linux-kernel - Re: NOHZ: local_softirq

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Message-ID: <CAB9dFdvXz85hc0p_Yanir4N6jJf9Q26crgU6a1r8VjWh8LXeHg@mail.gmail.com>
Date:	Fri, 8 Jun 2012 18:33:09 -0400
From:	Marc Dionne <marc.c.dionne@...il.com>
To:	Francois Romieu <romieu@...zoreil.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: NOHZ: local_softirq_pending 08

On Fri, Jun 8, 2012 at 5:53 PM, Francois Romieu <romieu@...zoreil.com> 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)

That works for me - no warnings after several reboots and bringing the
interface up/down many times.

Marc
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