From: Pavel Machek <pavel@ucw.cz>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@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 21:06:50 +0200 [thread overview]
Message-ID: <20210927190650.GA13992@duo.ucw.cz> (raw)
In-Reply-To: <20210927171802.uak3tbpqaig3mm7m@linutronix.de>
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Hi!
> > Would you mind reading and responding to the rest of the email?
>
> The patch you mentioned,
> https://https://lkml.kernel.org/r/.kernel.org/all/20210915181601.99a68f5718be.I1a28b342d2d52cdeeeb81ecd6020c25cbf1dbfc0@changeid/
>
> would remove the lock from led_trigger_event().
> Are there any guarantees how many callbacks maybe invoked and what kind
> of locks may be acquired?
These kind of functions should not sleep other than that, there are no
restrictions AFAICT.
Other triggers are relying on that non-sleeping assumption.
> Leaving kworker usage aside there are still things like spinlock_t usage
> in input_leds_brightness_set(), nic78bx_brightness_set() (from a quick
> grep) which have the same problems.
>
> > I'm not applying this.
>
> I hope you reconsider. It is not all LED usage, just the CPU
> trigger.
What makes the CPU trigger special with RT? Other triggers will be
called from interesting places, too... Johanes pointed out other
problems with that rwlock, and we are getting rid of the rwlock.
Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek
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next prev parent reply other threads:[~2021-09-27 19:06 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
2021-09-27 17:18 ` Sebastian Andrzej Siewior
2021-09-27 17:36 ` Johannes Berg
2021-09-27 19:06 ` Pavel Machek [this message]
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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