Messages in this thread | | | Date | Thu, 31 Jul 2014 15:13:58 -0700 | From | Saravana Kannan <> | Subject | Re: [PATCH] cpufreq, store_scaling_governor requires policy->rwsem to be held for duration of changing governors [v2] |
| |
On 07/31/2014 02:08 PM, Prarit Bhargava wrote: > > > On 07/31/2014 04:38 PM, Saravana Kannan wrote: >> On 07/31/2014 01:30 PM, Prarit Bhargava wrote: >>> >>> >>> On 07/31/2014 04:24 PM, Saravana Kannan wrote: >>>> >>>> Prarit, >>>> >>>> I'm not an expert on sysfs locking, but I would think the specific sysfs lock >>>> would depend on the file/attribute group. So, can you please try to hotplug a >>>> core in/out (to trigger the POLICY_EXIT) and then read a sysfs file exported by >>>> the governor? scaling_governor doesn't cut it since that file is not removed on >>>> policy exit event to governor. If it's ondemand, try reading/write it's sampling >>>> rate file. >>> >>> Thanks Saravana -- will do. I will get back to you shortly on this. >>> >> >> Thanks. Btw, in case you weren't already aware of it. You'll have to hoplug out >> all the CPUs in a cluster to trigger a POLICY_EXIT for that cluster/policy. > > Yep -- the affected_cpus file should show all the cpus in the policy IIRC. One > of the systems I have has 1 cpu/policy and has 48 threads so the POLICY_EXIT is > called. > > I'll put something like > > while [1]; > do > echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor > cat /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate > echo 20000 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate > cat /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate > echo 0 > /sys/devices/system/cpu/cpu1/online > sleep 1 > echo 1 > /sys/devices/system/cpu/cpu1/online > sleep 1 > done >
The actual race can only happen with 2 threads. I'm just trying to trigger a lockdep warning here.
-Saravana
-- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, hosted by The Linux Foundation
| |