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=-2.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_NEOMUTT autolearn=ham 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 A582CECDFB0 for ; Thu, 12 Jul 2018 21:28:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 60B042087C for ; Thu, 12 Jul 2018 21:28:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 60B042087C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=the-dreams.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733105AbeGLVkT (ORCPT ); Thu, 12 Jul 2018 17:40:19 -0400 Received: from sauhun.de ([88.99.104.3]:59974 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733084AbeGLVkT (ORCPT ); Thu, 12 Jul 2018 17:40:19 -0400 Received: from localhost (p5486CFAA.dip0.t-ipconnect.de [84.134.207.170]) by pokefinder.org (Postfix) with ESMTPSA id 73672574612; Thu, 12 Jul 2018 23:28:51 +0200 (CEST) Date: Thu, 12 Jul 2018 23:28:51 +0200 From: Wolfram Sang To: Peter Rosin Cc: linux-kernel@vger.kernel.org, Peter Huewe , Jarkko Sakkinen , Jason Gunthorpe , Arnd Bergmann , Greg Kroah-Hartman , Brian Norris , Gregory Fong , Florian Fainelli , bcm-kernel-feedback-list@broadcom.com, Sekhar Nori , Kevin Hilman , Haavard Skinnemoen , Kukjin Kim , Krzysztof Kozlowski , Orson Zhai , Baolin Wang , Chunyan Zhang , Guenter Roeck , Crt Mori , Jonathan Cameron , Hartmut Knaack , Lars-Peter Clausen , Peter Meerwald-Stadler , Dmitry Torokhov , Antti Palosaari , Mauro Carvalho Chehab , Michael Krufky , Lee Jones , linux-integrity@vger.kernel.org, linux-i2c@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, linux-iio@vger.kernel.org, linux-input@vger.kernel.org, linux-media@vger.kernel.org Subject: Re: [PATCH v2 00/10] Split i2c_lock_adapter into i2c_lock_root and i2c_lock_segment Message-ID: <20180712212850.axi3rrfwivqymqh5@ninjato> References: <20180620051803.12206-1-peda@axentia.se> <20180626023735.xj7aqhvw7ta2lq6s@ninjato> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="x66e45tdlj2g4bta" Content-Disposition: inline In-Reply-To: <20180626023735.xj7aqhvw7ta2lq6s@ninjato> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --x66e45tdlj2g4bta Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Jun 26, 2018 at 11:37:36AM +0900, Wolfram Sang wrote: > On Wed, Jun 20, 2018 at 07:17:53AM +0200, Peter Rosin wrote: > > Hi! > >=20 > > With the introduction of mux-locked I2C muxes, the concept of > > locking only a segment of the I2C adapter tree was added. At the > > time, I did not want to cause a lot of extra churn, so left most > > users of i2c_lock_adapter alone and apparently didn't think enough > > about it; they simply continued to lock the whole adapter tree. > > However, i2c_lock_adapter is in fact wrong for almost every caller > > (there is naturally an exception) that is itself not a driver for > > a root adapter. What normal drivers generally want is to only > > lock the segment of the adapter tree that their device sits on. > >=20 > > In fact, if a device sits behind a mux-locked I2C mux, and its > > driver calls i2c_lock_adapter followed by an unlocked I2C transfer, > > things will deadlock (since even a mux-locked I2C adapter will lock > > its parent at some point). If the device is not sitting behind a > > mux-locked I2C mux (i.e. either directly on the root adapter or > > behind a (chain of) parent-locked I2C muxes) the root/segment > > distinction is of no consequence; the root adapter is locked either > > way. > >=20 > > Mux-locked I2C muxes are probably not that common, and putting any > > of the affected devices behind one is probably even rarer, which > > is why we have not seen any deadlocks. At least not that I know > > of... > >=20 > > Since silently changing the semantics of i2c_lock_adapter might > > be quite a surprise, especially for out-of-tree users, this series > > instead removes the function and forces all users to explicitly > > name I2C_LOCK_SEGMENT or I2C_LOCK_ROOT_ADAPTER in a call to > > i2c_lock_bus, as suggested by Wolfram. Yes, users will be a teensy > > bit more wordy, but open-coding I2C locking from random drivers > > should be avoided, so it's perhaps a good thing if it doesn't look > > too neat? > >=20 > > I suggest that Wolfram takes this series through the I2C tree and > > creates an immutable branch for the other subsystems. The series > > is based on v4.18-r1. >=20 > Applied to a seperate branch named "i2c/precise-locking-names" which I > will merge into for-next, so it will get proper testing already. Once we > get the missing acks from media, MFD, and IIO maintainers, I will merge > it into for-4.19. Ping for media related acks. Thanks, Wolfram --x66e45tdlj2g4bta Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAltHyA4ACgkQFA3kzBSg KbZ2HhAAjghhfIxl1PUVt0HWyAG9QvpZUyd/pnXG1rS1R5Ho2LBck9bTQygMLbt2 EjLyMlpLpBTNLIG3eMmsLQY5IN5TisTG72jBrfFk6bj6M9pe1Cv9y9rRwQajKdwH 3Zkppsx+FXVoopq2HqOp9RgGR3srJV+kHzpkPg23tgXoKhMmpSb7qxxk8YnCaMcF 3cU31OC1BF7GrhmhI5RpJyDOc1td7gfJjLWjfUjtj+r9gQPGvvPeB4WwV/agtFRh TDARV2YNPuvt1+1CkQ4tuowOrBeGB8qtlP9jm1+HcyxejVBbVzEXS27R7Afw6t2d ZY7Wkq4U+KB0JCgZ+VS5O6Q3g8F0nUUqADBNxDnkH9Vbj/Eshn9+oMQUWjn6D7my XkEHJnUlwSf4+lN5NvUUwOjNrbG7HhogY0+6fDWgg01eibnfK017SWQm0VHgmb1X EJIL1CMjBdlLJfCATrndShKwJIQRZmLsARZFmj+94Run5gD7bdZzMeO3CCp8Faly NZSNeOjGEqFKFX04vmh9zNiJDo/fxMzOPd8cB71pFidYXn6DtkoZyyD74XcZExtz 5aAEBjKKUnZ79hO66oTLwQhiaORP4obH5M+yrlzOacTLIYhww+G7QGJdMdndX6zO A2j8aCnxOVxr9Di8Pk+DXJOiskU/TyKCQeT49UdT94cSpc4r6IM= =4bN7 -----END PGP SIGNATURE----- --x66e45tdlj2g4bta--