On 08/01/2014 12:54 PM, Stephen Boyd wrote:

On 08/01/14 12:43, Prarit Bhargava wrote:

quoted

On 08/01/2014 03:36 PM, Stephen Boyd wrote:

quoted

On 08/01/14 12:15, Prarit Bhargava wrote:

quoted

On 08/01/2014 01:18 PM, Stephen Boyd wrote:

quoted

On 08/01/14 03:27, Prarit Bhargava wrote:

quoted

Can you send me the test and the trace of the deadlock?  I'm not creating it with:

This was with conservative as the default, and switching to ondemand

# cd /sys/devices/system/cpu/cpu2/cpufreq
# ls
affected_cpus                  scaling_available_governors
conservative                   scaling_cur_freq
cpuinfo_cur_freq               scaling_driver
cpuinfo_max_freq               scaling_governor
cpuinfo_min_freq               scaling_max_freq
cpuinfo_transition_latency     scaling_min_freq
related_cpus                   scaling_setspeed
scaling_available_frequencies  stats
# cat conservative/down_threshold
20
# echo ondemand > scaling_governor

Thanks Stephen,

There's obviously a difference in our .configs.  I have a global conservative
directory, ie) /sys/devices/system/cpu/cpufreq/conservative instead of a per-cpu
governor file.

ie) what are your .config options for CPUFREQ?

Mine are:

#
# CPU Frequency scaling
#
CONFIG_CPU_FREQ=y
CONFIG_CPU_FREQ_GOV_COMMON=y
CONFIG_CPU_FREQ_STAT=m
CONFIG_CPU_FREQ_STAT_DETAILS=y
# CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_USERSPACE is not set
# CONFIG_CPU_FREQ_DEFAULT_GOV_ONDEMAND is not set
CONFIG_CPU_FREQ_DEFAULT_GOV_CONSERVATIVE=y
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=y
CONFIG_CPU_FREQ_GOV_USERSPACE=y
CONFIG_CPU_FREQ_GOV_ONDEMAND=y
CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y

Is there some other config option I have to set?

I have the same options. The difference is that my driver has a governor
per policy. That's set with the CPUFREQ_HAVE_GOVERNOR_PER_POLICY flag.
If I remove that flag I can't trigger the lockdep splat anymore with
this sequence and your patch.

I see -- so you're seeing this on arm then?  If so, let me know so I can reserve
one to work on :)

I only have ARM to test on. You can set this flag in your cpufreq driver
if you have independently scaling CPU frequencies, so it isn't
necessarily an ARM thing.

Sorry, forgot to mention this in the earlier email. But yeah, this is a 
totally SW feature. You should be able to enable this flag in your driver.

-Saravana

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