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Subject[PATCH 6/6] cpufreq: Avoid calling cpufreq_verify_current_freq() from handle_update()
Date
On some occasions cpufreq_verify_current_freq() schedules a work whose
callback is handle_update(), which further calls cpufreq_update_policy()
which may end up calling cpufreq_verify_current_freq() again.

On the other hand, when cpufreq_update_policy() is called from
handle_update(), the pointer to the cpufreq policy is already available
but we still call cpufreq_cpu_acquire() to get it in
cpufreq_update_policy(), which should be avoided as well.

Fix both the issues by creating another helper
reeval_frequency_limits().

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
drivers/cpufreq/cpufreq.c | 26 ++++++++++++++++----------
1 file changed, 16 insertions(+), 10 deletions(-)

diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 4556a53fc764..0a73de7aae54 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -1115,13 +1115,25 @@ static int cpufreq_add_policy_cpu(struct cpufreq_policy *policy, unsigned int cp
return ret;
}

+static void reeval_frequency_limits(struct cpufreq_policy *policy)
+{
+ struct cpufreq_policy new_policy = *policy;
+
+ pr_debug("updating policy for CPU %u\n", policy->cpu);
+
+ new_policy.min = policy->user_policy.min;
+ new_policy.max = policy->user_policy.max;
+
+ cpufreq_set_policy(policy, &new_policy);
+}
+
static void handle_update(struct work_struct *work)
{
struct cpufreq_policy *policy =
container_of(work, struct cpufreq_policy, update);
- unsigned int cpu = policy->cpu;
- pr_debug("handle_update for cpu %u called\n", cpu);
- cpufreq_update_policy(cpu);
+
+ pr_debug("handle_update for cpu %u called\n", policy->cpu);
+ reeval_frequency_limits(policy);
}

static struct cpufreq_policy *cpufreq_policy_alloc(unsigned int cpu)
@@ -2378,7 +2390,6 @@ int cpufreq_set_policy(struct cpufreq_policy *policy,
void cpufreq_update_policy(unsigned int cpu)
{
struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu);
- struct cpufreq_policy new_policy;

if (!policy)
return;
@@ -2391,12 +2402,7 @@ void cpufreq_update_policy(unsigned int cpu)
(cpufreq_suspended || WARN_ON(!cpufreq_verify_current_freq(policy, false))))
goto unlock;

- pr_debug("updating policy for CPU %u\n", cpu);
- memcpy(&new_policy, policy, sizeof(*policy));
- new_policy.min = policy->user_policy.min;
- new_policy.max = policy->user_policy.max;
-
- cpufreq_set_policy(policy, &new_policy);
+ reeval_frequency_limits(policy);

unlock:
cpufreq_cpu_release(policy);
--
2.21.0.rc0.269.g1a574e7a288b
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