Re: [PATCH] pci: Add support for unbinding the generic PCI host controller

From: Will Deacon
Date: Fri Jun 24 2016 - 02:12:41 EST


On Thu, Jun 23, 2016 at 07:31:34PM +0200, Jan Kiszka wrote:
> On 2016-06-22 08:06, Will Deacon wrote:
> > On Tue, Jun 21, 2016 at 08:07:50PM +0200, Jan Kiszka wrote:
> >> diff --git a/drivers/pci/host/pci-host-common.c b/drivers/pci/host/pci-host-common.c
> >> index 8cba7ab..c0ff4b1 100644
> >> --- a/drivers/pci/host/pci-host-common.c
> >> +++ b/drivers/pci/host/pci-host-common.c
> >> @@ -164,6 +164,19 @@ int pci_host_common_probe(struct platform_device *pdev,
> >> }
> >>
> >> pci_bus_add_devices(bus);
> >> + platform_set_drvdata(pdev, bus);
> >> + return 0;
> >> +}
> >> +
> >> +int pci_host_common_remove(struct platform_device *pdev)
> >> +{
> >> + struct pci_bus *bus = platform_get_drvdata(pdev);
> >> +
> >> + pci_lock_rescan_remove();
> >> + pci_stop_root_bus(bus);
> >> + pci_remove_root_bus(bus);
> >> + pci_unlock_rescan_remove();
> >
> > A couple of comments/questions about this:
> >
> > - The probe path seems to have some stateful operations outside of PCI
> > resources. For example, kzalloc'ing the bus_range resource in
> > of_pci_get_host_bridge_resources. Do we need to clean these up
> > explicitly?
> >
> > - Similarly, we don't seem to tear-down the config space mappings and
> > data structures for that, so we leak VA space afaict.
> >
>
> Good points. But to my understanding, everything is released
> automatically on pci_remove_root_bus because all the resources are
> registered with the bus which takes care of them during destruction. And
> if I trace the release, I find this e.g.
>
> ...
> devres_release_all() {
> _raw_spin_lock_irqsave();
> release_nodes() {
> _raw_spin_unlock_irqrestore();
> devm_action_release() {
> gen_pci_unmap_cfg() {

Ah, thanks for investigating that -- I completely missed the explicit
devm_ callback. That resolves my concern about the config space mappings,
but I still don't understand what happens to the resources allocated
in of_pci_get_host_bridge_resources. It looks like they should actually
be freed within that function, since pci_add_resource{_offset} copy the
resources into their own resource_entries anyway.

Am I missing something?

Will