On Wednesday, November 28, 2012 03:16:22 PM Toshi Kani wrote: > > > > > > > I see. I do not think whether or not the device is removed on eject > > > > > > > makes any difference here. The issue is that after driver_unbind() is > > > > > > > done, acpi_bus_hot_remove_device() no longer calls the ACPI memory > > > > > > > driver (hence, it cannot fail in prepare_remove), and goes ahead to call > > > > > > > _EJ0. If driver_unbind() did off-line the memory, this is OK. However, > > > > > > > it cannot off-line kernel memory ranges. So, we basically need to > > > > > > > either 1) serialize acpi_bus_hot_remove_device() and driver_unbind(), or > > > > > > > 2) make acpi_bus_hot_remove_device() to fail if driver_unbind() is run > > > > > > > during the operation. > > > > > > > > > > > > OK, I see the problem now. > > > > > > > > > > > > What exactly is triggering the driver_unbind() in this scenario? > > > > > > > > > > User can request driver_unbind() from sysfs as follows. I do not see > > > > > much reason why user has to do for memory, though. > > > > > > > > > > echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind > > > > > > > > This is wrong. Even if we want to permit user space to forcibly unbind > > > > drivers from anything like this, we should at least check for some > > > > situations in which it is plain dangerous. Like in this case. So I think > > > > the above should fail unless we know that the driver won't be necessary > > > > to handle hot-removal of memory. > > > > > > Well, we tried twice already... :) > > > https://lkml.org/lkml/2012/11/16/649 > > > > I didn't mean driver_unbind() should fail. The code path that executes > > driver_unbind() eventually should fail _before_ executing it. > > driver_unbind() is the handler, so it is called directly from this > unbind interface. Yes, sorry for the confusion. So, it looks like the driver core wants us to handle driver unbinding no matter what. This pretty much means that it is a bad idea to have a driver that is exposed as a "device driver" in sysfs for memory hotplugging. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>