Re: [PATCH] hwmon: (coretemp) Handle frozen hotplug state correctly

[Tommi Rantala]

2017-05-10 23:09 GMT+03:00 Guenter Roeck <linux@xxxxxxxxxxxx>:
> On Wed, May 10, 2017 at 10:16:33PM +0300, Tommi Rantala wrote:
>> 2017-05-10 17:30 GMT+03:00 Thomas Gleixner <tglx@xxxxxxxxxxxxx>:
>> > The recent conversion to the hotplug state machine missed that the original
>> > hotplug notifiers did not execute in the frozen state, which is used on
>> > suspend on resume.
>> >
>> > This does not matter on single socket machines, but on multi socket systems
>> > this breaks when the device for a non-boot socket is removed when the last
>> > CPU of that socket is brought offline. The device removal locks up the
>> > machine hard w/o any debug output.
>> >
>> > Prevent executing the hotplug callbacks when cpuhp_tasks_frozen is true.
>> >
>> > Thanks to Tommi for providing debug information patiently while I failed to
>> > spot the obvious.
>> >
>> > Fixes: e00ca5df37ad ("hwmon: (coretemp) Convert to hotplug state machine")
>> > Reported-by: Tommi Rantala <tt.rantala@xxxxxxxxx>
>> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
>>
>> Many thanks, I can confirm that it works well!
>>
> Ok if I add your Tested-by: ?

Sure!

Tested-by: Tommi Rantala <tt.rantala@xxxxxxxxx>

> Thanks,
> Guenter
>
>> -Tommi
>>
>> > ---
>> >  drivers/hwmon/coretemp.c |   14 ++++++++++++++
>> >  1 file changed, 14 insertions(+)
>> >
>> > --- a/drivers/hwmon/coretemp.c
>> > +++ b/drivers/hwmon/coretemp.c
>> > @@ -605,6 +605,13 @@ static int coretemp_cpu_online(unsigned
>> >         struct platform_data *pdata;
>> >
>> >         /*
>> > +        * Don't execute this on resume as the offline callback did
>> > +        * not get executed on suspend.
>> > +        */
>> > +       if (cpuhp_tasks_frozen)
>> > +               return 0;
>> > +
>> > +       /*
>> >          * CPUID.06H.EAX[0] indicates whether the CPU has thermal
>> >          * sensors. We check this bit only, all the early CPUs
>> >          * without thermal sensors will be filtered out.
>> > @@ -654,6 +661,13 @@ static int coretemp_cpu_offline(unsigned
>> >         struct temp_data *tdata;
>> >         int indx, target;
>> >
>> > +       /*
>> > +        * Don't execute this on suspend as the device remove locks
>> > +        * up the machine.
>> > +        */
>> > +       if (cpuhp_tasks_frozen)
>> > +               return 0;
>> > +
>> >         /* If the physical CPU device does not exist, just return */
>> >         if (!pdev)
>> >                 return 0;