1 files changed, 47 insertions, 0 deletions
diff --git a/c_src/include/linux/seqlock.h b/c_src/include/linux/seqlock.h
new file mode 100644
index 00000000..435420fe
--- /dev/null
+++ b/c_src/include/linux/seqlock.h
@@ -0,0 +1,47 @@
+#ifndef __LINUX_SEQLOCK_H
+#define __LINUX_SEQLOCK_H
+
+#include <linux/compiler.h>
+
+typedef struct seqcount {
+	unsigned sequence;
+} seqcount_t;
+
+static inline void seqcount_init(seqcount_t *s)
+{
+	s->sequence = 0;
+}
+
+static inline unsigned read_seqcount_begin(const seqcount_t *s)
+{
+	unsigned ret;
+
+repeat:
+	ret = READ_ONCE(s->sequence);
+	if (unlikely(ret & 1)) {
+		cpu_relax();
+		goto repeat;
+	}
+	smp_rmb();
+	return ret;
+}
+
+static inline int read_seqcount_retry(const seqcount_t *s, unsigned start)
+{
+	smp_rmb();
+	return unlikely(s->sequence != start);
+}
+
+static inline void write_seqcount_begin(seqcount_t *s)
+{
+	s->sequence++;
+	smp_wmb();
+}
+
+static inline void write_seqcount_end(seqcount_t *s)
+{
+	smp_wmb();
+	s->sequence++;
+}
+
+#endif /* __LINUX_SEQLOCK_H */