From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfram Sang Subject: Re: [PATCH] i2c: core: Prevent race condition when removing i2c devices Date: Mon, 31 Jul 2017 15:38:14 +0200 Message-ID: <20170731133814.b5lyujdl5iwhcalx@ninjato> References: <20170608024344.9311-1-david.thomson@alliedtelesis.co.nz> <20170619143656.zigxk77vegedscjx@ninjato> <24ee1e30-1737-e3ef-a23e-01d41a29d45f@axentia.se> <2e4c5807-3d3c-1ce2-da35-3e37b2e3b08b@axentia.se> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="klaquncw2eqqdmau" Return-path: Received: from sauhun.de ([88.99.104.3]:49300 "EHLO pokefinder.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751054AbdGaNiP (ORCPT ); Mon, 31 Jul 2017 09:38:15 -0400 Content-Disposition: inline In-Reply-To: <2e4c5807-3d3c-1ce2-da35-3e37b2e3b08b@axentia.se> Sender: linux-i2c-owner@vger.kernel.org List-Id: linux-i2c@vger.kernel.org To: Peter Rosin Cc: David Thomson , linux-i2c@vger.kernel.org --klaquncw2eqqdmau Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Mon, Jun 19, 2017 at 09:30:06PM +0200, Peter Rosin wrote: > On 2017-06-19 18:34, Peter Rosin wrote: > > It would certainly be nice to know why .owner is clobbered, because I > > don't see it. But then again, I don't know what sources I should be > > reading... > > BTW, one thing I noticed when reading the current code is that I see this > at the end of i2c_del_adapter: > > /* Clear the device structure in case this adapter is ever going to be > added again */ > memset(&adap->dev, 0, sizeof(adap->dev)); > } > EXPORT_SYMBOL(i2c_del_adapter); It was added with commit bd4bc3dbded9cd ("i2c: Clear i2c_adapter.dev on adapter removal") with this commit message: i2c: Clear i2c_adapter.dev on adapter removal Clear i2c_adapter.dev on adapter removal. This makes it possible to re-add the adapter at a later point, which some drivers (i2c-amd756-s4882, i2c-nforce2-s4985) actually do. This fixes a bug reported by John Stultz here: http://lkml.org/lkml/2008/7/15/720 and by Ingo Molar there: http://lkml.org/lkml/2008/7/16/78 So, despite the docs, it used to be an issue actually... --klaquncw2eqqdmau Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEOZGx6rniZ1Gk92RdFA3kzBSgKbYFAll/MsYACgkQFA3kzBSg KbaORA/9GRW1nkvbk3TQ5+sv3fovuXUUQlZtvJ8Bqtwx7bFzwNKytzoVjrFhFlIX 0gHWCwlwYt7qCM5JmTxSuXOIZRiVbIsByObwrJGoYRKeLYNSD4E+gVTfqT/DZqWZ MFCV4KhR+GeTiINWNZsl+GJVUJNAY9OeFUKa3ftjBz7eMoU0OG4JEt0mdUp2Y0WD OI32Gb8dbEcDPCCnG36j1v2ob+q0NL7hziySpOoIcVn1cmn8YW0nmQVsfXpbH5b6 7E/S9pbRSk3rYJ9SdaIuoSFGE2NrOh3Gao6uAUUVnzg0GaPhT7dGeN2QtldwXTYR jBEBO0fn9gstDP0dulpjjwimTvGRyFoh0a50KVcKvIKEs299/UBIFo2xy9C3tlJp XYXz4ZaI2BMCiunndSkIiyNpql6/mhRZstIuEh27M6Kqh0+pTym/9xn5wREHXsva QICZjg52pcWavKvCe6RLb2XluyfFgSm/C+BmKKajX1JDA0v90wpRi8xtsQhXp0t7 KG7FL2988/CnCi3Nmptwa2uiG3wt3VtfGblM4f6Zn4NpHMoD/GnB+pNBaTu2MA4n pdawQjnaVgjSSkBsmYBfZyi5Kan5cFPxTo6brHVCjMVnZKOVC3GhtU3qtdXRD1R3 7idIwBfMCT+z2eLPw7m1T3YPJFxa/fIEwEyavFOZwHxkwL0s3+I= =7E55 -----END PGP SIGNATURE----- --klaquncw2eqqdmau--