Re: Help needed: Resume problems in 2.6.32-rc, perhaps related to preempt_count leakage in keventd

Thomas Gleixner
2009-11-09T14:04:09Z

On Mon, 9 Nov 2009, Ingo Molnar wrote:
>
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
>
> > On Monday 09 November 2009, Ingo Molnar wrote:
> > >
> > > * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > >
> > > > [ 2016.865041] BUG: using smp_processor_id() in preemptible [00000000] code: events/1/29920
> > > > [ 2016.865344] caller is vmstat_update+0x13/0x48
> > > > [ 2016.865522] Pid: 29920, comm: events/1 Not tainted 2.6.31-tst #158
> > > > [ 2016.865700] Call Trace:
> > > > [ 2016.865877] [<ffffffff811608e8>] debug_smp_processor_id+0xc4/0xd4
> > > > [ 2016.866052] [<ffffffff810a9ae1>] vmstat_update+0x13/0x48
> > > > [ 2016.866232] [<ffffffff81051ee6>] worker_thread+0x18b/0x22a
> > > > [ 2016.866409] [<ffffffff810a9ace>] ? vmstat_update+0x0/0x48
> > > > [ 2016.866578] [<ffffffff810556a5>] ? autoremove_wake_function+0x0/0x38
> > > > [ 2016.866749] [<ffffffff81288803>] ? _spin_unlock_irqrestore+0x35/0x37
> > > > [ 2016.866935] [<ffffffff81051d5b>] ? worker_thread+0x0/0x22a
> > > > [ 2016.867113] [<ffffffff8105547d>] kthread+0x69/0x71
> > > > [ 2016.867278] [<ffffffff8100c1aa>] child_rip+0xa/0x20
> > > > [ 2016.867450] [<ffffffff81055414>] ? kthread+0x0/0x71
> > > > [ 2016.867618] [<ffffffff8100c1a0>] ? child_rip+0x0/0x20
> > >
> > > a bug producing similar looking messages was fixed by:
> > >
> > > fd21073: sched: Fix affinity logic in select_task_rq_fair()
> > >
> > > but that bug was introduced by:
> > >
> > > a1f84a3: sched: Check for an idle shared cache in select_task_rq_fair()
> >
> > I guess these are tip commits?
>
> yep, tip:sched/core ones.
>
> > > Which is for v2.6.33, not v2.6.32.
> >
> > The one I saw was in the Linus' tree, quite obviously.
>
> ok, then my observation should not apply.

I think it _IS_ releated because the worker_thread is CPU affine and
the debug_smp_processor_id() check does:

if (cpumask_equal(&current->cpus_allowed, cpumask_of(this_cpu)))

which prevents that usage of smp_processor_id() in ksoftirqd and
keventd in preempt enabled regions is warned on.

We saw exaclty the same back trace with fd21073 (sched: Fix affinity
logic in select_task_rq_fair()).

Rafael, can you please add a printk to debug_smp_processor_id() so we
can see on which CPU we are running ? I suspect we are on the wrong
one.

Thanks,

tglx