From 8e4bff4cab0ddac6060645b0715210484d02ff40 Mon Sep 17 00:00:00 2001
From: Yuval Adam <_@yuv.al>
Date: Wed, 30 Aug 2017 08:25:59 +0000
Subject: Initial file dump from open source release

---
 include/linux/lglock.h | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 include/linux/lglock.h

(limited to 'include/linux/lglock.h')

diff --git a/include/linux/lglock.h b/include/linux/lglock.h
new file mode 100644
index 00000000..0d24e932
--- /dev/null
+++ b/include/linux/lglock.h
@@ -0,0 +1,70 @@
+/*
+ * Specialised local-global spinlock. Can only be declared as global variables
+ * to avoid overhead and keep things simple (and we don't want to start using
+ * these inside dynamically allocated structures).
+ *
+ * "local/global locks" (lglocks) can be used to:
+ *
+ * - Provide fast exclusive access to per-CPU data, with exclusive access to
+ *   another CPU's data allowed but possibly subject to contention, and to
+ *   provide very slow exclusive access to all per-CPU data.
+ * - Or to provide very fast and scalable read serialisation, and to provide
+ *   very slow exclusive serialisation of data (not necessarily per-CPU data).
+ *
+ * Brlocks are also implemented as a short-hand notation for the latter use
+ * case.
+ *
+ * Copyright 2009, 2010, Nick Piggin, Novell Inc.
+ */
+#ifndef __LINUX_LGLOCK_H
+#define __LINUX_LGLOCK_H
+
+#include <linux/spinlock.h>
+#include <linux/lockdep.h>
+#include <linux/percpu.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
+
+/* can make br locks by using local lock for read side, global lock for write */
+#define br_lock_init(name)	lg_lock_init(name, #name)
+#define br_read_lock(name)	lg_local_lock(name)
+#define br_read_unlock(name)	lg_local_unlock(name)
+#define br_write_lock(name)	lg_global_lock(name)
+#define br_write_unlock(name)	lg_global_unlock(name)
+
+#define DEFINE_BRLOCK(name)		DEFINE_LGLOCK(name)
+#define DEFINE_STATIC_BRLOCK(name)	DEFINE_STATIC_LGLOCK(name)
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+#define LOCKDEP_INIT_MAP lockdep_init_map
+#else
+#define LOCKDEP_INIT_MAP(a, b, c, d)
+#endif
+
+struct lglock {
+	arch_spinlock_t __percpu *lock;
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+	struct lock_class_key lock_key;
+	struct lockdep_map    lock_dep_map;
+#endif
+};
+
+#define DEFINE_LGLOCK(name)						\
+	static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)		\
+	= __ARCH_SPIN_LOCK_UNLOCKED;					\
+	struct lglock name = { .lock = &name ## _lock }
+
+#define DEFINE_STATIC_LGLOCK(name)					\
+	static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)		\
+	= __ARCH_SPIN_LOCK_UNLOCKED;					\
+	static struct lglock name = { .lock = &name ## _lock }
+
+void lg_lock_init(struct lglock *lg, char *name);
+void lg_local_lock(struct lglock *lg);
+void lg_local_unlock(struct lglock *lg);
+void lg_local_lock_cpu(struct lglock *lg, int cpu);
+void lg_local_unlock_cpu(struct lglock *lg, int cpu);
+void lg_global_lock(struct lglock *lg);
+void lg_global_unlock(struct lglock *lg);
+
+#endif
-- 
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