Re: [OSADL QA 3.18.9-rt5 #1]

[Carsten Emde <C.Emde@osadl.org>]

Hi Sebastian,

>>> an Intel Bay Trail board (Intel(R) Celeron(R) CPU  J1900  @ 1.99GHz) at
>>> the OSADL QA Farm rack #b/slot #6 (https://www.osadl.org/?id=1894) stops
>>> working every 12 to 36 hours. The only way to get the board back to work
>> [..]
> Could you try this:
> --
> Subject: [PATCH] kernel/irq_work: fix no_hz deadlock
>
> Invoking NO_HZ's irq_work callback from timer irq is not working very
> well if the callback decides to invoke hrtimer_cancel():
>
> |hrtimer_try_to_cancel+0x55/0x5f
> |hrtimer_cancel+0x16/0x28
> |tick_nohz_restart+0x17/0x72
> |__tick_nohz_full_check+0x8e/0x93
> |nohz_full_kick_work_func+0xe/0x10
> |irq_work_run_list+0x39/0x57
> |irq_work_tick+0x60/0x67
> |update_process_times+0x57/0x67
> |tick_sched_handle+0x4a/0x59
> |tick_sched_timer+0x3b/0x64
> |__run_hrtimer+0x7a/0x149
> |hrtimer_interrupt+0x1cc/0x2c5
>
> and here we deadlock while waiting for the lock which we are holding.
> To fix this I'm doing the same thing that upstream is doing: is the
> irq_work dedicated IRQ and use it only for what is marked as "hirq"
> which should only be the FULL_NO_HZ related work.
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> [..]
Thanks a lot! Applied the patch and restarted the box. Given the fact 
that it took up to 36 hours until the board stopped, we unfortunately 
need to see at least one week of crash-free operation, before we may 
consider the bug as fixed.

	-Carsten.