linux-kernel - Re: [PATCH linux-next] PCI: Fix the order in unregister path

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Date:   Wed, 25 Aug 2021 08:55:24 -0500
From:   Rob Herring <robh@...nel.org>
To:     Yajun Deng <yajun.deng@...ux.dev>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>, Arnd Bergmann <arnd@...db.de>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        PCI <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH linux-next] PCI: Fix the order in unregister path

On Wed, Aug 25, 2021 at 3:34 AM Yajun Deng <yajun.deng@...ux.dev> wrote:
>
> device_del() should be called first and then called put_device() in
> unregister path, becase if that the final reference count, the device
> will be cleaned up via device_release() above. So use device_unregister()
> instead.
>
> Fixes: 9885440b16b8 (PCI: Fix pci_host_bridge struct device release/free handling)
> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
> ---
>  drivers/pci/probe.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)

NAK.

The current code is correct. Go read the comments for device_add/device_del.

> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 0ec5c792c27d..abd481a15a17 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -994,9 +994,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
>         return 0;
>
>  unregister:

We get here if device_register() failed. Calling device_unregister()
in that case is never right.

> -       put_device(&bridge->dev);

This is for the get_device() we do above, not the get the driver core does.

> -       device_del(&bridge->dev);

This undoes the device_add() we do following the comment: "NOTE: this
should be called manually _iff_ device_add() was also called
manually."

> -
> +       device_unregister(&bridge->dev);
>  free:
>         kfree(bus);
>         return err;
> --
> 2.32.0
>