On Mon, 11 Aug 2008, David Miller wrote: > From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Date: Mon, 11 Aug 2008 23:09:38 +0200 > > > On Mon, 2008-08-11 at 14:00 -0700, David Miller wrote: > > > From: "John Kacur" <jkacur@xxxxxxxxx> > > > Date: Mon, 11 Aug 2008 15:11:46 +0200 > > > > > > > __qdisc_run() calls qdisc_restart() which calls > > > > handle_dev_cpu_collision(skb, dev, q); and then the problem shows up > > > > here: > > > > __get_cpu_var(netdev_rx_stat).cpu_collision++; > > > > > > > > The solution is to disable interrupts around the above increment. Here > > > > is an attached patch to do so. (Thank's to Peter Zijlstra for help in > > > > the analysis and dropping the answer in my lap, so if I got it right > > > > it is due to his help, but if I messed it up, then I did that part all > > > > by myself.) > > > > > > __qdisc_run() always runs in software interrupt context, > > > so I guess this is some problem with the -rt stuff running > > > software interrupts in threads? > > > > Hmm, good point - and those threads should be cpu affine on -rt if I'm > > not mistaken. Steven, do you happen to remember details? > > The key issue is whether those threads run software interrupts > in a compatible environment. And such a proper environment allows > plain smp_processor_id() without any special preparations. > Yes, we have a softirq thread per CPU. We should have a test in the smp_processor_id for rt to not bug if it is called by known "per_cpu" threads. -- Steve -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
