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=-8.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 54DABC4338F for ; Wed, 18 Aug 2021 11:58:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2969960462 for ; Wed, 18 Aug 2021 11:58:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233895AbhHRL6g (ORCPT ); Wed, 18 Aug 2021 07:58:36 -0400 Received: from mail.kernel.org ([198.145.29.99]:40800 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231476AbhHRL6e (ORCPT ); Wed, 18 Aug 2021 07:58:34 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 3A4FD60F35; Wed, 18 Aug 2021 11:57:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1629287879; bh=zDdIEBXge4nz0nnU4dADmgnRlRa8EXpkrmPjAb2TLGY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=is+3SKOxJmzcnOtFScFhV4MIyK5peo6X99sk7V3/q/hLKtn8cUmsLsMrJWv7SxYKg r6EDlZJ4nS4G1LhKOUFE+pgOX9q1ufy1RmDiTAC9if3j9rcRCd4LnYlbfIbcPd/VXe eLui6X9ld6D7TCrAwPti41uXTSzpnlltAO8ZVEVbxeJGs/++FR95FgMV6BUjHBewP7 1p53QfnanSr2jdQrlEYF/qZ8vYqyD+w+Q47L9NNtOz+FI4ehvEuieDdex1dm0EgQiC 7ATJ8obp9FxX/R2dMLDE+7l9kkt/MijPqxQB4WB99dbAHg2OB4Z7v7+DDXarnB/sMy HW2JxkJOwXecg== Date: Wed, 18 Aug 2021 12:57:36 +0100 From: Mark Brown To: Greg Kroah-Hartman Cc: Pierre-Louis Bossart , alsa-devel@alsa-project.org, tiwai@suse.de, vkoul@kernel.org, liam.r.girdwood@linux.intel.com, Andy Shevchenko , Dan Williams , Jason Gunthorpe , Christoph Hellwig , "Rafael J . Wysocki" , linux-kernel@vger.kernel.org, Geert Uytterhoeven Subject: Re: [RFC PATCH 1/2] driver core: export driver_deferred_probe_trigger() Message-ID: <20210818115736.GA4177@sirena.org.uk> References: <20210817190057.255264-1-pierre-louis.bossart@linux.intel.com> <20210817190057.255264-2-pierre-louis.bossart@linux.intel.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="AhhlLboLdkugWU4S" Content-Disposition: inline In-Reply-To: X-Cookie: She sells cshs by the cshore. User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --AhhlLboLdkugWU4S Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Aug 18, 2021 at 07:44:39AM +0200, Greg Kroah-Hartman wrote: > On Tue, Aug 17, 2021 at 02:00:56PM -0500, Pierre-Louis Bossart wrote: > > In these cases, there is no way to notify the deferred probe > > infrastructure of the enablement of resources after the driver > > binding. > Then just wait for it to happen naturally? Through what mechanism will it happen naturally? Deferred probe currently only does things if things are being registered or if probes complete. > > The driver_deferred_probe_trigger() function is currently used > > 'anytime a driver is successfully bound to a device', this patch > > suggest exporing by exporting it so that drivers can kick-off > > re-probing of deferred devices at the end of a deferred processing. > I really do not want to export this as it will get really messy very > quickly with different drivers/busses attempting to call this. I'm not sure I see the mess here - it's just queueing some work, one of the things that the workqueue stuff does well is handle things getting scheduled while they're already queued. Honestly having understood their problem I think we need to be adding these calls into all the resource provider APIs. > Either handle it in your driver (why do you have to defer probe at all, > just succeed and move on to register the needed stuff after you are > initialized) or rely on the driver core here. That's exactly what they're doing currently and the driver core isn't delivering. Driver A is slow to start up and providing a resource to driver B, this gets handled in driver A by succeeding immediately and then registering the resource once the startup has completed. Unfortunately while that was happening not only has driver B registered and deferred but the rest of the probes/defers in the system have completed so the deferred probe mechanism is idle. Nothing currently tells the deferred probe mechanism that a new resource is now available so it never retries the probe of driver B. The only way I can see to fix this without modifying the driver core is to make driver A block during probe but that would at best slow down boot. The issue is that the driver core is using drivers completing probe as a proxy for resources becoming available. That works most of the time because most probes are fully synchronous but it breaks down if a resource provider registers resources outside of probe, we might still be fine if system boot is still happening and something else probes but only through luck. --AhhlLboLdkugWU4S Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAABCgAdFiEEreZoqmdXGLWf4p/qJNaLcl1Uh9AFAmEc9a8ACgkQJNaLcl1U h9BeUgf/bxaKOZOoIjNrTdjgfaEekt/IY0d7bcnHylKh/CMn3PK4hhYyUa2i3cIr SMe2P9NrdsU/EpaqvHGE1QL6v09OsT5n0TzHJ75cHzcC6qkjasu7ble9AubIQKcy Fw1VYQa7GzzvR7WPZtyEKN/XHCluIc9/LBQ5Wuze5cwONg2EQRMsY9f0rMOD3h+9 2VFtykn+/BK/42dDs9Oese4TRAifzF2P8/jN3oFIk1/oSBldu6+eod38HDIK5HNc IY1MKq26TIdUjtnK1aa8X0dMPE4+p6scHbqilxi2ILutzuRpW5D4OPouptCghSkq YJgZEEba8o28TT8sJCorZorZf34EwQ== =FeUe -----END PGP SIGNATURE----- --AhhlLboLdkugWU4S--