Bug: linux/acpi may execute notify handler that has been removed

[Zhang Rui <rui.zhang@intel.com>]

Hi, all,

I found a bug that linux/acpi may execute notify handler that
has been removed.

When a system notify(0~0x7f) is received, linux/acpi will
first invoke the generic system notify handler (acpi_bus_notify)
and then invoke the per-device notify handler if present.

In my case, I add some code in acpi_bus_notify for battery
hotplug support, so that the generic system notify handler will
remove the battery device, including the per-device notify handler
acpi_battery_notify() when receiving notification
ACPI_NOTIFY_EJECT_REQUEST.
But linux/acpi invokes the per-device notify handler soon and
this breaks the system.

Further more, device hot-removal is not the only case to encounter
this bug. For example, linux/acpi receives a notification and adds it
in the workqueue, and then the driver(notify handler) is removed
before kacpid_notify invoke it...

Attachment is the patch for battery hotplug support.
Any ideas about this bug?

Thanks,
Rui