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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5DFA9C433E1 for ; Wed, 24 Mar 2021 11:28:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 36511619F3 for ; Wed, 24 Mar 2021 11:28:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229839AbhCXL2V (ORCPT ); Wed, 24 Mar 2021 07:28:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38446 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235262AbhCXL1B (ORCPT ); Wed, 24 Mar 2021 07:27:01 -0400 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1FF42C0613E3 for ; Wed, 24 Mar 2021 04:26:33 -0700 (PDT) Received: from ptx.hi.pengutronix.de ([2001:67c:670:100:1d::c0]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1lP1ef-0000BZ-4o; Wed, 24 Mar 2021 12:26:29 +0100 Received: from ukl by ptx.hi.pengutronix.de with local (Exim 4.92) (envelope-from ) id 1lP1ee-0001xW-Ih; Wed, 24 Mar 2021 12:26:28 +0100 Date: Wed, 24 Mar 2021 12:26:26 +0100 From: Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= To: Johan Hovold Cc: Sebastian Andrzej Siewior , Greg Kroah-Hartman , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Sam Nobs , Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH] serial: imx: drop workaround for forced irq threading Message-ID: <20210324112626.iqteqgfbkci3xmvh@pengutronix.de> References: <20210322111036.31966-1-johan@kernel.org> <20210322113402.naqzgkoe2xesnw4b@pengutronix.de> <20210322113918.ze52gq54cpsspgej@linutronix.de> <20210322115536.knkea7i6vrfpotol@pengutronix.de> <20210322134032.kmirudtnkd4akkgu@pengutronix.de> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="zi5o6fqsy3kf62o4" Content-Disposition: inline In-Reply-To: X-SA-Exim-Connect-IP: 2001:67c:670:100:1d::c0 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --zi5o6fqsy3kf62o4 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Johan, On Tue, Mar 23, 2021 at 03:37:29PM +0100, Johan Hovold wrote: > On Mon, Mar 22, 2021 at 02:40:32PM +0100, Uwe Kleine-K=F6nig wrote: > > On Mon, Mar 22, 2021 at 02:20:57PM +0100, Johan Hovold wrote: > > > On Mon, Mar 22, 2021 at 12:55:36PM +0100, Uwe Kleine-K=F6nig wrote: > > > > On Mon, Mar 22, 2021 at 12:39:18PM +0100, Sebastian Andrzej Siewior= wrote: > > > > > On 2021-03-22 12:34:02 [+0100], Uwe Kleine-K=F6nig wrote: > > > > > > On Mon, Mar 22, 2021 at 12:10:36PM +0100, Johan Hovold wrote: > > > > > > > Force-threaded interrupt handlers used to run with interrupts= enabled, > > > > > > > something which could lead to deadlocks in case a threaded ha= ndler > > > > > > > shared a lock with code running in hard interrupt context (e.= g. timer > > > > > > > callbacks) and did not explicitly disable interrupts. > > > > > > >=20 > > > > > > > This was specifically the case for serial drivers that take t= he port > > > > > > > lock in their console write path as printk can be called from= hard > > > > > > > interrupt context also with forced threading ("threadirqs"). > > > > > > >=20 > > > > > > > Since commit 81e2073c175b ("genirq: Disable interrupts for fo= rce > > > > > > > threaded handlers") interrupt handlers always run with interr= upts > > > > > > > disabled on non-RT so that drivers no longer need to do handl= e this. > > > > > >=20 > > > > > > So we're breaking RT knowingly here? If this is the case I'm no= t happy > > > > > > with your change. (And if RT is not affected a different wordin= g would > > > > > > be good.) > > > > >=20 > > > > > Which wording, could you be more specific? It looks good from her= e and > > > > > no, RT is not affected. > > > >=20 > > > > The commit log says essentially: "The change is fine on non-RT" whi= ch > > > > suggests there is a problem on RT. > > >=20 > > > I don't think you can read that into the commit message. > >=20 > > From a strictly logically point of view you indeed cannot. But if you go > > to the street and say to people there that they can park their car in > > this street free of charge between Monday and Friday, I expect that most > > of them will assume that they have to pay for parking on weekends. >=20 > That analogy would almost seem to suggest bad intent on my side. That analogy's purpose was to put over my point that writing (paraphrased) "Since non-RT changed, this workaround isn't necessary any more" suggests to me that the change might be bad for RT. So again, there was no harm intended, this is just a call for clearing up either the commit log to make it obvious the change is right or to fix the problem on RT if there is any. > To say that this workaround is no longer needed on !RT does not imply > that it is needed on RT. If anything it suggests I have considered RT, > I'd say. The code in question was used for both RT and non-RT. You drop it for both cases and only justify one of them. OK, fine, you considered both cases. Just from reading the commit log I considered you didn't. It's completely ok for me to be wrong here, but I still think the chosen words are not optimal and stumbling as I did is easy. So I still see a potential to improve the wording. Best regards Uwe --=20 Pengutronix e.K. | Uwe Kleine-K=F6nig | Industrial Linux Solutions | https://www.pengutronix.de/ | --zi5o6fqsy3kf62o4 Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEfnIqFpAYrP8+dKQLwfwUeK3K7AkFAmBbId8ACgkQwfwUeK3K 7AmrPQf/ddQwQ54O9l7xV1/XHw8vOIwucKKyjYQahAx40PXG3l82aSNYFbEm2naq Skuiv/ZUYkuFgJplG45b5lSQCplanZ29bpfJJA6umGqNLU26U77BbscwG6Rw6DC0 uJ6764kmQcQXgp9gn8+IAZUlmVw4FReNdvJcLqKgsU2Q1XUyoUAbLW8cF5Ijqliq 5KvWHZcVw6srh3zGo1YYDqIWEfnyB/y18tcSrD5ywaGS6heFxJXNOeucvm2IxDZQ 0dNLzqJuruItdbPN1foj3zaZwSQozrqhXkn81z0XG4H02ub7lkYPNjG9PE3095EI hkuQ8I5b5VWjg5BwyMY5QjbhtjSeOA== =Tj6B -----END PGP SIGNATURE----- --zi5o6fqsy3kf62o4--