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

Rafael J. Wysocki
2009-11-09T15:46:16Z

On Monday 09 November 2009, Mike Galbraith wrote:
> On Mon, 2009-11-09 at 15:27 +0100, Rafael J. Wysocki wrote:
> > On Monday 09 November 2009, Mike Galbraith wrote:
> > > On Mon, 2009-11-09 at 15:02 +0100, Thomas Gleixner wrote:
> > > > On Mon, 9 Nov 2009, Ingo Molnar wrote:
> > > > >
> > >
> > > > > 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.
> > >
> > > I wonder if that's not intimately related to the problem I had, namely
> > > newidle balancing offline CPUs as they're coming up, making a mess of
> > > cpu enumeration.
> >
> > Very likely. What did you do to fix it?
>
> You don't really wanna know. In 31 with newidle enabled, the below
> fixed it. It won't fix 32, though it might cure the resume problem.

OK, I'll give it a try.

> diff --git a/kernel/sched.c b/kernel/sched.c
> index 1b59e26..6e71932 100644
> --- a/kernel/sched.c
> +++ b/kernel/sched.c
> @@ -4032,7 +4049,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
> unsigned long flags;
> struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
>
> - cpumask_setall(cpus);
> + cpumask_copy(cpus, cpu_online_mask);
>
> /*
> * When power savings policy is enabled for the parent domain, idle
> @@ -4195,7 +4212,7 @@ load_balance_newidle(int this_cpu, struct rq *this_rq, struct sched_domain *sd)
> int all_pinned = 0;
> struct cpumask *cpus = __get_cpu_var(load_balance_tmpmask);
>
> - cpumask_setall(cpus);
> + cpumask_copy(cpus, cpu_online_mask);
>
> /*
> * When power savings policy is enabled for the parent domain, idle

Thanks,
Rafael