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Date: Wed, 07 Dec 2016 22:23:53 +0900
From: Chanwoo Choi <cw00.choi@...sung.com>
To: Viresh Kumar <viresh.kumar@...aro.org>,
Rafael Wysocki <rjw@...ysocki.net>,
Kevin Hilman <khilman@...nel.org>,
Tony Lindgren <tony@...mide.com>,
Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
Stephen Boyd <sboyd@...eaurora.org>,
Peter De Schrijver <pdeschrijver@...dia.com>,
Prashant Gaikwad <pgaikwad@...dia.com>,
Stephen Warren <swarren@...dotorg.org>,
Thierry Reding <thierry.reding@...il.com>,
Alexandre Courbot <gnurou@...il.com>,
Kukjin Kim <kgene@...nel.org>,
Krzysztof Kozlowski <krzk@...nel.org>,
Javier Martinez Canillas <javier@....samsung.com>,
MyungJoo Ham <myungjoo.ham@...sung.com>,
Kyungmin Park <kyungmin.park@...sung.com>,
Amit Daniel Kachhap <amit.kachhap@...il.com>,
Javi Merino <javi.merino@...nel.org>,
Zhang Rui <rui.zhang@...el.com>,
Eduardo Valentin <edubezval@...il.com>
Cc: linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Vincent Guittot <vincent.guittot@...aro.org>
Subject: Re: [PATCH 07/12] PM / OPP: Update OPP users to put reference
Hi Viresh,
[snip]
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index b0de42972b74..89add0d7c017 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -111,18 +111,16 @@ static void devfreq_set_freq_table(struct devfreq *devfreq)
> return;
> }
>
> - rcu_read_lock();
> for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
> opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
> + dev_pm_opp_put(opp);
I think that the dev_pm_opp_put(opp) should be called after if statement
If dev_pm_opp_find_freq_ceil() return error, I think the calling of
dev_pm_opp_put(opp) is not necessary.
> if (IS_ERR(opp)) {
> devm_kfree(devfreq->dev.parent, profile->freq_table);
> profile->max_state = 0;
> - rcu_read_unlock();
> return;
> }
> profile->freq_table[i] = freq;
> }
> - rcu_read_unlock();
> }
>
> /**
> @@ -1107,9 +1105,9 @@ static ssize_t available_frequencies_show(struct device *d,
> ssize_t count = 0;
> unsigned long freq = 0;
>
> - rcu_read_lock();
> do {
> opp = dev_pm_opp_find_freq_ceil(dev, &freq);
> + dev_pm_opp_put(opp);
ditto.
> if (IS_ERR(opp))
> break;
>
> @@ -1117,7 +1115,6 @@ static ssize_t available_frequencies_show(struct device *d,
> "%lu ", freq);
> freq++;
> } while (1);
> - rcu_read_unlock();
>
> /* Truncate the trailing space */
> if (count)
> @@ -1219,11 +1216,8 @@ subsys_initcall(devfreq_init);
> * @freq: The frequency given to target function
> * @flags: Flags handed from devfreq framework.
> *
> - * Locking: This function must be called under rcu_read_lock(). opp is a rcu
> - * protected pointer. The reason for the same is that the opp pointer which is
> - * returned will remain valid for use with opp_get_{voltage, freq} only while
> - * under the locked area. The pointer returned must be used prior to unlocking
> - * with rcu_read_unlock() to maintain the integrity of the pointer.
> + * The callers are required to call dev_pm_opp_put() for the returned OPP after
> + * use.
> */
> struct dev_pm_opp *devfreq_recommended_opp(struct device *dev,
> unsigned long *freq,
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index a8ed7792ece2..49ce38cef460 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -103,18 +103,17 @@ static int exynos_bus_target(struct device *dev, unsigned long *freq, u32 flags)
> int ret = 0;
>
> /* Get new opp-bus instance according to new bus clock */
> - rcu_read_lock();
> new_opp = devfreq_recommended_opp(dev, freq, flags);
> if (IS_ERR(new_opp)) {
> dev_err(dev, "failed to get recommended opp instance\n");
> - rcu_read_unlock();
> return PTR_ERR(new_opp);
> }
>
> new_freq = dev_pm_opp_get_freq(new_opp);
> new_volt = dev_pm_opp_get_voltage(new_opp);
> + dev_pm_opp_put(new_opp);
> +
> old_freq = bus->curr_freq;
> - rcu_read_unlock();
>
> if (old_freq == new_freq)
> return 0;
> @@ -214,17 +213,16 @@ static int exynos_bus_passive_target(struct device *dev, unsigned long *freq,
> int ret = 0;
>
> /* Get new opp-bus instance according to new bus clock */
> - rcu_read_lock();
> new_opp = devfreq_recommended_opp(dev, freq, flags);
> if (IS_ERR(new_opp)) {
> dev_err(dev, "failed to get recommended opp instance\n");
> - rcu_read_unlock();
> return PTR_ERR(new_opp);
> }
>
> new_freq = dev_pm_opp_get_freq(new_opp);
> + dev_pm_opp_put(new_opp);
> +
> old_freq = bus->curr_freq;
> - rcu_read_unlock();
>
> if (old_freq == new_freq)
> return 0;
> @@ -358,16 +356,14 @@ static int exynos_bus_parse_of(struct device_node *np,
>
> rate = clk_get_rate(bus->clk);
>
> - rcu_read_lock();
> opp = devfreq_recommended_opp(dev, &rate, 0);
> if (IS_ERR(opp)) {
> dev_err(dev, "failed to find dev_pm_opp\n");
> - rcu_read_unlock();
> ret = PTR_ERR(opp);
> goto err_opp;
> }
> bus->curr_freq = dev_pm_opp_get_freq(opp);
> - rcu_read_unlock();
> + dev_pm_opp_put(opp);
>
> return 0;
>
> diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> index 9ef46e2592c4..671a1e0afc6e 100644
> --- a/drivers/devfreq/governor_passive.c
> +++ b/drivers/devfreq/governor_passive.c
> @@ -59,9 +59,9 @@ static int devfreq_passive_get_target_freq(struct devfreq *devfreq,
> * list of parent device. Because in this case, *freq is temporary
> * value which is decided by ondemand governor.
> */
> - rcu_read_lock();
> opp = devfreq_recommended_opp(parent_devfreq->dev.parent, freq, 0);
> - rcu_read_unlock();
> + dev_pm_opp_put(opp);
ditto.
> +
> if (IS_ERR(opp)) {
> ret = PTR_ERR(opp);
> goto out;
> diff --git a/drivers/devfreq/rk3399_dmc.c b/drivers/devfreq/rk3399_dmc.c
> index 27d2f349b53c..40a2499730fc 100644
> --- a/drivers/devfreq/rk3399_dmc.c
> +++ b/drivers/devfreq/rk3399_dmc.c
> @@ -91,17 +91,13 @@ static int rk3399_dmcfreq_target(struct device *dev, unsigned long *freq,
> unsigned long target_volt, target_rate;
> int err;
>
> - rcu_read_lock();
> opp = devfreq_recommended_opp(dev, freq, flags);
> - if (IS_ERR(opp)) {
> - rcu_read_unlock();
> + if (IS_ERR(opp))
> return PTR_ERR(opp);
> - }
>
> target_rate = dev_pm_opp_get_freq(opp);
> target_volt = dev_pm_opp_get_voltage(opp);
> -
> - rcu_read_unlock();
> + dev_pm_opp_put(opp);
>
> if (dmcfreq->rate == target_rate)
> return 0;
> @@ -422,15 +418,13 @@ static int rk3399_dmcfreq_probe(struct platform_device *pdev)
>
> data->rate = clk_get_rate(data->dmc_clk);
>
> - rcu_read_lock();
> opp = devfreq_recommended_opp(dev, &data->rate, 0);
> - if (IS_ERR(opp)) {
> - rcu_read_unlock();
> + if (IS_ERR(opp))
> return PTR_ERR(opp);
> - }
> +
> data->rate = dev_pm_opp_get_freq(opp);
> data->volt = dev_pm_opp_get_voltage(opp);
> - rcu_read_unlock();
> + dev_pm_opp_put(opp);
>
> rk3399_devfreq_dmc_profile.initial_freq = data->rate;
>
> diff --git a/drivers/devfreq/tegra-devfreq.c b/drivers/devfreq/tegra-devfreq.c
> index fe9dce0245bf..214fff96fa4a 100644
> --- a/drivers/devfreq/tegra-devfreq.c
> +++ b/drivers/devfreq/tegra-devfreq.c
> @@ -487,15 +487,13 @@ static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
> struct dev_pm_opp *opp;
> unsigned long rate = *freq * KHZ;
>
> - rcu_read_lock();
> opp = devfreq_recommended_opp(dev, &rate, flags);
> if (IS_ERR(opp)) {
> - rcu_read_unlock();
> dev_err(dev, "Failed to find opp for %lu KHz\n", *freq);
> return PTR_ERR(opp);
> }
> rate = dev_pm_opp_get_freq(opp);
> - rcu_read_unlock();
> + dev_pm_opp_put(opp);
>
> clk_set_min_rate(tegra->emc_clock, rate);
> clk_set_rate(tegra->emc_clock, 0);
[snip]
Best Regards,
Chanwoo Choi
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