Re: [PATCH v2 08/16] PCI: Stop and remove devices in one pass

[Bjorn Helgaas <bhelgaas@google.com>]

On Fri, Aug 17, 2012 at 7:21 PM, Yinghai Lu <yinghai@kernel.org> wrote:
> On Fri, Aug 17, 2012 at 4:36 PM, Bjorn Helgaas <bhelgaas@google.com> wrote:
>> Previously, when we removed a PCI device, we made two passes over the
>> hierarchy rooted at the device.  In the first pass, we stopped all
>> the devices, and in the second, we removed them.
>>
>> This patch combines the two passes into one so that we remove a device as
>> soon as it and all its children have been stopped.
>>
>> Note that we previously stopped devices in reverse order and removed them
>> in forward order.  Now we stop and remove them in reverse order.
>>
>> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>> ---
>>  drivers/pci/remove.c |   42 +++++++-----------------------------------
>>  1 files changed, 7 insertions(+), 35 deletions(-)
>
> looks like your cleanup will have some conflict with my pci root bus
> hot plug branch.

Yes, indeed, they have serious conflicts.

> http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=blob;f=drivers/pci/remove.c;h=f672731922f8db619fb36db05dbd9c27f3253c19;hb=refs/heads/for-pci-root-bus-hotplug
>
> it add pci_stop_and_remove_bus and it depends on some functions that
> you kill in this patch set.

Do you have any suggestions on how to proceed?  In my opinion,
remove.c is a bit of a rat's nest right now.  It took me quite a long
time to sort out what's going on, but when you finally get down to the
bottom, it's actually very simple.  So I'd really like to clean it up
and expose that simple structure before we throw more stuff into it.

After my cleanup, pci_stop_and_remove_bus_device() and
pci_remove_bus() are the only exported interfaces left.  How hard
would it be to implement host bridge remove on top of that?

I think it's OK (and even preferable) if the host bridge-related code
can be segregated by itself rather than being sprinkled around through
lots of PCI code.  So maybe the pci_is_root_bus()  and
pci_stop_host_bridge() stuff below could be in some sort of host
bridge interface that just calls the code in remove.c.

>  180 void pci_stop_and_remove_bus(struct pci_bus *bus)
> 181 {
> 182         struct pci_host_bridge *host_bridge = NULL;
> 183         struct pci_dev *pci_bridge = NULL;
> 184
> 185         pci_stop_bus_devices(bus);
> 186
> 187         if (pci_is_root_bus(bus)) {
> 188                 host_bridge = to_pci_host_bridge(bus->bridge);
> 189                 get_device(&host_bridge->dev);
> 190                 pci_stop_host_bridge(host_bridge);
> 191         } else
> 192                 pci_bridge = bus->self;
> 193
> 194         __pci_remove_bus_devices(bus);
> 195
> 196         pci_remove_bus(bus);
> 197
> 198         if (host_bridge) {
> 199                 host_bridge->bus = NULL;
> 200                 put_device(&host_bridge->dev);
> 201         }
> 202
> 203         if (pci_bridge)
> 204                 pci_bridge->subordinate = NULL;
> 205 }
>
> Yinghai