linux-kernel - Re: NOHZ: local_softirq

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Message-ID: <20120625123809.GA12623@sig21.net>
Date:	Mon, 25 Jun 2012 14:38:09 +0200
From:	Johannes Stezenbach <js@...21.net>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Dave Jones <davej@...hat.com>,
	Marc Dionne <marc.c.dionne@...il.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: NOHZ: local_softirq_pending 08

Hi,

On Fri, Jun 08, 2012 at 11:53:28PM +0200, Francois Romieu wrote:
> Thomas Gleixner <tglx@...utronix.de> :
> [...]
> > Though the problem is, that it is neither called in interrupt context
> > nor with bh disabled, so nothing invokes the softirq before it reaches
> > idle.
> > 
> > In hard interrupt context the pending flag is evaluated in irq_exit()
> > and the softirqs are invoked from there. If you call that from thread
> > context, then a bh_disable/enable pair will make sure that the pending
> > softirq is invoked. Did I miss some more ___underscore magic which
> > does that ?
> 
> No. You _are_ right.
> 
> That's why 98ddf986fca17840e46e070354b7e2cd2169da15 triggered the
> message: it removed the last bh lock in the r8169 slow work context.
> 
> /me slaps head...
> 
> The whole thing is probably moot. Dave, can you apply the patch
> below on top of a fresh kernel tree ?
> 
> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
> index 4a05b68..d452441 100644
> --- a/drivers/net/ethernet/realtek/r8169.c
> +++ b/drivers/net/ethernet/realtek/r8169.c
> @@ -5934,11 +5934,7 @@ static void rtl_slow_event_work(struct rtl8169_private *tp)
>  	if (status & LinkChg)
>  		__rtl8169_check_link_status(dev, tp, tp->mmio_addr, true);
>  
> -	napi_disable(&tp->napi);
> -	rtl_irq_disable(tp);
> -
> -	napi_enable(&tp->napi);
> -	napi_schedule(&tp->napi);
> +	rtl_irq_enable_all(tp);
>  }
>  
>  static void rtl_task(struct work_struct *work)

I just upgraded my rarely-used Atom based netbook from 3.3.5 to 3.4.4
and got the "NOHZ: local_softirq_pending 08" message.
Should this patch go into stable?

Johannes
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