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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 65A4FC433DF for ; Tue, 30 Jun 2020 15:39:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3939020760 for ; Tue, 30 Jun 2020 15:39:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593531545; bh=5ayWs9imhyx142bbxrkjgUqDHZEo9tanWvglgpNeTyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=ANyx//+SAPSIdw1cAbl9HulTjfDwwyMQ39AbY1dhCbdeDgezwHTZ3k3xqelIo4ywN ++i+DNrO/wS89Bz4kqar6bBVpgti+wNuYWVEs+m5l6WObdmvHY7bbLdYrmMytIKMfg XuoXOF2IrG9+qjyzCpKe7G4OI07RFmSn6e424opE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389585AbgF3PjE (ORCPT ); Tue, 30 Jun 2020 11:39:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:33828 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389551AbgF3PjD (ORCPT ); Tue, 30 Jun 2020 11:39:03 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D173E2074F; Tue, 30 Jun 2020 15:39:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1593531542; bh=5ayWs9imhyx142bbxrkjgUqDHZEo9tanWvglgpNeTyw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=hIoVkegTJbblSoTaWmEWSOjjChWYsIljeAxfKj0C68W37DzgU+2dPK3VrudtDS50U sSZQmrWNEf6yuGaV+SdPNAuEdUyGKB6NycC4g1MRydwtjKbV/6QjSgXHIKs7tm1p1r Hm397WUXg/TZ1y4/sDoVPM/qEQuRDNdNYT0Ar5Po= Date: Tue, 30 Jun 2020 17:38:50 +0200 From: Greg Kroah-Hartman To: "Rafael J. Wysocki" Cc: Geert Uytterhoeven , Saravana Kannan , "Cc: Android Kernel" , "Rafael J. Wysocki" , Linux Kernel Mailing List Subject: Re: [PATCH v1] driver core: Fix suspend/resume order issue with deferred probe Message-ID: <20200630153850.GE1785141@kroah.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 30, 2020 at 03:50:58PM +0200, Rafael J. Wysocki wrote: > On Fri, Jun 26, 2020 at 10:53 PM Geert Uytterhoeven > wrote: > > > > Hi Saravana, > > > > On Fri, Jun 26, 2020 at 10:34 PM Saravana Kannan wrote: > > > On Fri, Jun 26, 2020 at 4:27 AM Rafael J. Wysocki wrote: > > > > On Thu, Jun 25, 2020 at 7:52 PM Saravana Kannan wrote: > > > > > On Thu, Jun 25, 2020 at 10:47 AM Rafael J. Wysocki wrote: > > > > > > Note that deferred probing gets in the way here and so the problem is > > > > > > related to it. > > > > > > > > > > I mean, we officially support deferred probing. Shouldn't we fix it so > > > > > that it doesn't break suspend/resume? > > > > > > > > Yes, we should fix deferred probing. > > > > Please take into account that breakage is an actual regression. > > > > > > > Also, it's pretty easy to have > > > > > cases where one module probes multiple device instances and loading it > > > > > in one order would break dpm_list order for one device and loading it > > > > > in another order would break it for another device. And there would be > > > > > no "proper" order to load modules (because module order != device > > > > > order). > > > > > > > > I'm not saying that the current code is perfect. I'm saying that the > > > > fix as proposed adds too much cost for everybody who may not care IMO. > > > > > > Ok, how about I don't do this reordering until we see the first > > > deferred probe request? Will that work for you? In that case, systems > > > with no deferred probing will not incur any reordering cost. Or if > > > reordering starts only towards the end, all the previous probes won't > > > incur reordering cost. > > > > That first deferred probe request is more or less as of the first probe, > > since commit 93d2e4322aa74c1a ("of: platform: Batch fwnode parsing when > > adding all top level devices"), at least on DT systems. > > The deferred probe reordering of devices to the end of dpm_list > started in 2012, so it is nothing new, and it demonstrably works for > devices where the dependencies are known to the driver core. > > That said, in the cases when the dependencies are known to the driver > core, it is also unnecessary to reorder dpm_list in > deferred_probe_work_func(), because the right ordering of it is going > to be determined elsewhere. > > Also commit 494fd7b7ad10 ("PM / core: fix deferred probe breaking > suspend resume order") is not the source of the problem here, because > the problem would have still been there without it, due to the > device_pm_move_last() that was there before, so the Fixes: tag > pointing to that commit is misleading. > > Now, because 716a7a259690 ("driver core: fw_devlink: Add support for > batching fwnode parsing") is an optimization and the regression is > present because of it AFAICS, the best way to address it at that point > would be to revert commit 716a7a259690 for 5.8 and maybe do the > optimization more carefully. > > Greg, what do you think? I've been ignoreing this and letting you all sort it out :) But if you think that patch should be reverted, I'll not object and will be glad to to it if this solves the issue. thanks, greg k-h