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

Rafael J. Wysocki
Thu, 06 Sep 2012 20:04:11 -0000

On Thursday, September 06, 2012, Daniel Lezcano wrote:
> 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.

If it is present in the current Linus'' tree, you can just pull this one
and merge linux-pm-next into it.  It should merge without conflicts.

> 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 ?

Well, there are systems having problems with this configuration, but they
should be exceptional.  What system is that?

Rafael