1 files changed, 94 insertions, 0 deletions
diff --git a/include/linux/rcu_sync.h b/include/linux/rcu_sync.h
new file mode 100644
index 000000000000..cb044df2e21c
--- /dev/null
+++ b/include/linux/rcu_sync.h
@@ -0,0 +1,94 @@
+/*
+ * RCU-based infrastructure for lightweight reader-writer locking
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you can access it online at
+ * http://www.gnu.org/licenses/gpl-2.0.html.
+ *
+ * Copyright (c) 2015, Red Hat, Inc.
+ *
+ * Author: Oleg Nesterov <oleg@redhat.com>
+ */
+
+#ifndef _LINUX_RCU_SYNC_H_
+#define _LINUX_RCU_SYNC_H_
+
+#include <linux/wait.h>
+#include <linux/rcupdate.h>
+
+/* Structure to mediate between updaters and fastpath-using readers.  */
+struct rcu_sync {
+	int			gp_state;
+	int			gp_count;
+	wait_queue_head_t	gp_wait;
+
+	int			cb_state;
+	struct rcu_head		cb_head;
+
+	void (*sync)(void);
+	void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
+};
+
+#define ___RCU_SYNC_INIT(name)						\
+	.gp_state = 0,							\
+	.gp_count = 0,							\
+	.gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait),		\
+	.cb_state = 0
+
+#define __RCU_SCHED_SYNC_INIT(name) {					\
+	___RCU_SYNC_INIT(name),						\
+	.sync = synchronize_sched,					\
+	.call = call_rcu_sched,						\
+}
+
+#define __RCU_BH_SYNC_INIT(name) {					\
+	___RCU_SYNC_INIT(name),						\
+	.sync = synchronize_rcu_bh,					\
+	.call = call_rcu_bh,						\
+}
+
+#define __RCU_SYNC_INIT(name) {						\
+	___RCU_SYNC_INIT(name),						\
+	.sync = synchronize_rcu,					\
+	.call = call_rcu,						\
+}
+
+#define DEFINE_RCU_SCHED_SYNC(name)					\
+	struct rcu_sync name = __RCU_SCHED_SYNC_INIT(name)
+
+#define DEFINE_RCU_BH_SYNC(name)					\
+	struct rcu_sync name = __RCU_BH_SYNC_INIT(name)
+
+#define DEFINE_RCU_SYNC(name)						\
+	struct rcu_sync name = __RCU_SYNC_INIT(name)
+
+/**
+ * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * Returns true if readers are permitted to use their fastpaths.
+ * Must be invoked within an RCU read-side critical section whose
+ * flavor matches that of the rcu_sync struture.
+ */
+static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
+{
+	return !rsp->gp_state; /* GP_IDLE */
+}
+
+enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
+
+extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
+extern void rcu_sync_enter(struct rcu_sync *);
+extern void rcu_sync_exit(struct rcu_sync *);
+
+#endif /* _LINUX_RCU_SYNC_H_ */