1 files changed, 147 insertions, 0 deletions
diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h
new file mode 100644
index 000000000000..e0698024667a
--- /dev/null
+++ b/include/linux/srcutiny.h
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * Sleepable Read-Copy Update mechanism for mutual exclusion,
+ *	tiny variant.
+ *
+ * Copyright (C) IBM Corporation, 2017
+ *
+ * Author: Paul McKenney <paulmck@linux.ibm.com>
+ */
+
+#ifndef _LINUX_SRCU_TINY_H
+#define _LINUX_SRCU_TINY_H
+
+#include <linux/swait.h>
+
+struct srcu_struct {
+	short srcu_lock_nesting[2];	/* srcu_read_lock() nesting depth. */
+	u8 srcu_gp_running;		/* GP workqueue running? */
+	u8 srcu_gp_waiting;		/* GP waiting for readers? */
+	unsigned long srcu_idx;		/* Current reader array element in bit 0x2. */
+	unsigned long srcu_idx_max;	/* Furthest future srcu_idx request. */
+	struct swait_queue_head srcu_wq;
+					/* Last srcu_read_unlock() wakes GP. */
+	struct rcu_head *srcu_cb_head;	/* Pending callbacks: Head. */
+	struct rcu_head **srcu_cb_tail;	/* Pending callbacks: Tail. */
+	struct work_struct srcu_work;	/* For driving grace periods. */
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lockdep_map dep_map;
+#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+};
+
+void srcu_drive_gp(struct work_struct *wp);
+
+#define __SRCU_STRUCT_INIT(name, __ignored, ___ignored, ____ignored)	\
+{									\
+	.srcu_wq = __SWAIT_QUEUE_HEAD_INITIALIZER(name.srcu_wq),	\
+	.srcu_cb_tail = &name.srcu_cb_head,				\
+	.srcu_work = __WORK_INITIALIZER(name.srcu_work, srcu_drive_gp),	\
+	__SRCU_DEP_MAP_INIT(name)					\
+}
+
+/*
+ * This odd _STATIC_ arrangement is needed for API compatibility with
+ * Tree SRCU, which needs some per-CPU data.
+ */
+#define DEFINE_SRCU(name) \
+	struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
+#define DEFINE_STATIC_SRCU(name) \
+	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
+#define DEFINE_SRCU_FAST(name) DEFINE_SRCU(name)
+#define DEFINE_STATIC_SRCU_FAST(name) \
+	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
+#define DEFINE_SRCU_FAST_UPDOWN(name) DEFINE_SRCU(name)
+#define DEFINE_STATIC_SRCU_FAST_UPDOWN(name) \
+	static struct srcu_struct name = __SRCU_STRUCT_INIT(name, name, name, name)
+
+// Dummy structure for srcu_notifier_head.
+struct srcu_usage { };
+#define __SRCU_USAGE_INIT(name) { }
+#define __init_srcu_struct_fast __init_srcu_struct
+#define __init_srcu_struct_fast_updown __init_srcu_struct
+#ifndef CONFIG_DEBUG_LOCK_ALLOC
+#define init_srcu_struct_fast init_srcu_struct
+#define init_srcu_struct_fast_updown init_srcu_struct
+#endif // #ifndef CONFIG_DEBUG_LOCK_ALLOC
+
+void synchronize_srcu(struct srcu_struct *ssp);
+
+/*
+ * Counts the new reader in the appropriate per-CPU element of the
+ * srcu_struct.  Can be invoked from irq/bh handlers, but the matching
+ * __srcu_read_unlock() must be in the same handler instance.  Returns an
+ * index that must be passed to the matching srcu_read_unlock().
+ */
+static inline int __srcu_read_lock(struct srcu_struct *ssp)
+{
+	int idx;
+
+	preempt_disable();  // Needed for PREEMPT_LAZY
+	idx = ((READ_ONCE(ssp->srcu_idx) + 1) & 0x2) >> 1;
+	WRITE_ONCE(ssp->srcu_lock_nesting[idx], READ_ONCE(ssp->srcu_lock_nesting[idx]) + 1);
+	preempt_enable();
+	return idx;
+}
+
+struct srcu_ctr;
+
+static inline bool __srcu_ptr_to_ctr(struct srcu_struct *ssp, struct srcu_ctr __percpu *scpp)
+{
+	return (int)(intptr_t)(struct srcu_ctr __force __kernel *)scpp;
+}
+
+static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ssp, int idx)
+{
+	return (struct srcu_ctr __percpu *)(intptr_t)idx;
+}
+
+static inline struct srcu_ctr __percpu *__srcu_read_lock_fast(struct srcu_struct *ssp)
+{
+	return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp));
+}
+
+static inline void __srcu_read_unlock_fast(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp)
+{
+	__srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp));
+}
+
+static inline struct srcu_ctr __percpu *__srcu_read_lock_fast_updown(struct srcu_struct *ssp)
+{
+	return __srcu_ctr_to_ptr(ssp, __srcu_read_lock(ssp));
+}
+
+static inline
+void __srcu_read_unlock_fast_updown(struct srcu_struct *ssp, struct srcu_ctr __percpu *scp)
+{
+	__srcu_read_unlock(ssp, __srcu_ptr_to_ctr(ssp, scp));
+}
+
+static inline void synchronize_srcu_expedited(struct srcu_struct *ssp)
+{
+	synchronize_srcu(ssp);
+}
+
+static inline void srcu_barrier(struct srcu_struct *ssp)
+{
+	synchronize_srcu(ssp);
+}
+
+static inline void srcu_expedite_current(struct srcu_struct *ssp) { }
+#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0)
+
+/* Defined here to avoid size increase for non-torture kernels. */
+static inline void srcu_torture_stats_print(struct srcu_struct *ssp,
+					    char *tt, char *tf)
+{
+	int idx;
+
+	idx = ((data_race(READ_ONCE(ssp->srcu_idx)) + 1) & 0x2) >> 1;
+	pr_alert("%s%s Tiny SRCU per-CPU(idx=%d): (%hd,%hd) gp: %lu->%lu\n",
+		 tt, tf, idx,
+		 data_race(READ_ONCE(ssp->srcu_lock_nesting[!idx])),
+		 data_race(READ_ONCE(ssp->srcu_lock_nesting[idx])),
+		 data_race(READ_ONCE(ssp->srcu_idx)),
+		 data_race(READ_ONCE(ssp->srcu_idx_max)));
+}
+
+#endif