On Thu, May 02, 2013 at 02:27:30PM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > In some cases, graceful hot-removal of devices is not possible, > although in principle the devices in question support hotplug. > For example, that may happen for the last CPU in the system or > for memory modules holding kernel memory. > > In those cases it is nice to be able to check if the given device > can be gracefully hot-removed before triggering a removal procedure > that cannot be aborted or reversed. Unfortunately, however, the > kernel currently doesn't provide any support for that. > > To address that deficiency, introduce support for offline and > online operations that can be performed on devices, respectively, > before a hot-removal and in case when it is necessary (or convenient) > to put a device back online after a successful offline (that has not > been followed by removal). The idea is that the offline will fail > whenever the given device cannot be gracefully removed from the > system and it will not be allowed to use the device after a > successful offline (until a subsequent online) in analogy with the > existing CPU offline/online mechanism. > > For now, the offline and online operations are introduced at the > bus type level, as that should be sufficient for the most urgent use > cases (CPUs and memory modules). In the future, however, the > approach may be extended to cover some more complicated device > offline/online scenarios involving device drivers etc. > > The lock_device_hotplug() and unlock_device_hotplug() functions are > introduced because subsequent patches need to put larger pieces of > code under device_hotplug_lock to prevent race conditions between > device offline and removal from happening. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
