The errors popped up in -RT. One is the spinlock_t usage in IRQ-off region which should be a raw_spinlock_t. I don't see this to be used during run-time or for long period of time so I don't thing this is an issue.
The second problem is the ->pend_page allocation on the target_cpu early during CPU bring up. It would be simpler to allocate the memory once on the boot CPU instead the hotplug callback since the memory is never free()ed. I *think* this is avoided because the number of possible CPUs might be higher than what will actually come up (on x86 the BIOS sometimes reports more possible_cpus than what is *really* possible, not sure if ARM64 is there yet). Therefore I moved the allocation to an earlier callback. Sebastian
