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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 11 Mar 2013 17:09:55 +0100
Subject: [PATCH 216/342] x86/highmem: Add a "already used pte" check
Origin: https://git.kernel.org/cgit/linux/kernel/git/rt/linux-stable-rt.git/commit?id=7f6be1300407789b3a66f5ca8fa2bceef903b897
This is a copy from kmap_atomic_prot().
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/x86/mm/iomap_32.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/arch/x86/mm/iomap_32.c b/arch/x86/mm/iomap_32.c
index d5a48210d0f6..c0ec8d430c02 100644
--- 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 pfn, pgprot_t prot)
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
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