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. SCI & sysfs eject === acpi_bus_hot_remove_device() acpi_bus_trim() acpi_bus_remove() device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver acpi_evaluate_object(handle, "_EJ0",,) // Eject sysfs unbind === driver_unbind() // Driver Core device_release_driver() // Driver Core acpi_device_remove() acpi_memory_device_remove() // ACPI Driver put_device() bus_put() Yasuaki's approach was to change device_release_driver() to report an error so that acpi_bus_hot_remove_device() can fail without ejecting. Vasilis's approach was to call ACPI driver via a new interface before device_release_driver(), but still requires to change driver_unbind(). It looks to me that some changes to driver core is needed... 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>