From 540a375822a40675868c5f62ae57b608a579e56a Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Tue, 26 Mar 2019 12:16:58 +0100 Subject: cpufreq: Add cpufreq_cpu_acquire() and cpufreq_cpu_release() It sometimes is necessary to find a cpufreq policy for a given CPU and acquire its rwsem (for writing) immediately after that, so introduce cpufreq_cpu_acquire() as a helper for that and the complementary cpufreq_cpu_release(). Make cpufreq_update_policy() use the new functions. Signed-off-by: Rafael J. Wysocki Acked-by: Viresh Kumar --- drivers/cpufreq/cpufreq.c | 56 +++++++++++++++++++++++++++++++++++++++-------- 1 file changed, 47 insertions(+), 9 deletions(-) (limited to 'drivers/cpufreq') diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index bb63347f6af1..d8fc395af773 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -250,6 +250,51 @@ void cpufreq_cpu_put(struct cpufreq_policy *policy) } EXPORT_SYMBOL_GPL(cpufreq_cpu_put); +/** + * cpufreq_cpu_release - Unlock a policy and decrement its usage counter. + * @policy: cpufreq policy returned by cpufreq_cpu_acquire(). + */ +static void cpufreq_cpu_release(struct cpufreq_policy *policy) +{ + if (WARN_ON(!policy)) + return; + + lockdep_assert_held(&policy->rwsem); + + up_write(&policy->rwsem); + + cpufreq_cpu_put(policy); +} + +/** + * cpufreq_cpu_acquire - Find policy for a CPU, mark it as busy and lock it. + * @cpu: CPU to find the policy for. + * + * Call cpufreq_cpu_get() to get a reference on the cpufreq policy for @cpu and + * if the policy returned by it is not NULL, acquire its rwsem for writing. + * Return the policy if it is active or release it and return NULL otherwise. + * + * The policy returned by this function has to be released with the help of + * cpufreq_cpu_release() in order to release its rwsem and balance its usage + * counter properly. + */ +static struct cpufreq_policy *cpufreq_cpu_acquire(unsigned int cpu) +{ + struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); + + if (!policy) + return NULL; + + down_write(&policy->rwsem); + + if (policy_is_inactive(policy)) { + cpufreq_cpu_release(policy); + return NULL; + } + + return policy; +} + /********************************************************************* * EXTERNALLY AFFECTING FREQUENCY CHANGES * *********************************************************************/ @@ -2337,17 +2382,12 @@ static int cpufreq_set_policy(struct cpufreq_policy *policy, */ void cpufreq_update_policy(unsigned int cpu) { - struct cpufreq_policy *policy = cpufreq_cpu_get(cpu); + struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpu); struct cpufreq_policy new_policy; if (!policy) return; - down_write(&policy->rwsem); - - if (policy_is_inactive(policy)) - goto unlock; - /* * BIOS might change freq behind our back * -> ask driver for current freq and notify governors about a change @@ -2364,9 +2404,7 @@ void cpufreq_update_policy(unsigned int cpu) cpufreq_set_policy(policy, &new_policy); unlock: - up_write(&policy->rwsem); - - cpufreq_cpu_put(policy); + cpufreq_cpu_release(policy); } EXPORT_SYMBOL(cpufreq_update_policy); -- cgit v1.2.3