On 2015/2/2 11:24, Viresh Kumar wrote:
On 2 February 2015 at 08:50, ethan zhao <ethan.z...@oracle.com> wrote:
This seems couldn't prevent all the 'bad thing' from happening, E.G.
Thread A: Workqueue: kacpi_notify
acpi_processor_notify()
acpi_processor_ppc_has_changed()
cpufreq_update_policy()
cpufreq_cpu_get()
We take cpufreq_driver_lock() here, and so this will
block thread B.
No, there is no cpufreq_driver_lock acquired between
cpufreq_cpu_get() and cpufreq_cpu_put()
beginning the deference of policy Thread B:
... ... __cpufreq_remove_dev_finish()
cpufreq_policy_free(policy);
Perhaps move policy->rwsem out side the policy structure is a way to avoid
it completely.
and you could stopping the PPC thread stepping forward as my patch as
temporary workaround.
I couldn't understand your problem completely. Apart from giving a detailed
look of what's going on both threads, always specify where the BUG actually
is..
The problem is you are using a rwsem inside policy structure to protect its
assessment, that is bad design.
Thanks,
Ethan
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