Re: [PATCH v1 00/25] PCI: Request host bridge window resources

Bjorn Helgaas
2016-06-21T15:03:52Z

On Tue, Jun 21, 2016 at 07:58:08PM +0800, wangyijing wrote:
> Hi Bjorn, use devm_request_resource() for host bridge resource is cool,
> what about do the similar change for x86, now we request host bridge resource
> in pci_acpi_root_add_resources() in x86, and we would release the host bridge
> resource when host bridge device refcount reach 0. This logic may introduce issue,
> E.g.
> If we try to remove a pci host bridge, but there is a child pci device which refcount
> cannot decrease to 0 after remove the device, in this case, its parent pci_bus and
> parent device, all their refcount cannot reach to 0, the result is pci host bridge
> refcount can not reach 0, so its .release_fn() won't be called, and host bridge
> resouces can not release. If we want to add the pci host bridge again, all pci devices
> can not work because the resource is conflict with the old.
>
> devm resource would be released when the driver detach, this is better than what we do now, I think.

I'm not going to convert pci_root.c to use devm right now. That might
be a good thing, but this current series is mostly trivial. I think
changing pci_root.c would not be trivial, so that looks like a project
all by itself.

I don't quite follow the example of removing a host bridge while a
child PCI device refcount is non-zero. That sounds like an invalid
scenario regardless of whether the resources are released by a
.release_fn() or by devm.

Bjorn