On 8 February 2013 04:37, Rafael J. Wysocki rjw@sisk.pl 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@linaro.org 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@linaro.org --- 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);