On Sat, May 15, 2021 at 01:23:02AM +0200, Thomas Gleixner wrote:
> We can make that work but sure I'm not going to argue when you decide to
> just go for raise_softirq_irqsoff().
>
> I just hacked that check up which is actually useful beyond NAPI. It's
> straight forward except for that flush_smp_call_function_from_idle()
> oddball, which immeditately triggered that assert because block mq uses
> __raise_softirq_irqsoff() in a smp function call...
>
> See below. Peter might have opinions though :)
Yeah, lovely stuff :-)
> +#define lockdep_assert_softirq_raise_ok() \
> +do { \
> + WARN_ON_ONCE(__lockdep_enabled && \
> + !current->softirq_raise_safe && \
> + !(softirq_count() | hardirq_count())); \
> +} while (0)
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -691,7 +691,9 @@ void flush_smp_call_function_from_idle(v
> cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU,
> smp_processor_id(), CFD_SEQ_IDLE);
> local_irq_save(flags);
> + lockdep_set_softirq_raise_safe();
> flush_smp_call_function_queue(true);
> + lockdep_clear_softirq_raise_safe();
> if (local_softirq_pending())
> do_softirq();
I think it might make more sense to raise hardirq_count() in/for
flush_smp_call_function_queue() callers that aren't already from hardirq
context. That's this site and smpcfd_dying_cpu().
Then we can do away with this new special case.
