On Mon, 09 Apr 2018 18:46:29 +1000 Benjamin Herrenschmidt <b...@kernel.crashing.org> wrote:
> On Fri, 2018-04-06 at 00:31 +1000, Nicholas Piggin wrote: > > irq_work_raise should not schedule the hardware decrementer interrupt > > unless it is called from NMI context. Doing so often just results in an > > immediate masked decrementer interrupt: > > > > <...>-550 90d... 4us : update_curr_rt <-dequeue_task_rt > > <...>-550 90d... 5us : dbs_update_util_handler <-update_curr_rt > > <...>-550 90d... 6us : arch_irq_work_raise <-irq_work_queue > > <...>-550 90d... 7us : soft_nmi_interrupt <-soft_nmi_common > > <...>-550 90d... 7us : printk_nmi_enter <-soft_nmi_interrupt > > <...>-550 90d.Z. 8us : rcu_nmi_enter <-soft_nmi_interrupt > > <...>-550 90d.Z. 9us : rcu_nmi_exit <-soft_nmi_interrupt > > <...>-550 90d... 9us : printk_nmi_exit <-soft_nmi_interrupt > > <...>-550 90d... 10us : cpuacct_charge <-update_curr_rt > > > > Set the decrementer pending in the irq_happened mask directly, rather > > than having the masked decrementer handler do it. > > Setting the paca field needs hard irqs off... Doh! Good catch, I should have noticed that :) > also preempt_disable > doesn't look necessary if IRQs are off. True, just copied from existing code. Thanks, Nick
