From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AEDFAC433EF for ; Mon, 27 Sep 2021 15:44:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9286960F3A for ; Mon, 27 Sep 2021 15:44:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235132AbhI0Pqa (ORCPT ); Mon, 27 Sep 2021 11:46:30 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:35636 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234500AbhI0Pqa (ORCPT ); Mon, 27 Sep 2021 11:46:30 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 6E5D21C0B7A; Mon, 27 Sep 2021 17:44:51 +0200 (CEST) Date: Mon, 27 Sep 2021 17:44:51 +0200 From: Pavel Machek To: Thomas Gleixner Cc: Sebastian Andrzej Siewior , johannes.berg@intel.com, linux-leds@vger.kernel.org Subject: Re: [PATCH] leds: trigger: Disable CPU trigger on PREEMPT_RT Message-ID: <20210927154451.GA17112@duo.ucw.cz> References: <20210924111501.m57cwwn7ahiyxxdd@linutronix.de> <20210927142345.GB18276@duo.ucw.cz> <87wnn2av6h.ffs@tglx> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="LQksG6bCIzRHxTLp" Content-Disposition: inline In-Reply-To: <87wnn2av6h.ffs@tglx> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org --LQksG6bCIzRHxTLp Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon 2021-09-27 17:35:02, Thomas Gleixner wrote: > Pavel, >=20 > 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. > >>=20 > >> The problem continues as that the LED driver underneath must not acqui= re > >> any sleeping locks itself. > >>=20 > >> 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. >=20 > Disabling stuff which is not working well with RT is very much a > solution in order to make progress. >=20 > 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 --=20 http://www.livejournal.com/~pavelmachek --LQksG6bCIzRHxTLp Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iF0EABECAB0WIQRPfPO7r0eAhk010v0w5/Bqldv68gUCYVHm8wAKCRAw5/Bqldv6 8mh9AJ4isoGzeo9/2ZlppxWei3SDG7SsjACggn5kQQUjHouzpkDO1QsNq8pH3g4= =SoI1 -----END PGP SIGNATURE----- --LQksG6bCIzRHxTLp--