linux-kernel - Re: CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH] acpi : remove power from acpi_processor

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Date:	Thu, 6 Sep 2012 22:04:11 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>
Cc:	xen-devel@...ts.xensource.com, linaro-dev@...ts.linaro.org,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	linux-pm@...r.kernel.org, linux-acpi@...r.kernel.org,
	lenb@...nel.org, Frederic Weisbecker <fweisbec@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: CONFIG_NO_HZ + CONFIG_CPU_IDLE freeze the system (Was Re: [PATCH] acpi : remove power from acpi_processor_cx structure)

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@...aro.org>
> >>>>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.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@...hat.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@...emloft.net>
>     Signed-off-by: Cong Wang <amwang@...hat.com>
>     Signed-off-by: David S. Miller <davem@...emloft.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
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