Re: [Xen-devel] [PATCH v3 07/11] x86/intel_pstate: changes in cpufreq_del_cpu for CPU offline

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 23.06.15 at 08:16, <wei.w.wang@xxxxxxxxx> wrote:
> On 19/06/2015 17:44, Jan Beulich wrote:
>> >>> On 11.06.15 at 10:28, <wei.w.wang@xxxxxxxxx> wrote:
>> > cpufreq_cpu_policy is used in intel_pstate_set_pstate(), so we change
>> > to NULL it after the call of cpufreq_driver->exit. Otherwise, a
>> > calltrace will show up on your screen due to the reference of a NULL
>> > pointer when you power down the system.
>> 
>> Apart from what was already said on this patch, I think it is placed too 
>> late in
>> this series (should precede patch 6) or, even better, not needed at all: 
>> ->exit()
>> gets passed the policy being cleaned up, so I don't follow why the driver
>> needs to consult the per-CPU field to obtain it.
> 
>> Plus, if the patch is to be kept, the description suggesting this to be a
>> problem at system shutdown only is wrong - it can equally well happen while
>> offlining a CPU. Just saying that the pointer is still needed would be 
>> sufficient.
> 
> It's needed. When unplugging a CPU, the intel_pstate driver sets it to run 
> with the lowest P-state.

I understand the latter, but this doesn't explain why you can't do
what I suggested above.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel