linux-kernel - Re: [PATCH v8 06/22] PCI: split registration of PCI bus devices into two stages

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Date:	Sun, 13 Jan 2013 23:25:46 +0800
From:	Jiang Liu <liuj97@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Len Brown <lenb@...nel.org>,
	Taku Izumi <izumi.taku@...fujitsu.com>,
	Jiang Liu <jiang.liu@...wei.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v8 06/22] PCI: split registration of PCI bus devices into
 two stages

On 01/13/2013 06:34 AM, Rafael J. Wysocki wrote:
> On Friday, January 11, 2013 02:40:33 PM Yinghai Lu wrote:
>> From: Jiang Liu <jiang.liu@...wei.com>
>>
>> When handling BUS_NOTIFY_ADD_DEVICE event for a PCI bridge device,
>> the notification handler can't hold reference count to the new PCI bus
>> because the device object for the new bus (pci_dev->subordinate->dev)
>> hasn't been initialized yet.
> 
> It doesn't look like BUS_NOTIFY_ADD_DEVICE is used by the PCI bus type
> in the mainline.
> 
> Is it in linux-next?
> 
> If not, then I don't see why we need this patch.
Hi Rafael,
	Originally it's a preparation patch for pci_slot/acpiphp/pci_bind
related fixups. With recent work from you to remove bind/unbind from struct
acpi_bus_type, we have no dependency on this patch anymore.
Regards!
Gerry

> 
> Thanks,
> Rafael
> 
> 
>> Split the registration of PCI bus device into two stages as below,
>> so that the event handler could hold reference count to the new PCI bus
>> when handling BUS_NOTIFY_ADD_DEVICE event.
>>
>> 1) device_initialize(&pci_dev->dev)
>> 2) device_initialize(&pci_dev->subordinate->dev)
>> 3) notify BUS_NOTIFY_ADD_DEVICE event for pci_dev
>> 4) device_add(&pci_dev->dev)
>> 5) device_add(&pci_dev->subordinate->dev)
>>
>> Signed-off-by: Jiang Liu <jiang.liu@...wei.com>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> ---
>>  drivers/pci/bus.c    |    2 +-
>>  drivers/pci/probe.c  |    4 +++-
>>  drivers/pci/remove.c |   10 +++++-----
>>  3 files changed, 9 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
>> index 847f3ca..5f9c728 100644
>> --- a/drivers/pci/bus.c
>> +++ b/drivers/pci/bus.c
>> @@ -200,7 +200,7 @@ int pci_bus_add_child(struct pci_bus *bus)
>>  	if (bus->bridge)
>>  		bus->dev.parent = bus->bridge;
>>  
>> -	retval = device_register(&bus->dev);
>> +	retval = device_add(&bus->dev);
>>  	if (retval)
>>  		return retval;
>>  
>> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
>> index 48b35e1..dc4fde3 100644
>> --- a/drivers/pci/probe.c
>> +++ b/drivers/pci/probe.c
>> @@ -642,6 +642,7 @@ static struct pci_bus *pci_alloc_child_bus(struct pci_bus *parent,
>>  	 */
>>  	child->dev.class = &pcibus_class;
>>  	dev_set_name(&child->dev, "%04x:%02x", pci_domain_nr(child), busnr);
>> +	device_initialize(&child->dev);
>>  
>>  	/*
>>  	 * Set up the primary, secondary and subordinate
>> @@ -1678,7 +1679,8 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>>  	b->dev.class = &pcibus_class;
>>  	b->dev.parent = b->bridge;
>>  	dev_set_name(&b->dev, "%04x:%02x", pci_domain_nr(b), bus);
>> -	error = device_register(&b->dev);
>> +	device_initialize(&b->dev);
>> +	error = device_add(&b->dev);
>>  	if (error)
>>  		goto class_dev_reg_err;
>>  
>> diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c
>> index fc38c48..a1fdd0f 100644
>> --- a/drivers/pci/remove.c
>> +++ b/drivers/pci/remove.c
>> @@ -48,11 +48,11 @@ void pci_remove_bus(struct pci_bus *bus)
>>  	list_del(&bus->node);
>>  	pci_bus_release_busn_res(bus);
>>  	up_write(&pci_bus_sem);
>> -	if (!bus->is_added)
>> -		return;
>> -
>> -	pci_remove_legacy_files(bus);
>> -	device_unregister(&bus->dev);
>> +	if (bus->is_added) {
>> +		pci_remove_legacy_files(bus);
>> +		device_del(&bus->dev);
>> +	}
>> +	put_device(&bus->dev);
>>  }
>>  EXPORT_SYMBOL(pci_remove_bus);
>>  
>>

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