On Tuesday, February 12, 2013 05:55:26 PM Yinghai Lu wrote: > 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> Thanks! -- 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
