On Thu, Oct 27, 2011 at 12:08 AM, Michael Holzheu <holzheu at linux.vnet.ibm.com> wrote: > Hello Vivek and Eric, > Hello, > I noticed that on my system kernel 3.1 *no* udev events for memory > hotplug are generated. Same on my RHEL6.1. > > # udevadm monitor > # echo offline > /sys/devices/system/memory/memory4/state > > -> No event > > But we need the udev events in order to do a kdump reload for setting up > the ELF loads correctly. > > In my /etc/udev/rules.d/98-kexec.rules there are rules for memory > hotplug: > > SUBSYSTEM=="memory", ACTION=="add", PROGRAM="/etc/init.d/kdump restart" > SUBSYSTEM=="memory", ACTION=="remove", PROGRAM="/etc/init.d/kdump > restart" > > Perhaps/probably I am missing something? As Heiko pointed out, probably the memory-hotplug subsystem doesn't implement uevent, this is why you can't get uevent when you hot-remove the memory. For kdump, the memory is reserved by "crashkernel=", it is determined during boot (but you can shrink it after boot), so it is not aware of memory hotplug. IOW, if you hot-remove the memory where the crash kernel stays, the 'kdump restart' will fail. But yes, restarting kdump can rebuild the memmap and ELF headers. Thanks.
