On Fri, 2012-11-16 at 15:33 -0800, Greg Kroah-Hartman wrote: > On Fri, Nov 16, 2012 at 04:14:44PM -0700, Toshi Kani wrote: > > On Fri, 2012-11-16 at 15:01 -0800, Greg Kroah-Hartman wrote: > > > On Fri, Nov 16, 2012 at 03:45:43PM -0700, Toshi Kani wrote: > > > > On Fri, 2012-11-16 at 22:43 +0100, Rafael J. Wysocki wrote: > > > > > On Thursday, November 15, 2012 11:22:47 AM Vasilis Liaskovitis wrote: > > > > > > As discussed in https://patchwork.kernel.org/patch/1581581/ > > > > > > the driver core remove function needs to always succeed. This means we need > > > > > > to know that the device can be successfully removed before acpi_bus_trim / > > > > > > acpi_bus_hot_remove_device are called. This can cause panics when OSPM-initiated > > > > > > eject or driver unbind of memory devices fails e.g with: > > > > > > > > > > > > echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject > > > > > > echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind > > > > > > > > > > > > since the ACPI core goes ahead and ejects the device regardless of whether the > > > > > > the memory is still in use or not. > > > > > > > > > > So the question is, does the ACPI core have to do that and if so, then why? > > > > > > > > The problem is that acpi_memory_devcie_remove() can fail. However, > > > > device_release_driver() is a void function, so it cannot report its > > > > error. Here are function flows for SCI, sysfs eject and unbind. > > > > > > Then don't ever let acpi_memory_device_remove() fail. If the user wants > > > it gone, it needs to go away. Just like any other device in the system > > > that can go away at any point in time, you can't "fail" that. > > > > That would be ideal, but we cannot delete a memory device that contains > > kernel memory. I am curious, how do you deal with a USB device that is > > being mounted in this case? > > As the device is physically gone now, we deal with it and clean up > properly. > > And that's the point here, what happens if the memory really is gone? > You will still have to handle it now being removed, you can't "fail" a > physical removal of a device. > > If you remove a memory device that has kernel memory on it, well, you > better be able to somehow remap it before the kernel needs it :) :) Well, we are not trying to support surprise removal here. All three use-cases (SCI, eject, and unbind) are for graceful removal. Therefore they should fail if the removal operation cannot complete in graceful way. Thanks, -Toshi -- 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>