Re: [patch 00/61] ANNOUNCE: lock validator -V1

[Arjan van de Ven]

> I'm feeling a bit overwhelmed by the voluminous output of this checker.
> Especially as (directly at least) cpufreq doesn't touch vma's, or mmap's.

the reporter doesn't have CONFIG_KALLSYMS_ALL enabled which gives
sometimes misleading backtraces (should lockdep just enable KALLSYMS_ALL
to get more useful bugreports?)

the problem is this, there are 2 scenarios in this bug:

One
---
store_scaling_governor takes policy->lock and then calls __cpufreq_set_policy
__cpufreq_set_policy calls __cpufreq_governor
__cpufreq_governor  calls __cpufreq_driver_target via cpufreq_governor_performance
__cpufreq_driver_target calls lock_cpu_hotplug() (which takes the hotplug lock)


Two
---
cpufreq_stats_init lock_cpu_hotplug() and then calls cpufreq_stat_cpu_callback
cpufreq_stat_cpu_callback calls cpufreq_update_policy
cpufreq_update_policy takes the policy->lock


so this looks like a real honest AB-BA deadlock to me...


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