Pull CPU hotplug fix from Thomas Gleixner:
"A single fix preventing the concurrent execution of the CPU hotplug
callback install/invocation machinery. Long standing bug caused by a
massive brain slip of that Gleixner dude, which went unnoticed for
almost a year"
* 'smp-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
cpu/hotplug: Serialize callback invocations proper