Skip to content
Browse files

Driver core: treat unregistered bus_types as having no devices

commit 4fa3e78 upstream.

A bus_type has a list of devices (klist_devices), but the list and the
subsys_private structure that contains it are not initialized until the
bus_type is registered with bus_register().

The panic/reboot path has fixups that look up devices in pci_bus_type.  If
we panic before registering pci_bus_type, the bus_type exists but the list
does not, so mach_reboot_fixups() trips over a null pointer and panics

          bus_find_device(&pci_bus_type, ...)
            bus->p is NULL

Joonsoo reported a problem when panicking before PCI was initialized.
I think this patch should be sufficient to replace the patch he posted
here: ("[PATCH] x86, reboot: skip
reboot_fixups in early boot phase")

Reported-by: Joonsoo Kim <>
Signed-off-by: Bjorn Helgaas <>
Signed-off-by: Greg Kroah-Hartman <>
  • Loading branch information...
1 parent 2199a65 commit 362efcc9b0ba020f9124c70c56381ed64491aeca @bjorn-helgaas bjorn-helgaas committed with gregkh Jan 29, 2013
Showing with 2 additions and 2 deletions.
  1. +2 −2 drivers/base/bus.c
4 drivers/base/bus.c
@@ -294,7 +294,7 @@ int bus_for_each_dev(struct bus_type *bus, struct device *start,
struct device *dev;
int error = 0;
- if (!bus)
+ if (!bus || !bus->p)
return -EINVAL;
klist_iter_init_node(&bus->p->klist_devices, &i,
@@ -328,7 +328,7 @@ struct device *bus_find_device(struct bus_type *bus,
struct klist_iter i;
struct device *dev;
- if (!bus)
+ if (!bus || !bus->p)
return NULL;
klist_iter_init_node(&bus->p->klist_devices, &i,

0 comments on commit 362efcc

Please sign in to comment.
Something went wrong with that request. Please try again.