From: Pavel Machek <pavel@ucw.cz>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
johannes.berg@intel.com, linux-leds@vger.kernel.org
Subject: Re: [PATCH] leds: trigger: Disable CPU trigger on PREEMPT_RT
Date: Mon, 27 Sep 2021 17:44:51 +0200 [thread overview]
Message-ID: <20210927154451.GA17112@duo.ucw.cz> (raw)
In-Reply-To: <87wnn2av6h.ffs@tglx>
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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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next prev parent reply other threads:[~2021-09-27 15:44 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-24 11:15 [PATCH] leds: trigger: Disable CPU trigger on PREEMPT_RT Sebastian Andrzej Siewior
2021-09-27 14:23 ` Pavel Machek
2021-09-27 15:35 ` Thomas Gleixner
2021-09-27 15:44 ` Pavel Machek [this message]
2021-09-27 17:18 ` Sebastian Andrzej Siewior
2021-09-27 17:36 ` Johannes Berg
2021-09-27 19:06 ` Pavel Machek
2021-09-27 19:34 ` Sebastian Andrzej Siewior
2021-10-13 8:08 ` Pavel Machek
2021-10-13 8:39 ` Sebastian Andrzej Siewior
2021-10-13 8:42 ` Pavel Machek
2021-10-13 9:08 ` Sebastian Andrzej Siewior
2021-10-13 9:37 ` [PATCH v2] " Sebastian Andrzej Siewior
2021-10-13 18:08 ` Pavel Machek
2021-09-28 0:14 ` [PATCH] " Thomas Gleixner
2021-09-27 18:48 ` Thomas Gleixner
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