On 07/31/2014 06:13 PM, Saravana Kannan wrote:
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:
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
the governor? scaling_governor doesn't cut it since that file is not
policy exit event to governor. If it's ondemand, try reading/write it's
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
I'll put something like
echo ondemand > /sys/devices/system/cpu/cpu1/cpufreq/scaling_governor
echo 20000 > /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
The actual race can only happen with 2 threads. I'm just trying to trigger a
lockdep warning here.
I ran the above in two separate terminals with cpuset -c 0 and cpuset -c 1 to
multi-thread it all. No deadlock or LOCKDEP trace after about 1/2 hour, so I
think we're in the clear on that concern.