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
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