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Date: Mon, 01 Apr 2013 22:41:27 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Nathan Zimmer <nzimmer@....com>
Cc: viresh.kumar@...aro.org, cpufreq@...r.kernel.org,
linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 2/2] cpufreq: covert the cpufreq_data_lock to a spinlock
On Monday, April 01, 2013 03:11:09 PM Nathan Zimmer wrote:
> This eliminates the rest of the contention found in __cpufreq_cpu_get.
> I am not seeing a way to use the rcu so we will have to make due with a
> rwlock for now.
>
> Cc: Viresh Kumar <viresh.kumar@...aro.org>
> Cc: "Rafael J. Wysocki" <rjw@...k.pl>
> Signed-off-by: Nathan Zimmer <nzimmer@....com>
I've already applied this one.
Can you please check if the version in my tree is OK?
Rafael
> ---
> drivers/cpufreq/cpufreq.c | 38 +++++++++++++++++++-------------------
> 1 file changed, 19 insertions(+), 19 deletions(-)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 5139eab..7438c34 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -42,7 +42,7 @@
> static struct cpufreq_driver __rcu *cpufreq_driver;
> static DEFINE_SPINLOCK(cpufreq_driver_lock);
>
> -static DEFINE_SPINLOCK(cpufreq_data_lock);
> +static DEFINE_RWLOCK(cpufreq_data_lock);
> static DEFINE_PER_CPU(struct cpufreq_policy *, cpufreq_cpu_data);
> #ifdef CONFIG_HOTPLUG_CPU
> /* This one keeps track of the previously set governor of a removed CPU */
> @@ -150,7 +150,7 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
> goto err_out_unlock;
>
> /* get the CPU */
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + read_lock_irqsave(&cpufreq_data_lock, flags);
> data = per_cpu(cpufreq_cpu_data, cpu);
>
> if (!data)
> @@ -159,13 +159,13 @@ static struct cpufreq_policy *__cpufreq_cpu_get(unsigned int cpu, bool sysfs)
> if (!sysfs && !kobject_get(&data->kobj))
> goto err_out_put_module;
>
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + read_unlock_irqrestore(&cpufreq_data_lock, flags);
> rcu_read_unlock();
> return data;
>
> err_out_put_module:
> module_put(driver->owner);
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + read_unlock_irqrestore(&cpufreq_data_lock, flags);
> err_out_unlock:
> rcu_read_unlock();
> err_out:
> @@ -276,9 +276,9 @@ void cpufreq_notify_transition(struct cpufreq_freqs *freqs, unsigned int state)
> pr_debug("notification %u of frequency transition to %u kHz\n",
> state, freqs->new);
>
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + read_lock_irqsave(&cpufreq_data_lock, flags);
> policy = per_cpu(cpufreq_cpu_data, freqs->cpu);
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + read_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> switch (state) {
>
> @@ -802,12 +802,12 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
> }
> rcu_read_unlock();
>
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + write_lock_irqsave(&cpufreq_data_lock, flags);
> for_each_cpu(j, policy->cpus) {
> per_cpu(cpufreq_cpu_data, j) = policy;
> per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
> }
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + write_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> ret = cpufreq_add_dev_symlink(cpu, policy);
> if (ret)
> @@ -858,12 +858,12 @@ static int cpufreq_add_policy_cpu(unsigned int cpu, unsigned int sibling,
>
> lock_policy_rwsem_write(sibling);
>
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + write_lock_irqsave(&cpufreq_data_lock, flags);
>
> cpumask_set_cpu(cpu, policy->cpus);
> per_cpu(cpufreq_policy_cpu, cpu) = policy->cpu;
> per_cpu(cpufreq_cpu_data, cpu) = policy;
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + write_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> unlock_policy_rwsem_write(sibling);
>
> @@ -918,15 +918,15 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
>
> #ifdef CONFIG_HOTPLUG_CPU
> /* Check if this cpu was hot-unplugged earlier and has siblings */
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + read_lock_irqsave(&cpufreq_data_lock, flags);
> for_each_online_cpu(sibling) {
> struct cpufreq_policy *cp = per_cpu(cpufreq_cpu_data, sibling);
> if (cp && cpumask_test_cpu(cpu, cp->related_cpus)) {
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + read_unlock_irqrestore(&cpufreq_data_lock, flags);
> return cpufreq_add_policy_cpu(cpu, sibling, dev);
> }
> }
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + read_unlock_irqrestore(&cpufreq_data_lock, flags);
> #endif
> #endif
>
> @@ -1006,10 +1006,10 @@ static int cpufreq_add_dev(struct device *dev, struct subsys_interface *sif)
> return 0;
>
> err_out_unregister:
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + write_lock_irqsave(&cpufreq_data_lock, flags);
> for_each_cpu(j, policy->cpus)
> per_cpu(cpufreq_cpu_data, j) = NULL;
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + write_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> kobject_put(&policy->kobj);
> wait_for_completion(&policy->kobj_unregister);
> @@ -1067,12 +1067,12 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
>
> pr_debug("%s: unregistering CPU %u\n", __func__, cpu);
>
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + write_lock_irqsave(&cpufreq_data_lock, flags);
>
> data = per_cpu(cpufreq_cpu_data, cpu);
> per_cpu(cpufreq_cpu_data, cpu) = NULL;
>
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + write_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> if (!data) {
> pr_debug("%s: No cpu_data found\n", __func__);
> @@ -1111,9 +1111,9 @@ static int __cpufreq_remove_dev(struct device *dev, struct subsys_interface *sif
> WARN_ON(lock_policy_rwsem_write(cpu));
> cpumask_set_cpu(cpu, data->cpus);
>
> - spin_lock_irqsave(&cpufreq_data_lock, flags);
> + write_lock_irqsave(&cpufreq_data_lock, flags);
> per_cpu(cpufreq_cpu_data, cpu) = data;
> - spin_unlock_irqrestore(&cpufreq_data_lock, flags);
> + write_unlock_irqrestore(&cpufreq_data_lock, flags);
>
> unlock_policy_rwsem_write(cpu);
>
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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