On Mon 2021-09-27 17:35:02, Thomas Gleixner wrote:
> Pavel,
> 
> On Mon, Sep 27 2021 at 16:23, Pavel Machek wrote:
> >
> >> The CPU trigger is invoked on ARM from CPU-idle. That trigger later
> >> invokes led_trigger_event() which acquires a read lock in an IRQ-off
> >> section. The problematic part on PREEMPT_RT is that this lock is turned
> >> into a sleeping lock and must not be acquired with disabled interrupts.
> >> 
> >> The problem continues as that the LED driver underneath must not acquire
> >> any sleeping locks itself.
> >> 
> >> Disable the CPU trigger on PREEMPT_RT.
> >
> > I know locking with leds is problematic, but I believe you'll hit
> > similar problem elsewhere... Disabling triggers is not solution.
> 
> Disabling stuff which is not working well with RT is very much a
> solution in order to make progress.
> 
> We have surely more essential problems to solve than making leds blink
> and if anyone cares enough about them, then this can be worked on in
> parallel. That has been disabled on RT for ever and so far nobody
> complained or cared enough about it.

Would you mind reading and responding to the rest of the email?

I'm not applying this.
								Pavel
-- 
http://www.livejournal.com/~pavelmachek