From 93cd8a21dbc8ab841eea0e4dbe2c6d7dde6bc2b6 Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 30 Oct 2020 13:59:06 +0100
Subject: [PATCH 062/327] highmem: Don't disable preemption on RT in
 kmap_atomic()

Disabling preemption makes it impossible to acquire sleeping locks within
kmap_atomic() section.
For PREEMPT_RT it is sufficient to disable migration.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 include/linux/highmem-internal.h | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index bd15bf9164c2..f9bc6acd3679 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -90,7 +90,10 @@ static inline void __kunmap_local(void *vaddr)
 
 static inline void *kmap_atomic(struct page *page)
 {
-	preempt_disable();
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		migrate_disable();
+	else
+		preempt_disable();
 	pagefault_disable();
 	return __kmap_local_page_prot(page, kmap_prot);
 }
@@ -99,7 +102,10 @@ static inline void __kunmap_atomic(void *addr)
 {
 	kunmap_local_indexed(addr);
 	pagefault_enable();
-	preempt_enable();
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		migrate_enable();
+	else
+		preempt_enable();
 }
 
 unsigned int __nr_free_highpages(void);
@@ -172,7 +178,10 @@ static inline void __kunmap_local(void *addr)
 
 static inline void *kmap_atomic(struct page *page)
 {
-	preempt_disable();
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		migrate_disable();
+	else
+		preempt_disable();
 	pagefault_disable();
 	return page_address(page);
 }
@@ -183,7 +192,10 @@ static inline void __kunmap_atomic(void *addr)
 	kunmap_flush_on_unmap(addr);
 #endif
 	pagefault_enable();
-	preempt_enable();
+	if (IS_ENABLED(CONFIG_PREEMPT_RT))
+		migrate_enable();
+	else
+		preempt_enable();
 }
 
 static inline unsigned int nr_free_highpages(void) { return 0; }
-- 
2.49.0

