On Tue, Feb 12, 2013 at 4:19 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > This changeset is aimed at fixing a few different but related > problems in the ACPI hotplug infrastructure. > > First of all, since notify handlers may be run in parallel with > acpi_bus_scan(), acpi_bus_trim() and acpi_bus_hot_remove_device() > and some of them are installed for ACPI handles that have no struct > acpi_device objects attached (i.e. before those objects are created), > those notify handlers have to take acpi_scan_lock to prevent races > from taking place (e.g. a struct acpi_device is found to be present > for the given ACPI handle, but right after that it is removed by > acpi_bus_trim() running in parallel to the given notify handler). > Moreover, since some of them call acpi_bus_scan() and > acpi_bus_trim(), this leads to the conclusion that acpi_scan_lock > should be acquired by the callers of these two funtions rather by > these functions themselves. > > For these reasons, make all notify handlers that can handle device > addition and eject events take acpi_scan_lock and remove the > acpi_scan_lock locking from acpi_bus_scan() and acpi_bus_trim(). > Accordingly, update all of their users to make sure that they > are always called under acpi_scan_lock. > > Furthermore, since eject operations are carried out asynchronously > with respect to the notify events that trigger them, with the help > of acpi_bus_hot_remove_device(), even if notify handlers take the > ACPI scan lock, it still is possible that, for example, > acpi_bus_trim() will run between acpi_bus_hot_remove_device() and > the notify handler that scheduled its execution and that > acpi_bus_trim() will remove the device node passed to > acpi_bus_hot_remove_device() for ejection. In that case, the struct > acpi_device object obtained by acpi_bus_hot_remove_device() will be > invalid and not-so-funny things will ensue. To protect agaist that, > make the users of acpi_bus_hot_remove_device() run get_device() on > ACPI device node objects that are about to be passed to it and make > acpi_bus_hot_remove_device() run put_device() on them and check if > their ACPI handles are not NULL (make acpi_device_unregister() clear > the device nodes' ACPI handles for that check to work). > > Finally, observe that acpi_os_hotplug_execute() actually can fail, > in which case its caller ought to free memory allocated for the > context object to prevent leaks from happening. It also needs to > run put_device() on the device node that it ran get_device() on > previously in that case. Modify the code accordingly. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Acked-by: Yinghai Lu <yinghai@xxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
