From: Sebastian Andrzej Siewior Date: Mon, 11 Mar 2013 17:09:55 +0100 Subject: x86/highmem: Add a "already used pte" check Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.19/older/patches-4.19.25-rt16.tar.xz This is a copy from kmap_atomic_prot(). Signed-off-by: Sebastian Andrzej Siewior --- arch/x86/mm/iomap_32.c | 2 ++ 1 file changed, 2 insertions(+) --- a/arch/x86/mm/iomap_32.c +++ b/arch/x86/mm/iomap_32.c @@ -69,6 +69,8 @@ void *kmap_atomic_prot_pfn(unsigned long type = kmap_atomic_idx_push(); idx = type + KM_TYPE_NR * smp_processor_id(); vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx); + WARN_ON(!pte_none(*(kmap_pte - idx))); + #ifdef CONFIG_PREEMPT_RT_FULL current->kmap_pte[type] = pte; #endif