Define Linux-style <preempt.h> interface.

Use it to disable sleeping in spinlock and rcu-read regions.

Signed-off-by: Keir Fraser <keir@xen.org>

1 files changed, 33 insertions, 0 deletions

diff --git a/xen/include/xen/preempt.h b/xen/include/xen/preempt.h
new file mode 100644
index 0000000000..749bc589cb
--- /dev/null
+++ b/xen/include/xen/preempt.h
@@ -0,0 +1,33 @@
+/******************************************************************************
+ * preempt.h
+ * 
+ * Track atomic regions in the hypervisor which disallow sleeping.
+ * 
+ * Copyright (c) 2010, Keir Fraser <keir@xen.org>
+ */
+
+#ifndef __XEN_PREEMPT_H__
+#define __XEN_PREEMPT_H__
+
+#include <xen/config.h>
+#include <xen/percpu.h>
+#include <xen/irq.h>    /* in_irq() */
+#include <asm/system.h> /* local_irq_is_enabled() */
+
+DECLARE_PER_CPU(unsigned int, __preempt_count);
+
+#define preempt_count() (this_cpu(__preempt_count))
+
+#define preempt_disable() do {                  \
+    preempt_count()++;                          \
+    barrier();                                  \
+} while (0)
+
+#define preempt_enable() do {                   \
+    barrier();                                  \
+    preempt_count()--;                          \
+} while (0)
+
+#define in_atomic() (preempt_count() || in_irq() || !local_irq_is_enabled())
+
+#endif /* __XEN_PREEMPT_H__ */