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

[Dave Jones]

On Tue, May 30, 2006 at 07:45:47AM +0200, Arjan van de Ven wrote:

 > 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...

This looks a little clearer this morning.  I missed the fact that sys_init_module
isn't completely serialised, only the loading part. ->init routines can and will be
called in parallel.

I don't see where cpufreq_update_policy takes policy->lock though.
In my tree it just takes the per-cpu data->lock.

Time for more wake-up juice? or am I missing something obvious again?

		Dave

-- 
http://www.codemonkey.org.uk
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