1 files changed, 107 insertions, 0 deletions
diff --git a/freebsd/sys/sys/seqc.h b/freebsd/sys/sys/seqc.h
new file mode 100644
index 00000000..00e4cc3c
--- /dev/null
+++ b/freebsd/sys/sys/seqc.h
@@ -0,0 +1,107 @@
+/*-
+ * Copyright (c) 2014 Mateusz Guzik <mjg@FreeBSD.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+
+#ifndef _SYS_SEQC_H_
+#define _SYS_SEQC_H_
+
+#ifdef _KERNEL
+#include <sys/systm.h>
+#endif
+#include <sys/types.h>
+
+/*
+ * seqc_t may be included in structs visible to userspace
+ */
+typedef uint32_t seqc_t;
+
+#ifdef _KERNEL
+
+/* A hack to get MPASS macro */
+#include <sys/lock.h>
+
+#include <machine/cpu.h>
+
+static __inline bool
+seqc_in_modify(seqc_t seqcp)
+{
+
+	return (seqcp & 1);
+}
+
+static __inline void
+seqc_write_begin(seqc_t *seqcp)
+{
+
+	critical_enter();
+	MPASS(!seqc_in_modify(*seqcp));
+	*seqcp += 1;
+	atomic_thread_fence_rel();
+}
+
+static __inline void
+seqc_write_end(seqc_t *seqcp)
+{
+
+	atomic_store_rel_int(seqcp, *seqcp + 1);
+	MPASS(!seqc_in_modify(*seqcp));
+	critical_exit();
+}
+
+static __inline seqc_t
+seqc_read(const seqc_t *seqcp)
+{
+	seqc_t ret;
+
+	for (;;) {
+		ret = atomic_load_acq_int(__DECONST(seqc_t *, seqcp));
+		if (__predict_false(seqc_in_modify(ret))) {
+			cpu_spinwait();
+			continue;
+		}
+		break;
+	}
+
+	return (ret);
+}
+
+static __inline bool
+seqc_consistent_nomb(const seqc_t *seqcp, seqc_t oldseqc)
+{
+
+	return (*seqcp == oldseqc);
+}
+
+static __inline bool
+seqc_consistent(const seqc_t *seqcp, seqc_t oldseqc)
+{
+
+	atomic_thread_fence_acq();
+	return (seqc_consistent_nomb(seqcp, oldseqc));
+}
+
+#endif	/* _KERNEL */
+#endif	/* _SYS_SEQC_H_ */