spinlocks and preemption points need to be at least compiler barriers

[linux-3.10.git] / include / linux / preempt.h

diff --git a/include/linux/preempt.h b/include/linux/preempt.h
index 5a710b9c578e2881478872d505e8b649e8bdb55f..87a03c746f177be0b4ddc0dee6a61860d596ff3d 100644 (file)
--- a/include/linux/preempt.h
+++ b/include/linux/preempt.h
@@ -93,14 +93,20 @@ do { \
 
 #else /* !CONFIG_PREEMPT_COUNT */
 
-#define preempt_disable()              do { } while (0)
-#define sched_preempt_enable_no_resched()      do { } while (0)
-#define preempt_enable_no_resched()    do { } while (0)
-#define preempt_enable()               do { } while (0)
-
-#define preempt_disable_notrace()              do { } while (0)
-#define preempt_enable_no_resched_notrace()    do { } while (0)
-#define preempt_enable_notrace()               do { } while (0)
+/*
+ * Even if we don't have any preemption, we need preempt disable/enable
+ * to be barriers, so that we don't have things like get_user/put_user
+ * that can cause faults and scheduling migrate into our preempt-protected
+ * region.
+ */
+#define preempt_disable()              barrier()
+#define sched_preempt_enable_no_resched()      barrier()
+#define preempt_enable_no_resched()    barrier()
+#define preempt_enable()               barrier()
+
+#define preempt_disable_notrace()              barrier()
+#define preempt_enable_no_resched_notrace()    barrier()
+#define preempt_enable_notrace()               barrier()
 
 #endif /* CONFIG_PREEMPT_COUNT */