Subject: arm: highmem: Use kmap for PREEMPT_RT
From: Thomas Gleixner <tglx@linutronix.de>
Date: Thu, 11 Oct 2012 22:59:24 +0200

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
 arch/arm/Kconfig               |    2 +-
 arch/arm/include/asm/highmem.h |   15 +++++++++++++++
 arch/arm/mm/highmem.c          |    2 ++
 3 files changed, 18 insertions(+), 1 deletion(-)

Index: linux-stable/arch/arm/Kconfig
===================================================================
--- linux-stable.orig/arch/arm/Kconfig
+++ linux-stable/arch/arm/Kconfig
@@ -1749,7 +1749,7 @@ config HAVE_ARCH_PFN_VALID
 
 config HIGHMEM
 	bool "High Memory Support"
-	depends on MMU && !PREEMPT_RT_FULL
+	depends on MMU
 	help
 	  The address space of ARM processors is only 4 Gigabytes large
 	  and it has to accommodate user address space, kernel address
Index: linux-stable/arch/arm/include/asm/highmem.h
===================================================================
--- linux-stable.orig/arch/arm/include/asm/highmem.h
+++ linux-stable/arch/arm/include/asm/highmem.h
@@ -57,10 +57,25 @@ static inline void *kmap_high_get(struct
 #ifdef CONFIG_HIGHMEM
 extern void *kmap(struct page *page);
 extern void kunmap(struct page *page);
+# ifndef CONFIG_PREEMPT_RT_FULL
 extern void *kmap_atomic(struct page *page);
 extern void __kunmap_atomic(void *kvaddr);
 extern void *kmap_atomic_pfn(unsigned long pfn);
 extern struct page *kmap_atomic_to_page(const void *ptr);
+# else
+#  define kmap_atomic(page)	\
+	({ pagefault_disable(); kmap(page); })
+
+#  define kmap_atomic_pfn(pfn)	\
+	({ pagefault_disable(); kmap(pfn_to_page(pfn)) })
+
+#  define __kunmap_atomic(kvaddr)	\
+	do { kunmap(kmap_to_page(kvaddr)); pagefault_enable(); } while(0)
+
+#  define kmap_atomic_to_page(kvaddr)	\
+	kmap_to_page(kvaddr)
+
+# endif
 #endif
 
 #endif
Index: linux-stable/arch/arm/mm/highmem.c
===================================================================
--- linux-stable.orig/arch/arm/mm/highmem.c
+++ linux-stable/arch/arm/mm/highmem.c
@@ -36,6 +36,7 @@ void kunmap(struct page *page)
 }
 EXPORT_SYMBOL(kunmap);
 
+#ifndef CONFIG_PREEMPT_RT_FULL
 void *kmap_atomic(struct page *page)
 {
 	unsigned int idx;
@@ -135,3 +136,4 @@ struct page *kmap_atomic_to_page(const v
 
 	return pte_page(get_top_pte(vaddr));
 }
+#endif