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=-6.3 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=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 5E51EC4363C for ; Wed, 7 Oct 2020 08:14:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5ED920870 for ; Wed, 7 Oct 2020 08:14:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602058445; bh=G6wo9pRH97NvVw3CieOpfHR9XdQR26XJkAPylVPt2tA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=QPMHujeg4wGUxZnE+qFbSdHYycNZuBJ+EPSwvk2qQ1VILDzVRfuDi+hj+MLKTI5NI dmi+UDYKZQ5drz08Wu1q/EM2gwq26NMmPQ/r/Cb4nD13vnwPlAmbRr75CKWR1pDPLN fCw0SKSROZMSP38yzo68tG2o9CJAUX8GLIRqimhA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727558AbgJGIOE (ORCPT ); Wed, 7 Oct 2020 04:14:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:35578 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725976AbgJGIOE (ORCPT ); Wed, 7 Oct 2020 04:14:04 -0400 Received: from pali.im (pali.im [31.31.79.79]) (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 41CBB2076C; Wed, 7 Oct 2020 08:14:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1602058443; bh=G6wo9pRH97NvVw3CieOpfHR9XdQR26XJkAPylVPt2tA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kj8+eaKiCxKooT7aHfCi18I6OkpyQmWSDLq6PbSjhW9ufLJGdvMkgx66f8Zist++X lTLK0/v+r0ZIS1CmjSPnPJFJtId6qMPsuwC1UXbPal60EEPVC495wq1vbStQcsAUjy Fwx2yXpkc7vUCOkys3zSTO6JddWOP5iPs02wQuC8= Received: by pali.im (Postfix) id DFF224F1; Wed, 7 Oct 2020 10:14:00 +0200 (CEST) Date: Wed, 7 Oct 2020 10:14:00 +0200 From: Pali =?utf-8?B?Um9ow6Fy?= To: Oliver O'Halloran Cc: Bjorn Helgaas , Bjorn Helgaas , linux-pci , Linux Kernel Mailing List , Lorenzo Pieralisi , Gregory Clement , Andrew Lunn , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Yinghai Lu Subject: Re: PCI: Race condition in pci_create_sysfs_dev_files Message-ID: <20201007081400.tmoisrk2be5gkkhh@pali> References: <20200909112850.hbtgkvwqy2rlixst@pali> <20201006222222.GA3221382@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wednesday 07 October 2020 12:47:40 Oliver O'Halloran wrote: > On Wed, Oct 7, 2020 at 10:26 AM Bjorn Helgaas wrote: > > > > I'm not really a fan of this because pci_sysfs_init() is a bit of a > > hack to begin with, and this makes it even more complicated. > > > > It's not obvious from the code why we need pci_sysfs_init(), but > > Yinghai hinted [1] that we need to create sysfs after assigning > > resources. I experimented by removing pci_sysfs_init() and skipping > > the ROM BAR sizing. In that case, we create sysfs files in > > pci_bus_add_device() and later assign space for the ROM BAR, so we > > fail to create the "rom" sysfs file. > > > > The current solution to that is to delay the sysfs files until > > pci_sysfs_init(), a late_initcall(), which runs after resource > > assignments. But I think it would be better if we could create the > > sysfs file when we assign the BAR. Then we could get rid of the > > late_initcall() and that implicit ordering requirement. > > You could probably fix that by using an attribute_group to control > whether the attribute shows up in sysfs or not. The .is_visible() for > the group can look at the current state of the device and hide the rom > attribute if the BAR isn't assigned or doesn't exist. That way we > don't need to care when the actual assignment occurs. And cannot we just return e.g. -ENODATA (or other error code) for those problematic sysfs nodes until late_initcall() is called? > > But I haven't tried to code it up, so it's probably more complicated > > than this. I guess ideally we would assign all the resources before > > pci_bus_add_device(). If we could do that, we could just remove > > pci_sysfs_init() and everything would just work, but I think that's a > > HUGE can of worms. > > I was under the impression the whole point of pci_bus_add_device() was > to handle any initialisation that needed to be done after resources > were assigned. Is the ROM BAR being potentially unassigned an x86ism > or is there some bigger point I'm missing? > > Oliver