v4.19.13 snapshot.
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
new file mode 100644
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--- /dev/null
+++ b/include/linux/srcutree.h
@@ -0,0 +1,144 @@
+/*
+ * Sleepable Read-Copy Update mechanism for mutual exclusion,
+ * tree variant.
+ *
+ * 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) IBM Corporation, 2017
+ *
+ * Author: Paul McKenney <paulmck@us.ibm.com>
+ */
+
+#ifndef _LINUX_SRCU_TREE_H
+#define _LINUX_SRCU_TREE_H
+
+#include <linux/rcu_node_tree.h>
+#include <linux/completion.h>
+
+struct srcu_node;
+struct srcu_struct;
+
+/*
+ * Per-CPU structure feeding into leaf srcu_node, similar in function
+ * to rcu_node.
+ */
+struct srcu_data {
+ /* Read-side state. */
+ unsigned long srcu_lock_count[2]; /* Locks per CPU. */
+ unsigned long srcu_unlock_count[2]; /* Unlocks per CPU. */
+
+ /* Update-side state. */
+ spinlock_t __private lock ____cacheline_internodealigned_in_smp;
+ struct rcu_segcblist srcu_cblist; /* List of callbacks.*/
+ unsigned long srcu_gp_seq_needed; /* Furthest future GP needed. */
+ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
+ bool srcu_cblist_invoking; /* Invoking these CBs? */
+ struct delayed_work work; /* Context for CB invoking. */
+ struct rcu_head srcu_barrier_head; /* For srcu_barrier() use. */
+ struct srcu_node *mynode; /* Leaf srcu_node. */
+ unsigned long grpmask; /* Mask for leaf srcu_node */
+ /* ->srcu_data_have_cbs[]. */
+ int cpu;
+ struct srcu_struct *sp;
+};
+
+/*
+ * Node in SRCU combining tree, similar in function to rcu_data.
+ */
+struct srcu_node {
+ spinlock_t __private lock;
+ unsigned long srcu_have_cbs[4]; /* GP seq for children */
+ /* having CBs, but only */
+ /* is > ->srcu_gq_seq. */
+ unsigned long srcu_data_have_cbs[4]; /* Which srcu_data structs */
+ /* have CBs for given GP? */
+ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
+ struct srcu_node *srcu_parent; /* Next up in tree. */
+ int grplo; /* Least CPU for node. */
+ int grphi; /* Biggest CPU for node. */
+};
+
+/*
+ * Per-SRCU-domain structure, similar in function to rcu_state.
+ */
+struct srcu_struct {
+ struct srcu_node node[NUM_RCU_NODES]; /* Combining tree. */
+ struct srcu_node *level[RCU_NUM_LVLS + 1];
+ /* First node at each level. */
+ struct mutex srcu_cb_mutex; /* Serialize CB preparation. */
+ spinlock_t __private lock; /* Protect counters */
+ struct mutex srcu_gp_mutex; /* Serialize GP work. */
+ unsigned int srcu_idx; /* Current rdr array element. */
+ unsigned long srcu_gp_seq; /* Grace-period seq #. */
+ unsigned long srcu_gp_seq_needed; /* Latest gp_seq needed. */
+ unsigned long srcu_gp_seq_needed_exp; /* Furthest future exp GP. */
+ unsigned long srcu_last_gp_end; /* Last GP end timestamp (ns) */
+ struct srcu_data __percpu *sda; /* Per-CPU srcu_data array. */
+ unsigned long srcu_barrier_seq; /* srcu_barrier seq #. */
+ struct mutex srcu_barrier_mutex; /* Serialize barrier ops. */
+ struct completion srcu_barrier_completion;
+ /* Awaken barrier rq at end. */
+ atomic_t srcu_barrier_cpu_cnt; /* # CPUs not yet posting a */
+ /* callback for the barrier */
+ /* operation. */
+ struct delayed_work work;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+};
+
+/* Values for state variable (bottom bits of ->srcu_gp_seq). */
+#define SRCU_STATE_IDLE 0
+#define SRCU_STATE_SCAN1 1
+#define SRCU_STATE_SCAN2 2
+
+#define __SRCU_STRUCT_INIT(name, pcpu_name) \
+ { \
+ .sda = &pcpu_name, \
+ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
+ .srcu_gp_seq_needed = 0 - 1, \
+ __SRCU_DEP_MAP_INIT(name) \
+ }
+
+/*
+ * Define and initialize a srcu struct at build time.
+ * Do -not- call init_srcu_struct() nor cleanup_srcu_struct() on it.
+ *
+ * Note that although DEFINE_STATIC_SRCU() hides the name from other
+ * files, the per-CPU variable rules nevertheless require that the
+ * chosen name be globally unique. These rules also prohibit use of
+ * DEFINE_STATIC_SRCU() within a function. If these rules are too
+ * restrictive, declare the srcu_struct manually. For example, in
+ * each file:
+ *
+ * static struct srcu_struct my_srcu;
+ *
+ * Then, before the first use of each my_srcu, manually initialize it:
+ *
+ * init_srcu_struct(&my_srcu);
+ *
+ * See include/linux/percpu-defs.h for the rules on per-CPU variables.
+ */
+#define __DEFINE_SRCU(name, is_static) \
+ static DEFINE_PER_CPU(struct srcu_data, name##_srcu_data);\
+ is_static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name##_srcu_data)
+#define DEFINE_SRCU(name) __DEFINE_SRCU(name, /* not static */)
+#define DEFINE_STATIC_SRCU(name) __DEFINE_SRCU(name, static)
+
+void synchronize_srcu_expedited(struct srcu_struct *sp);
+void srcu_barrier(struct srcu_struct *sp);
+void srcu_torture_stats_print(struct srcu_struct *sp, char *tt, char *tf);
+
+#endif