On Fri 12-12-25 16:18:32, Yeoreum Yun wrote:

linear_map_split_to_ptes() and __kpti_install_ng_mappings()
are called as callback of stop_machine().
That means these functions context are preemption disabled.

Unfortunately, under PREEMPT_RT, the pagetable_alloc() or
__get_free_pages() couldn't be called in this context
since spin lock that becomes sleepable on RT,
potentially causing a sleep during page allocation.

To address this, pagetable_alloc_nolock().

As you cannot tolerate allocation failure and this is pretty much
permanent allocation (AFAIU) why don't you use a static allocation?

-- 
Michal Hocko
SUSE Labs