From: Pavel Machek <pavel@ucw.cz>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
johannes.berg@intel.com
Cc: linux-leds@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] leds: trigger: Disable CPU trigger on PREEMPT_RT
Date: Mon, 27 Sep 2021 16:23:45 +0200 [thread overview]
Message-ID: <20210927142345.GB18276@duo.ucw.cz> (raw)
In-Reply-To: <20210924111501.m57cwwn7ahiyxxdd@linutronix.de>
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Hi!
> 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.
Can you take a look at:
Subject: [PATCH] leds: trigger: use RCU to protect the led_cdevs list
From: Johannes Berg <johannes.berg@intel.com>
It changes affected area, and there's good chance RCU solves your
problem. (And you may be better person to review it than I am).
I'll apply Johanness' patch to the -next, and see what happens. If
someone sees a problem, speak up.
Best regards,
Pavel
--
http://www.livejournal.com/~pavelmachek
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next prev parent reply other threads:[~2021-09-27 14:23 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 [this message]
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
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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