linux-kernel - Re: NOHZ: local_softirq

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Message-ID: <20120608215328.GB26175@electric-eye.fr.zoreil.com>
Date:	Fri, 8 Jun 2012 23:53:28 +0200
From:	Francois Romieu <romieu@...zoreil.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	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

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)
--
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