Hi Nathan,
Sorry for pointing out this so late but i still feel we are missing something
really important.
On 22 February 2013 21:54, Nathan Zimmer <nzimmer@xxxxxxx> wrote:
> - read_lock_irqsave(&cpufreq_driver_lock, flags);
> + rcu_read_lock();
> + freqs->flags = rcu_dereference(cpufreq_driver)->flags;
> policy = per_cpu(cpufreq_cpu_data, freqs->cpu);
> - read_unlock_irqrestore(&cpufreq_driver_lock, flags);
> + rcu_read_unlock();
> - write_lock_irqsave(&cpufreq_driver_lock, flags);
> + spin_lock_irqsave(&cpufreq_driver_lock, flags);
> for_each_cpu(j, policy->cpus) {
> per_cpu(cpufreq_cpu_data, j) = policy;
> per_cpu(cpufreq_policy_cpu, j) = policy->cpu;
> }
> - write_unlock_irqrestore(&cpufreq_driver_lock, flags);
> + spin_unlock_irqrestore(&cpufreq_driver_lock, flags);
Look at how we are protecting cpufreq_cpu_data here. rcu_read_[un]lock()
only marks the start/end of critical section. How are we sure here that
cpufreq_cpu_data is not read simultaneously when we are updating it?
rcu lock/unlock only works for cpufreq_driver pointer only and not for
this data. We still need the same locking for for cpufreq_cpu_data.
What do you say?
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