netdev - Re: Soft-Lockup/Race in networking in 2.6.31-rc1+195 ( possibly?caused by netem)

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Date:	Wed, 8 Jul 2009 23:27:30 +0100
From:	Joao Correia <joaomiguelcorreia@...il.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Andres Freund <andres@...razel.de>,
	Arun R Bharadwaj <arun@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Stephen Hemminger <shemminger@...tta.com>,
	netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: Soft-Lockup/Race in networking in 2.6.31-rc1+195 ( 
	possibly?caused by netem)

On Wed, Jul 8, 2009 at 11:07 PM, Jarek Poplawski<jarkao2@...il.com> wrote:
> On Wed, Jul 08, 2009 at 10:44:47PM +0100, Joao Correia wrote:
>> Hello again
> Hello!
>
> ...
>> So again, the only thing that stops that freeze is  `echo 0 >>
>> /proc/sys/kernel/timer_migration`. Apologies for pointing you in the
>> wrong direction.
>
> No problem: the direction is almost right, we only need one U-turn ;-)
> In case you're not bored or too bored, one little patch to check the
> other side (after reverting the previous patch).
>
> Thanks,
> Jarek P.
> ---
>
>  kernel/hrtimer.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
> index 9002958..23387e4 100644
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -203,7 +203,7 @@ switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base,
>        int cpu, preferred_cpu = -1;
>
>        cpu = smp_processor_id();
> -#if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
> +#if 0
>        if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu)) {
>                preferred_cpu = get_nohz_load_balancer();
>                if (preferred_cpu >= 0)
>

(this time i triple-checked :-) )

So, with only this last patch applied, no freeze. No need to disable
anything through /proc.

Where should i put the BUG_ON?

Joao Correia
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