On Fri, Sep 21, 2012 at 1:14 AM, Taku Izumi [off-list ref] wrote:

On Wed, 19 Sep 2012 16:03:27 -0600
Bjorn Helgaas [off-list ref] wrote:

quoted

On Tue, Sep 18, 2012 at 12:23 AM, Taku Izumi [off-list ref] wrote:

quoted

This patch changes the implementation of acpi_pci_find_root().

We can access acpi_pci_root without scanning acpi_pci_roots list.
If hostbridge hotplug is supported, acpi_pci_roots list will be
protected by mutex. We should not access acpi_pci_roots list
if preventable to lessen deadlock risk.

Signed-off-by: Taku Izumi <redacted>
---
 drivers/acpi/pci_root.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Index: Bjorn-next-0903/drivers/acpi/pci_root.c
===================================================================

--- Bjorn-next-0903.orig/drivers/acpi/pci_root.c
+++ Bjorn-next-0903/drivers/acpi/pci_root.c

@@ -265,12 +265,15 @@ static acpi_status acpi_pci_osc_support(
 struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
 {
        struct acpi_pci_root *root;
+       struct acpi_device *device;

-       list_for_each_entry(root, &acpi_pci_roots, node) {
-               if (root->device->handle == handle)
-                       return root;
-       }
-       return NULL;
+       if (acpi_bus_get_device(handle, &device) ||
+           acpi_match_device_ids(device, root_device_ids))

What's the purpose of the acpi_match_device_ids() check?  It's not
obvious, so worth calling it out in the changelog, and maybe even a
comment in the code.

  My intention is to reject acpi_handle which doesn't represent
  hostbrige. I think this is reasonable...

Yes, I understand that part.  I was just trying to figure out why that
check is needed.  Is there a path where we can call
acpi_pci_find_root() with a handle that is *not* a PNP0A03 device?  I
looked at all the callers, and as far as I can tell, the supplied
handle is always for a host bridge device.

But I guess I don't object to the check.  This is just another case of
a lookup that in many cases is unnecessary because we should have the
struct acpi_pci_root * available already.

quoted

Nice to get rid of the list traversal.

quoted

+               return NULL;
+
+       root = acpi_driver_data(device);
+
+       return root;
 }
 EXPORT_SYMBOL_GPL(acpi_pci_find_root);

--
Taku Izumi [off-list ref]