On Tue, Apr 11, 2017 at 05:49:53PM -0400, Steven Rostedt wrote:
> On Tue, 11 Apr 2017 14:44:43 -0700
> "Paul E. McKenney" <[email protected]> wrote:
>
>
> > Works for me!
> >
> > Hopefully it will also work for your computer. :-)
> >
> > And whew! Glad to see that the stall warnings worked!
>
> Ah! but I think I found a bug in synchronize_rcu_tasks()!
>
> Calling schedule isn't good enough. For rcu_tasks to continue, the task
> needs to schedule out. With my updated code, I just triggered:
>
> [ 196.276868] INFO: rcu_tasks detected stalls on tasks:
> [ 196.284294] ffff8800c26f8040: .. nvcsw: 2/2 holdout: 1 idle_cpu: -1/1
> [ 196.293175] event_benchmark R running task 30536 1127 2
> 0x10000000
> [ 196.302746] Call Trace:
> [ 196.307640] ? _raw_spin_unlock_irq+0x1f/0x50
> [ 196.314453] __schedule+0x222/0x1210
> [ 196.320476] ? pci_mmcfg_check_reserved+0xc0/0xc0
> [ 196.327616] ? preempt_count_add+0xb7/0xf0
> [ 196.334174] ? __asan_store8+0x15/0x70
> [ 196.340384] schedule+0x57/0xe0
> [ 196.345888] benchmark_event_kthread+0x2e/0x3c0
> [ 196.352823] kthread+0x178/0x1d0
> [ 196.358411] ? trace_benchmark_reg+0x80/0x80
> [ 196.365073] ? kthread_create_on_node+0xa0/0xa0
> [ 196.371999] ret_from_fork+0x2e/0x40
>
>
> And here my benchmark called schedule(), but nothing scheduled it out,
> and it still fails on rcu_tasks.
Good point!
Hmmmm... I cannot hook into rcu_note_context_switch() because that gets
called for preemption as well as for voluntary context switches.
How about cond_resched_rcu_qs()? Does that cover it?
Thanx, Paul
