On 8 February 2013 04:37, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> BTW, there still are locking problems in linux-next. Why do we need
> to take cpufreq_driver_lock() around driver->init() in cpufreq_add_dev(),
> in particular?
I thought a bit more and realized there is no such limitation on
cpufreq_driver->ops about calling routines which can sleep. And thus
we shoudln't
have locks around any of these. I have got a patch for it, that i
would fold-back into
the original patch that introduced locking fixes (attached too for testing):
From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Date: Fri, 8 Feb 2013 10:35:31 +0530
Subject: [PATCH] cpufreq: Remove unnecessary locking
I have placed some locks intentionally around calls to driver->ops (init/exit),
which look to be wrong as these calls can call routines that potentially sleep.
Lets remove these locks.
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
---
drivers/cpufreq/cpufreq.c | 7 -------
1 file changed, 7 deletions(-)
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
index 5d8a422..04aab05 100644
--- a/drivers/cpufreq/cpufreq.c
+++ b/drivers/cpufreq/cpufreq.c
@@ -795,10 +795,8 @@ static int cpufreq_add_dev_interface(unsigned int cpu,
if (ret) {
pr_debug("setting policy failed\n");
- spin_lock_irqsave(&cpufreq_driver_lock, flags);
if (driver->exit)
driver->exit(policy);
- spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
}
return ret;
@@ -920,17 +918,14 @@ static int cpufreq_add_dev(struct device *dev,
struct subsys_interface *sif)
init_completion(&policy->kobj_unregister);
INIT_WORK(&policy->update, handle_update);
- spin_lock_irqsave(&cpufreq_driver_lock, flags);
/* call driver. From then on the cpufreq must be able
* to accept all calls to ->verify and ->setpolicy for this CPU
*/
ret = driver->init(policy);
if (ret) {
pr_debug("initialization failed\n");
- spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
goto err_set_policy_cpu;
}
- spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
/* related cpus should atleast have policy->cpus */
cpumask_or(policy->related_cpus, policy->related_cpus, policy->cpus);
@@ -1100,10 +1095,8 @@ static int __cpufreq_remove_dev(struct device
*dev, struct subsys_interface *sif
wait_for_completion(cmp);
pr_debug("wait complete\n");
- spin_lock_irqsave(&cpufreq_driver_lock, flags);
if (driver->exit)
driver->exit(data);
- spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
free_cpumask_var(data->related_cpus);
free_cpumask_var(data->cpus);
Attachment:
0001-cpufreq-Remove-unnecessary-locking.patch
Description: Binary data
