With this patch applied my system survives me doing several rounds of: # echo 0 | tee /sys/devices/system/cpu/cpu*/online # echo 1 | tee /sys/devices/system/cpu/cpu*/online
whereas without the patch the first of those went to [152455.129604] NMI watchdog: Watchdog detected hard LOCKUP on cpu 96 [152455.136943] Kernel panic - not syncing: Hard LOCKUP I'm not sure we care to optimize the cpu offline path, but I'll note here that taking all (but one) cpus offline took 52 seconds (for a hundred and mumble logical cpus). Bringing them all back is just 4 seconds. Tested-by: Tony Luck <[email protected]>
