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Driver core: treat unregistered bus_types as having no devices 

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
again:

    mach_reboot_fixups
      pci_get_device
        ..
          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: https://lkml.org/lkml/2012/12/28/75 ("[PATCH] x86, reboot: skip
reboot_fixups in early boot phase")

Reported-by: Joonsoo Kim <js1304@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Bjorn Helgaas 2013-01-29 16:44:27 -07:00 committed by Greg Kroah-Hartman
parent 422d26b6ec
commit 4fa3e78be7
1 changed files with 2 additions and 2 deletions
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4
drivers/base/bus.c
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@ -290,7 +290,7 @@ 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,
@ -324,7 +324,7 @@ 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,