Re: [PATCH] NOHZ: local_softirq_pending with tickless plip

[David Miller <davem@davemloft.net>]

From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 17 May 2007 12:52:11 +0200

> On Wed, 2007-05-16 at 15:00 +0200, Mikulas Patocka wrote:
> > Hi
> > 
> > On one of my machines with tickless kernel and plip I get messages :
> 
> I bet this is a machine a P4 with Hyperthreading enabled ?
> 
> > NOHZ: local_softirq_pending 08
> > 
> > always when using plip (on other machine with tickless kernel and plip I 
> > get no errors). Thebug happens both on 2.6.21 and 2.6.22-rc1
> > 
> > This patch fixes that. Note that plip calls netif_rx neither from hardware 
> > interrupt nor from ksoftirqd, so there is no one who would wake 
> > ksoftirqd then. netif_tx calls only 
> > __raise_softirq_irqoff(NET_RX_SOFTIRQ), which sets softirq bit, but 
> > doesn't wake ksoftirqd.
> 
> Dave, 
> 
> can we please get rid of __raise_softirq_irqoff() at all ? These micro
> optimizations are causing more trouble than they are worth.

Actually I think this is pointing out a bug, in that plip is not
invoking things in the proper context, which will likely cause
other problems :-)

I'll put this on my TODO list and look into this.