CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH] acpi : remove power from acpi_processor_cx structure)

Daniel Lezcano
Thu, 06 Sep 2012 09:22:32 -0000

On 09/06/2012 09:54 AM, Daniel Lezcano wrote:
> On 09/05/2012 03:41 PM, Rafael J. Wysocki wrote:
>> On Saturday, September 01, 2012, Rafael J. Wysocki wrote:
>>> On Friday, August 31, 2012, Daniel Lezcano wrote:
>>>> On 07/24/2012 11:06 PM, Konrad Rzeszutek Wilk wrote:
>>>>> On Tue, Jul 24, 2012 at 11:12:29PM +0200, Daniel Lezcano
wrote:
>>>>>> Remove the power field as it is not used.
>>>>>>
>>>>>> Signed-off-by: Daniel Lezcano
<daniel.lezcano@linaro.org>
>>>>>> Cc: Konrad Rzeszutek Wilk
<konrad.wilk@oracle.com>
>>>>> Acked.
>>>> Hi Rafael,
>>>>
>>>> I did not see this patch going in. Is it possible to merge it ?
>>> I think so.  I''ll take care of it when I get back from
LinuxCon/Plumbers Conf.
>>> (early next week).
>> Applied to the linux-next branch of the linux-pm.git tree as v3.7
material.
> Thanks Rafael.
>
>> Are there any other patches you want me to consider for v3.7?
> Yes please, I have the per cpu latencies ready to be submitted but I
> want to do extra testing before. Unfortunately, the linux-pm-next hangs
> at boot time on my intel dual core (not related to the patchset).
>
> I am git bisecting right now.

I found the culprit. This is not related to the linux-pm tree but with
net-next.
The following patch introduced the issue.

commit 6bdb7fe31046ac50b47e83c35cd6c6b6160a475d
Author: Amerigo Wang <amwang@redhat.com>
Date:   Fri Aug 10 01:24:50 2012 +0000

    netpoll: re-enable irq in poll_napi()

    napi->poll() needs IRQ enabled, so we have to re-enable IRQ before
    calling it.

    Cc: David Miller <davem@davemloft.net>
    Signed-off-by: Cong Wang <amwang@redhat.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>

AFAICS, it has been fixed by commit
072a9c48600409d72aeb0d5b29fbb75861a06631 which is not yet in linux-pm-next.

I fall into this issue because NETCONSOLE is set, disabling it allowed
me to go further.

Unfortunately I am facing to some random freeze on the system which
seems to be related to CONFIG_NO_HZ=y and CONFIG_CPU_IDLE=y.

Disabling one of them, make the freezes to disappear.

Is it a known issue ?

Thanks in advance
  -- Daniel