Messages in this thread | | | Date | Mon, 11 Aug 2008 14:23:59 -0700 (PDT) | Subject | Re: [PATCH] BUG: using smp_processor_id() in preemptible [00000000] code: caller is __qdisc_run | From | David Miller <> |
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From: Peter Zijlstra <a.p.zijlstra@chello.nl> 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@gmail.com> > > 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.
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