netdev - Re: NMI lockup, 2.6.26 release

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Date:	Wed, 13 Aug 2008 10:28:11 +0300
From:	Denys Fedoryshchenko <denys@...p.net.lb>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: NMI lockup, 2.6.26 release

Just as proposal, maybe we can catch situation when "things going wrong" and 
panic? So we can forward some info to hrtimers guys?
If it is hrtimers bug...

On Tuesday 12 August 2008, Jarek Poplawski wrote:
> On Tue, Aug 12, 2008 at 02:31:40PM +0300, Denys Fedoryshchenko wrote:
> ...
>
> > With second patch it works fine, 9 days uptime now
>
> Great! I didn't expect it would be so easy with this strange problem.
> So, it looks like hrtimers could break probably after some
> overscheduling. The only problem with this is to find some reasonable
> limit which is both safe and doesn't harm resolution too much for
> others.
>
> IMHO this second patch with 1 jiffie watchdog resolution looks
> reasonable and should be acceptable, but it would be nice to check if
> we can go lower. Here is "the same" patch with only change in
> resolution (1/10 of jiffie). If there are any problems with testing
> this please let me know. (It should be applied after reverting
> patch #2.)
>
> Thanks,
> Jarek P.
>
> (testing patch #3)
> ---
>
>  net/sched/sch_htb.c |    8 +++++++-
>  1 files changed, 7 insertions(+), 1 deletions(-)
>
> diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
> index 30c999c..ff9e965 100644
> --- a/net/sched/sch_htb.c
> +++ b/net/sched/sch_htb.c
> @@ -162,6 +162,7 @@ struct htb_sched {
>
>  	int rate2quantum;	/* quant = rate / rate2quantum */
>  	psched_time_t now;	/* cached dequeue time */
> +	psched_time_t next_watchdog;
>  	struct qdisc_watchdog watchdog;
>
>  	/* non shaped skbs; let them go directly thru */
> @@ -920,7 +921,11 @@ static struct sk_buff *htb_dequeue(struct Qdisc *sch)
>  		}
>  	}
>  	sch->qstats.overlimits++;
> -	qdisc_watchdog_schedule(&q->watchdog, next_event);
> +	if (q->next_watchdog < q->now || next_event <=
> +	     q->next_watchdog - PSCHED_TICKS_PER_SEC / (10 * HZ)) {
> +		qdisc_watchdog_schedule(&q->watchdog, next_event);
> +		q->next_watchdog = next_event;
> +	}
>  fin:
>  	return skb;
>  }
> @@ -973,6 +978,7 @@ static void htb_reset(struct Qdisc *sch)
>  		}
>  	}
>  	qdisc_watchdog_cancel(&q->watchdog);
> +	q->next_watchdog = 0;
>  	__skb_queue_purge(&q->direct_queue);
>  	sch->q.qlen = 0;
>  	memset(q->row, 0, sizeof(q->row));
> --
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