At 11/26/2012 04:36 PM, Vasilis Liaskovitis Wrote: > On Sun, Nov 25, 2012 at 12:20:47AM +0800, Wen Congyang wrote: >> At 2012/11/24 1:50, Vasilis Liaskovitis Wrote: >>> Consider the following sequence of operations for a hotplugged memory device: >>> >>> 1. echo "PNP0C80:XX"> /sys/bus/acpi/drivers/acpi_memhotplug/unbind >>> 2. echo "PNP0C80:XX"> /sys/bus/acpi/drivers/acpi_memhotplug/bind >>> 3. echo 1>/sys/bus/pci/devices/PNP0C80:XX/eject >>> >>> The driver is successfully re-bound to the device in step 2. However step 3 will >>> not attempt to remove the memory. This is because the acpi_memory_info enabled >>> bit for the newly bound driver has not been set to 1. This bit needs to be set >>> in the case where the memory is already used by the kernel (add_memory returns >>> -EEXIST) >> >> Hmm, I think the reason is that we don't offline/remove memory when >> unbinding it >> from the driver. I have sent a patch to fix this problem, and this patch >> is in >> pm tree now. With this patch, we will offline/remove memory when >> unbinding it from >> the drriver. > > ok. Which patch is this? Does it require driver-core changes? https://lkml.org/lkml/2012/11/15/21 Patch 1-6 is in pm tree now. > >> >> Consider the following sequence of operations for a hotplugged memory >> device: >> >> 1. echo "PNP0C80:XX" > /sys/bus/acpi/drivers/acpi_memhotplug/unbind >> 2. echo 1 >/sys/bus/pci/devices/PNP0C80:XX/eject >> >> If we don't offline/remove the memory, we have no chance to do it in >> step 2. After >> step2, the memory is used by the kernel, but we have powered off it. It >> is very >> dangerous. > > How does power-off happen after unbind? acpi_eject_store checks for existing > driver before taking any action: > > #ifndef FORCE_EJECT > if (acpi_device->driver == NULL) { > ret = -ENODEV; > goto err; > } > #endif > > FORCE_EJECT is not defined afaict, so the function returns without scheduling > acpi_bus_hot_remove_device. Is there another code path that calls power-off? Consider the following case: We hotremove the memory device by SCI and unbind it from the driver at the same time: CPUa CPUb acpi_memory_device_notify() unbind it from the driver acpi_bus_hot_remove_device() Thanks Wen Congyang > > thanks, > > - Vasilis > -- 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>