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Commit 459ac375 authored by Javi Merino's avatar Javi Merino Committed by Eduardo Valentin
Browse files

thermal: cpu_cooling: don't call kcalloc() under rcu_read_lock 



build_dyn_power_table() allocates the power table while holding
rcu_read_lock.  kcalloc using GFP_KERNEL may sleep, so it can't be
called in an RCU read-side path.

Move the rcu protection to the part of the function that really needs
it: the part that handles the dev_pm_opp pointer received from
dev_pm_opp_find_freq_ceil().  In the unlikely case that there is an OPP
added to the cpu while this function is running, return -EAGAIN.

Fixes: c36cf071 ("thermal: cpu_cooling: implement the power cooling device API")
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: default avatarJavi Merino <javi.merino@arm.com>
Signed-off-by: default avatarEduardo Valentin <edubezval@gmail.com>
parent 0847e26a

drivers/thermal/cpu_cooling.c

+23 −24
Original line number Diff line number Diff line
@@ -262,7 +262,9 @@ static int cpufreq_thermal_notifier(struct notifier_block *nb, 
 * efficiently.  Power is stored in mW, frequency in KHz.  The

 * resulting table is in ascending order.

 *

 * Return: 0 on success, -E* on error.

 * Return: 0 on success, -EINVAL if there are no OPPs for any CPUs,

 * -ENOMEM if we run out of memory or -EAGAIN if an OPP was

 * added/enabled while the function was executing.

 */

static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device,

				 u32 capacitance)
@@ -270,11 +272,9 @@ static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device, 
	struct power_table *power_table;

	struct dev_pm_opp *opp;

	struct device *dev = NULL;

	int num_opps = 0, cpu, i, ret = 0;

	int num_opps = 0, cpu, i;

	unsigned long freq;



	rcu_read_lock();



	for_each_cpu(cpu, &cpufreq_device->allowed_cpus) {

		dev = get_cpu_device(cpu);

		if (!dev) {
@@ -284,24 +284,20 @@ static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device, 
		}



		num_opps = dev_pm_opp_get_opp_count(dev);

		if (num_opps > 0) {

		if (num_opps > 0)

			break;

		} else if (num_opps < 0) {

			ret = num_opps;

			goto unlock;

		}

		else if (num_opps < 0)

			return num_opps;

	}



	if (num_opps == 0) {

		ret = -EINVAL;

		goto unlock;

	}

	if (num_opps == 0)

		return -EINVAL;



	power_table = kcalloc(num_opps, sizeof(*power_table), GFP_KERNEL);

	if (!power_table) {

		ret = -ENOMEM;

		goto unlock;

	}

	if (!power_table)

		return -ENOMEM;



	rcu_read_lock();



	for (freq = 0, i = 0;

	     opp = dev_pm_opp_find_freq_ceil(dev, &freq), !IS_ERR(opp);
@@ -309,6 +305,11 @@ static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device, 
		u32 freq_mhz, voltage_mv;

		u64 power;



		if (i >= num_opps) {

			rcu_read_unlock();

			return -EAGAIN;

		}



		freq_mhz = freq / 1000000;

		voltage_mv = dev_pm_opp_get_voltage(opp) / 1000;
@@ -326,18 +327,16 @@ static int build_dyn_power_table(struct cpufreq_cooling_device *cpufreq_device, 
		power_table[i].power = power;

	}



	if (i == 0) {

		ret = PTR_ERR(opp);

		goto unlock;

	}

	rcu_read_unlock();



	if (i != num_opps)

		return PTR_ERR(opp);



	cpufreq_device->cpu_dev = dev;

	cpufreq_device->dyn_power_table = power_table;

	cpufreq_device->dyn_power_table_entries = i;



unlock:

	rcu_read_unlock();

	return ret;

	return 0;

}



static u32 cpu_freq_to_power(struct cpufreq_cooling_device *cpufreq_device,