael Wysocki <rjw@rjwysocki.net>,
	nm@ti.com, Viresh Kumar <vireshk@kernel.org>,
	linaro-kernel@lists.linaro.org, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Vincent Guittot <vincent.guittot@linaro.org>,
	robh@kernel.org, d-gerlach@ti.com, broonie@kernel.org
Subject: Re: [PATCH V2 2/8] PM / OPP: Don't use OPP structure outside of rcu protected section
Date: Mon, 24 Oct 2016 15:52:38 -0700	[thread overview]
Message-ID: <20161024225238.GR26139@codeaurora.org> (raw)
In-Reply-To: <7a0754e64236db2a977c6a6402c222fea6dc866d.1476952750.git.viresh.kumar@linaro.org>

On 10/20, Viresh Kumar wrote:
> The OPP structure must not be used out of the rcu protected section.
> Cache the values to be used in separate variables instead.
> 
> Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>

Was this found by visual inspection or through some static
checker? Just curious.

> @@ -633,6 +634,14 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
>  		return ret;
>  	}
>  
> +	if (IS_ERR(old_opp)) {
> +		old_u_volt = 0;
> +	} else {
> +		old_u_volt = old_opp->u_volt;
> +		old_u_volt_min = old_opp->u_volt_min;
> +		old_u_volt_max = old_opp->u_volt_max;
> +	}
> +
>  	u_volt = opp->u_volt;
>  	u_volt_min = opp->u_volt_min;
>  	u_volt_max = opp->u_volt_max;
> @@ -677,9 +686,10 @@ int dev_pm_opp_set_rate(struct device *dev, unsigned long target_freq)
>  			__func__, old_freq);
>  restore_voltage:
>  	/* This shouldn't harm even if the voltages weren't updated earlier */
> -	if (!IS_ERR(old_opp))
> -		_set_opp_voltage(dev, reg, old_opp->u_volt,
> -				 old_opp->u_volt_min, old_opp->u_volt_max);
> +	if (old_u_volt) {

What if old_u_volt == 0 is valid? We could have another variable
like 'valid' or something that we use to figure out if we should
set values instead. Then this isn't a potential pitfall.

> +		_set_opp_voltage(dev, reg, old_u_volt, old_u_volt_min,
> +				 old_u_volt_max);
> +	}
>  
>  	return ret;
>  }

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

  reply	other threads:[~2016-10-24 22:52 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-20  8:44 [PATCH V2 0/8] PM / OPP: Multiple regulator support Viresh Kumar
2016-10-20  8:44 ` [PATCH V2 1/8] PM / OPP: Reword binding supporting multiple regulators per device Viresh Kumar
2016-10-24 22:48   ` Stephen Boyd
2016-10-24 22:48     ` Stephen Boyd
2016-10-20  8:44 ` [PATCH V2 2/8] PM / OPP: Don't use OPP structure outside of rcu protected section Viresh Kumar
2016-10-24 22:52   ` Stephen Boyd [this message]
2016-10-25  3:37     ` Viresh Kumar
2016-10-20  8:44 ` [PATCH V2 3/8] PM / OPP: Manage supply's voltage/current in a separate structure Viresh Kumar
2016-10-20  8:44 ` [PATCH V2 4/8] PM / OPP: Pass struct dev_pm_opp_supply to _set_opp_voltage() Viresh Kumar
2016-10-24 23:14   ` Stephen Boyd
2016-10-25  3:45     ` Viresh Kumar
2016-10-25 20:26       ` Stephen Boyd
2016-10-26  3:34         ` Viresh Kumar
2016-10-20  8:44 ` [PATCH V2 5/8] PM / OPP: Add infrastructure to manage multiple regulators Viresh Kumar
2016-10-21 22:32   ` Dave Gerlach
2016-10-21 22:32     ` Dave Gerlach
2016-10-24  3:35     ` Viresh Kumar
2016-10-25 16:49   ` Stephen Boyd
2016-10-26  6:05     ` Viresh Kumar
2016-11-10  1:37       ` Stephen Boyd
2016-10-20  8:45 ` [PATCH V2 6/8] PM / OPP: Separate out _generic_opp_set_rate() Viresh Kumar
2016-10-25 18:59   ` Stephen Boyd
2016-10-26  6:07     ` Viresh Kumar
2016-10-20  8:45 ` [PATCH V2 7/8] PM / OPP: Allow platform specific custom opp_set_rate() callbacks Viresh Kumar
2016-10-25 19:01   ` Stephen Boyd
2016-10-26  6:07     ` Viresh Kumar
2016-10-20  8:45 ` [PATCH V2 8/8] PM / OPP: Don't WARN on multiple calls to dev_pm_opp_set_regulators() Viresh Kumar
2016-10-25 19:01   ` Stephen Boyd
2016-10-21 13:39 ` [PATCH V2 0/8] PM / OPP: Multiple regulator support Rafael J. Wysocki
2016-10-21 15:40   ` Viresh Kumar
2016-10-24  1:08     ` Dave Gerlach
2016-10-24  4:26       ` Viresh Kumar
2016-10-25 21:13         ` Dave Gerlach
2016-10-26  3:21           ` Viresh Kumar

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