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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B6B31C433FE for ; Thu, 30 Sep 2021 15:04:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D90F619E2 for ; Thu, 30 Sep 2021 15:04:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239842AbhI3PFt (ORCPT ); Thu, 30 Sep 2021 11:05:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:48532 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230370AbhI3PFr (ORCPT ); Thu, 30 Sep 2021 11:05:47 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8E2B560F4A; Thu, 30 Sep 2021 15:04:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1633014244; bh=nSTw+j4d2UCCKhsHid2M5WQ7GT4HxeOWxUwBItejV+c=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=g11GVhubWbJ/GMBOb23KR6WPBnQbnsPapEPAmH9W/CkHL4SrnZ6OSbtFjLvlWWwVA KI45hsV88rEDkrA4e9dQNzQPI63wb3PgbcgguUcOz9DEqcl+JUDxREpl7zAHJf05r4 EgArSxHg4bp6ARdwVMjfAU6NZ2jMy6WYnnx3r3UcgKD1bvzo36HdVJ+yDjeaeqc6Xs Of2ntw2JDzgpJnzTlcyjEX4Sdl5Yx10fgBVug4nheliVVzuitooDJs+nRHUdDo95Zx tndStmMdbBgumBc6UaOmEvZTg+43p8gVuuMe9Td4PFvkjWILpJQIRZsJJ2a/8RI5sW 3SmGakWn783xw== Date: Thu, 30 Sep 2021 10:04:02 -0500 From: Bjorn Helgaas To: Heikki Krogerus Cc: Greg Kroah-Hartman , "Rafael J. Wysocki" , Bjorn Helgaas , Andy Shevchenko , Zhangfei Gao , linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org Subject: Re: [PATCH v2 1/2] PCI: Convert to device_create_managed_software_node() Message-ID: <20210930150402.GA877907@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210930121246.22833-2-heikki.krogerus@linux.intel.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Sep 30, 2021 at 03:12:45PM +0300, Heikki Krogerus wrote: > In quirk_huawei_pcie_sva(), use device_create_managed_software_node() > instead of device_add_properties() to set the "dma-can-stall" > property. > > Reviewed-by: Andy Shevchenko > Acked-by: Zhangfei Gao > Signed-off-by: Heikki Krogerus > --- > Hi, > > The commit message now says what Bjorn requested, except I left out > the claim that the patch fixes a lifetime issue. Thanks. The commit log should help reviewers determine whether the change is safe and necessary. So far it doesn't have any hints along that line. Comparing device_add_properties() [1] and device_create_managed_software_node() [2], the only difference in this case is that the latter sets "swnode->managed = true". The function comment says "managed" means the lifetime of the swnode is tied to the lifetime of dev, hence my question about a lifetime issue. I can see that one reason for this change is to remove the last caller of device_add_properties(), so device_add_properties() itself can be removed. That's a good reason for wanting to do it, and the commit log could mention it. But it doesn't help me figure out whether it's safe. For that, I need to know the effect of setting "managed = true". Obviously it means *something*, but I don't know what. It looks like the only test is in software_node_notify(): device_del device_platform_notify_remove software_node_notify_remove sysfs_remove_link(dev_name) sysfs_remove_link("software_node") if (swnode->managed) <-- set_secondary_fwnode(dev, NULL) kobject_put(&swnode->kobj) device_remove_properties if (is_software_node()) fwnode_remove_software_node kobject_put(&swnode->kobj) set_secondary_fwnode(dev, NULL) I'm not sure what's going on here; it looks like some redundancy with multiple calls of kobject_put() and set_secondary_fwnode(). Maybe you are in the process of removing device_remove_properties() as well as device_add_properties()? [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/property.c?id=v5.14#n533 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/base/swnode.c?id=v5.14#n1083 > There shouldn't be any functional impact. > > thanks, > --- > drivers/pci/quirks.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c > index b6b4c803bdc94..fe5eedba47908 100644 > --- a/drivers/pci/quirks.c > +++ b/drivers/pci/quirks.c > @@ -1850,7 +1850,7 @@ static void quirk_huawei_pcie_sva(struct pci_dev *pdev) > * can set it directly. > */ > if (!pdev->dev.of_node && > - device_add_properties(&pdev->dev, properties)) > + device_create_managed_software_node(&pdev->dev, properties, NULL)) > pci_warn(pdev, "could not add stall property"); > } > DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_HUAWEI, 0xa250, quirk_huawei_pcie_sva); > -- > 2.33.0 >