From e10c4cc0a4182ed3e5f6a4a76fc72706fa459271 Mon Sep 17 00:00:00 2001
From: Hans Petter Selasky <hselasky@FreeBSD.org>
Date: Tue, 5 Jan 2016 12:22:45 +0000
Subject: [PATCH] Implement RCU mechanism using shared exclusive locks.

MFC after:	1 week
Sponsored by:	Mellanox Technologies
---
 .../linuxkpi/common/include/linux/rcupdate.h  | 76 +++++++++++++++++++
 sys/compat/linuxkpi/common/src/linux_compat.c |  9 ++-
 2 files changed, 84 insertions(+), 1 deletion(-)
 create mode 100644 sys/compat/linuxkpi/common/include/linux/rcupdate.h

diff --git a/sys/compat/linuxkpi/common/include/linux/rcupdate.h b/sys/compat/linuxkpi/common/include/linux/rcupdate.h
new file mode 100644
index 000000000000..f8e2b04bc3de
--- /dev/null
+++ b/sys/compat/linuxkpi/common/include/linux/rcupdate.h
@@ -0,0 +1,76 @@
+/*-
+ * Copyright (c) 2016 Mellanox Technologies, Ltd.
+ * All rights reserved.
+ *
+ * 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 unmodified, 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 ``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 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	_LINUX_RCUPDATE_H_
+#define	_LINUX_RCUPDATE_H_
+
+#include <sys/param.h>
+#include <sys/lock.h>
+#include <sys/sx.h>
+
+extern struct sx linux_global_rcu_lock;
+
+struct rcu_head {
+};
+
+typedef void (*rcu_callback_t)(struct rcu_head *);
+
+static inline void
+call_rcu(struct rcu_head *ptr, rcu_callback_t func)
+{
+	sx_xlock(&linux_global_rcu_lock);
+	func(ptr);
+	sx_xunlock(&linux_global_rcu_lock);
+}
+
+static inline void
+rcu_read_lock(void)
+{
+	sx_slock(&linux_global_rcu_lock);
+}
+
+static inline void
+rcu_read_unlock(void)
+{
+	sx_sunlock(&linux_global_rcu_lock);
+}
+
+static inline void
+rcu_barrier(void)
+{
+	sx_xlock(&linux_global_rcu_lock);
+	sx_xunlock(&linux_global_rcu_lock);
+}
+
+static inline void
+synchronize_rcu(void)
+{
+	sx_xlock(&linux_global_rcu_lock);
+	sx_xunlock(&linux_global_rcu_lock);
+}
+
+#endif					/* _LINUX_RCUPDATE_H_ */
diff --git a/sys/compat/linuxkpi/common/src/linux_compat.c b/sys/compat/linuxkpi/common/src/linux_compat.c
index 4d48519ff43d..efda78851b96 100644
--- a/sys/compat/linuxkpi/common/src/linux_compat.c
+++ b/sys/compat/linuxkpi/common/src/linux_compat.c
@@ -2,7 +2,7 @@
  * Copyright (c) 2010 Isilon Systems, Inc.
  * Copyright (c) 2010 iX Systems, Inc.
  * Copyright (c) 2010 Panasas, Inc.
- * Copyright (c) 2013-2015 Mellanox Technologies, Ltd.
+ * Copyright (c) 2013-2016 Mellanox Technologies, Ltd.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -65,6 +65,7 @@ __FBSDID("$FreeBSD$");
 #include <linux/netdevice.h>
 #include <linux/timer.h>
 #include <linux/workqueue.h>
+#include <linux/rcupdate.h>
 
 #include <vm/vm_pager.h>
 
@@ -84,6 +85,7 @@ struct list_head pci_drivers;
 struct list_head pci_devices;
 struct net init_net;
 spinlock_t pci_lock;
+struct sx linux_global_rcu_lock;
 
 unsigned long linux_timer_hz_mask;
 
@@ -1142,6 +1144,8 @@ linux_compat_init(void *arg)
 	struct sysctl_oid *rootoid;
 	int i;
 
+	sx_init(&linux_global_rcu_lock, "LinuxGlobalRCU");
+
 	rootoid = SYSCTL_ADD_ROOT_NODE(NULL,
 	    OID_AUTO, "sys", CTLFLAG_RD|CTLFLAG_MPSAFE, NULL, "sys");
 	kobject_init(&linux_class_root, &linux_class_ktype);
@@ -1171,6 +1175,9 @@ linux_compat_uninit(void *arg)
 	linux_kobject_kfree_name(&linux_class_root);
 	linux_kobject_kfree_name(&linux_root_device.kobj);
 	linux_kobject_kfree_name(&linux_class_misc.kobj);
+
+	synchronize_rcu();
+	sx_destroy(&linux_global_rcu_lock);
 }
 SYSUNINIT(linux_compat, SI_SUB_DRIVERS, SI_ORDER_SECOND, linux_compat_uninit, NULL);