--- /dev/null
+#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 */