linux-kernel - Re: [PATCH 12/12] PM / OPP: Update Documentation to remove RCU specific bits

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Date:   Mon, 9 Jan 2017 14:39:37 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Rafael Wysocki <rjw@...ysocki.net>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Len Brown <len.brown@...el.com>, Pavel Machek <pavel@....cz>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH 12/12] PM / OPP: Update Documentation to remove RCU
 specific bits

On 12/07, Viresh Kumar wrote:
> @@ -137,15 +121,18 @@ functions return the matching pointer representing the opp if a match is
>  found, else returns error. These errors are expected to be handled by standard
>  error checks such as IS_ERR() and appropriate actions taken by the caller.
>  
> +Callers of these functions shall call dev_pm_opp_put() after they have used the
> +OPP. Otherwise the memory for the OPP will never get freed and result in
> +memleak.
> +
>  dev_pm_opp_find_freq_exact - Search for an OPP based on an *exact* frequency and
>  	availability. This function is especially useful to enable an OPP which
>  	is not available by default.
>  	Example: In a case when SoC framework detects a situation where a
>  	higher frequency could be made available, it can use this function to
>  	find the OPP prior to call the dev_pm_opp_enable to actually make it available.
> -	 rcu_read_lock();
>  	 opp = dev_pm_opp_find_freq_exact(dev, 1000000000, false);
> -	 rcu_read_unlock();
> +	 dev_pm_opp_put(opp);
>  	 /* dont operate on the pointer.. just do a sanity check.. */
>  	 if (IS_ERR(opp)) {
>  		pr_err("frequency not disabled!\n");
> @@ -163,9 +150,8 @@ dev_pm_opp_find_freq_floor - Search for an available OPP which is *at most* the
>  	frequency.
>  	Example: To find the highest opp for a device:
>  	 freq = ULONG_MAX;
> -	 rcu_read_lock();
>  	 dev_pm_opp_find_freq_floor(dev, &freq);
> -	 rcu_read_unlock();
> +	 dev_pm_opp_put(opp);

opp doesn't exist in the scope here. Missing an assignment during
the dev_pm_opp_find_freq_floor() call?

-- 
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