On Sat, 6 Apr 2013, Srivatsa S. Bhat wrote: > Hi Dave, > > On 04/06/2013 03:13 AM, Dave Hansen wrote: > > Hey Thomas, > > > > I seem to be running in to smpboot_thread_fn()'s > > > > BUG_ON(td->cpu != smp_processor_id());
That should be WARN_ON of course. Stupid me. > > pretty regularly, both at boot and if I boot with maxcpus=x and then > > online the CPUs from sysfs after boot. It's a 160-logical-cpu system, > > so it's quite a beast. I _seem_ to be hitting it more often at higher > > cpu counts, but it doesn't trigger on bringing up a particular CPU as > > far as I can tell. > > > > This is on a pull of mainline from today, e0a77f263. Any ideas? > > > > Dave Jones had reported a similar problem some time back and Hillf had > proposed a fix. I guess it slipped through the cracks and never went > upstream. > > Here is the link: https://lkml.org/lkml/2013/1/19/1 This is Hillfs proposed patch: > --- a/kernel/kthread.c Sat Jan 19 13:03:52 2013 > +++ b/kernel/kthread.c Sat Jan 19 13:17:54 2013 > @@ -306,6 +306,7 @@ struct task_struct *kthread_create_on_cp > return p; > set_bit(KTHREAD_IS_PER_CPU, &to_kthread(p)->flags); > to_kthread(p)->cpu = cpu; > + __kthread_bind(p, cpu); > /* Park the thread to get it out of TASK_UNINTERRUPTIBLE state */ > kthread_park(p); > return p; That's bogus. Simply because when we create the thread then the thread status is HP_THREAD_NONE and the path with the BUG_ON is only entered with status == HP_THREAD_ACTIVE: if (ht->park && td->status == HP_THREAD_ACTIVE) { So in Dave's case the thread was already created and has entered active state. > >> [ 790.226909] Pid: 3909, comm: migration/135 Tainted: G W > >> 3.9.0-rc5-00184-gb6a9b7f-dirty #118 FUJITSU-SV PRIMEQUEST 1800E2/SB Hmm, it's the migration thread which trips over this. Oh joy! Dave, does the issue reproduce with function tracing enabled? For a first shot it's probably enough to filter on smpboot_* functions plus sched_switch and sched_wakeup events. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
