Hi, please add udev rules to enable hotplugged CPUs and memory. I propose following two rules: ACTION=="add", SUBSYSTEM=="cpu", ATTR{online}=="0", ATTR{online}="1" ACTION=="add", SUBSYSTEM=="memory", ATTR{state}=="offline", ATTR{state}="online" These rules are tested (without the ATTR online/state checks) on Debian 7/testing, Fedora 19/20/21, and Ubuntu 12.04/13.10/14.04. Some distributions already ship CPU and memory hotplug rules. openSUSE 13.1 has 80-hotplug-cpu-mem.rules: SUBSYSTEM=="cpu", ACTION=="add", TEST=="online", ATTR{online}=="0", ATTR{online}="1" SUBSYSTEM=="memory", ACTION=="add", TEST=="state", ATTR{state}=="offline", ATTR{state}="online" CentOS 6 modified the acpi_memhotplug kernel module to automatically online memory (configurable with CONFIG_ACPI_HOTPLUG_MEMORY_AUTO_ONLINE). This patch is not mainlined (yet). They ship one rule for CPU hotplugging in /lib/udev/rules.d/40-redhat.rules: ACTION=="add", KERNEL=="cpu[0-9]*", RUN+="/bin/bash -c 'echo 1 > /sys/devices/system/cpu/%k/online'"
This is just a job for the kernel, it makes no sense to loop the kernel's events through userspace/udev, just to push the same information _unconditonally_ back into to the kernel. This needs to be sorted out in the kernel and not in userspace. At a general level, it is the very wrong model to do things, udev is not meant to do things like that. Even when some distributions ship this weird stuff, it does not make this right, and it cannot be the reason to copy this to upstream udev.
Use of freedesktop.org services, including Bugzilla, is subject to our Code of Conduct. How we collect and use information is described in our Privacy Policy.