linux-kernel - Re: [PATCH v2 1/1] Guard pci_create_sysfs_dev

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Date:   Thu, 16 Mar 2023 12:17:32 +0100
From:   Oliver Neukum <oneukum@...e.com>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Oliver Neukum <oneukum@...e.com>
Cc:     Korneliusz Osmenda <korneliuszo@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] Guard pci_create_sysfs_dev_files with atomic value

On 16.03.23 10:33, Alexander Stein wrote:
> Hi Oliver,

Hi,

> 
> Admittedly
> I would like to get rid of these two pathes for creating sysfs files in the
> first place, but I do not know the pci subsystem very well.
> IMHO for_each_pci_dev(pdev) in pci_sysfs_init is part of the problem as it
> unconditionally iterates over the bus, without any locks, thus creating sysfs
> files for each device added to the bus.
> Any ideas?

First of all, this existing code is a mess.

If I understand you have the issue that your driver adds a bridge
in dw_pcie_host_init() and the generic code in pci_create_sysfs_dev_files()
populates the directory before or while your driver does so and
the devices are effectively discovered twice.

It seems to me that you must not add a bridge before pci_create_sysfs_dev_files()
has finished. Now you could add a wait_queue and a flag and wait for it to
finish. But that is not very elegant. From which initcall is your driver
probed?

	Regards
		Oliver