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

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Date:   Thu, 26 Aug 2021 03:57:40 +0000
From:   yajun.deng@...ux.dev
To:     "Rob Herring" <robh@...nel.org>
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
Subject: Re: [PATCH linux-next] PCI: Fix the order in unregister path

August 25, 2021 9:55 PM, "Rob Herring" <robh@...nel.org> wrote:

> 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.

But the device_unregister() is only contains device_del() and put_device(). It just put
device_del() before put_device().

> 
>> 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