v4.19.13 snapshot.
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
new file mode 100644
index 0000000..f35c7bf
--- /dev/null
+++ b/include/linux/notifier.h
@@ -0,0 +1,242 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Routines to manage notifier chains for passing status changes to any
+ * interested routines. We need this instead of hard coded call lists so
+ * that modules can poke their nose into the innards. The network devices
+ * needed them so here they are for the rest of you.
+ *
+ * Alan Cox <Alan.Cox@linux.org>
+ */
+
+#ifndef _LINUX_NOTIFIER_H
+#define _LINUX_NOTIFIER_H
+#include <linux/errno.h>
+#include <linux/mutex.h>
+#include <linux/rwsem.h>
+#include <linux/srcu.h>
+
+/*
+ * Notifier chains are of four types:
+ *
+ * Atomic notifier chains: Chain callbacks run in interrupt/atomic
+ * context. Callouts are not allowed to block.
+ * Blocking notifier chains: Chain callbacks run in process context.
+ * Callouts are allowed to block.
+ * Raw notifier chains: There are no restrictions on callbacks,
+ * registration, or unregistration. All locking and protection
+ * must be provided by the caller.
+ * SRCU notifier chains: A variant of blocking notifier chains, with
+ * the same restrictions.
+ *
+ * atomic_notifier_chain_register() may be called from an atomic context,
+ * but blocking_notifier_chain_register() and srcu_notifier_chain_register()
+ * must be called from a process context. Ditto for the corresponding
+ * _unregister() routines.
+ *
+ * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
+ * and srcu_notifier_chain_unregister() _must not_ be called from within
+ * the call chain.
+ *
+ * SRCU notifier chains are an alternative form of blocking notifier chains.
+ * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
+ * protection of the chain links. This means there is _very_ low overhead
+ * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
+ * As compensation, srcu_notifier_chain_unregister() is rather expensive.
+ * SRCU notifier chains should be used when the chain will be called very
+ * often but notifier_blocks will seldom be removed.
+ */
+
+struct notifier_block;
+
+typedef int (*notifier_fn_t)(struct notifier_block *nb,
+ unsigned long action, void *data);
+
+struct notifier_block {
+ notifier_fn_t notifier_call;
+ struct notifier_block __rcu *next;
+ int priority;
+};
+
+struct atomic_notifier_head {
+ spinlock_t lock;
+ struct notifier_block __rcu *head;
+};
+
+struct blocking_notifier_head {
+ struct rw_semaphore rwsem;
+ struct notifier_block __rcu *head;
+};
+
+struct raw_notifier_head {
+ struct notifier_block __rcu *head;
+};
+
+struct srcu_notifier_head {
+ struct mutex mutex;
+ struct srcu_struct srcu;
+ struct notifier_block __rcu *head;
+};
+
+#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
+ spin_lock_init(&(name)->lock); \
+ (name)->head = NULL; \
+ } while (0)
+#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
+ init_rwsem(&(name)->rwsem); \
+ (name)->head = NULL; \
+ } while (0)
+#define RAW_INIT_NOTIFIER_HEAD(name) do { \
+ (name)->head = NULL; \
+ } while (0)
+
+/* srcu_notifier_heads must be cleaned up dynamically */
+extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
+#define srcu_cleanup_notifier_head(name) \
+ cleanup_srcu_struct(&(name)->srcu);
+
+#define ATOMIC_NOTIFIER_INIT(name) { \
+ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
+ .head = NULL }
+#define BLOCKING_NOTIFIER_INIT(name) { \
+ .rwsem = __RWSEM_INITIALIZER((name).rwsem), \
+ .head = NULL }
+#define RAW_NOTIFIER_INIT(name) { \
+ .head = NULL }
+
+#define SRCU_NOTIFIER_INIT(name, pcpu) \
+ { \
+ .mutex = __MUTEX_INITIALIZER(name.mutex), \
+ .head = NULL, \
+ .srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu), \
+ }
+
+#define ATOMIC_NOTIFIER_HEAD(name) \
+ struct atomic_notifier_head name = \
+ ATOMIC_NOTIFIER_INIT(name)
+#define BLOCKING_NOTIFIER_HEAD(name) \
+ struct blocking_notifier_head name = \
+ BLOCKING_NOTIFIER_INIT(name)
+#define RAW_NOTIFIER_HEAD(name) \
+ struct raw_notifier_head name = \
+ RAW_NOTIFIER_INIT(name)
+
+#ifdef CONFIG_TREE_SRCU
+#define _SRCU_NOTIFIER_HEAD(name, mod) \
+ static DEFINE_PER_CPU(struct srcu_data, \
+ name##_head_srcu_data); \
+ mod struct srcu_notifier_head name = \
+ SRCU_NOTIFIER_INIT(name, name##_head_srcu_data)
+
+#else
+#define _SRCU_NOTIFIER_HEAD(name, mod) \
+ mod struct srcu_notifier_head name = \
+ SRCU_NOTIFIER_INIT(name, name)
+
+#endif
+
+#define SRCU_NOTIFIER_HEAD(name) \
+ _SRCU_NOTIFIER_HEAD(name, /* not static */)
+
+#define SRCU_NOTIFIER_HEAD_STATIC(name) \
+ _SRCU_NOTIFIER_HEAD(name, static)
+
+#ifdef __KERNEL__
+
+extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
+ struct notifier_block *nb);
+extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+ struct notifier_block *nb);
+extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
+ struct notifier_block *nb);
+extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
+ struct notifier_block *nb);
+
+extern int blocking_notifier_chain_cond_register(
+ struct blocking_notifier_head *nh,
+ struct notifier_block *nb);
+
+extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
+ struct notifier_block *nb);
+extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
+ struct notifier_block *nb);
+extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
+ struct notifier_block *nb);
+extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
+ struct notifier_block *nb);
+
+extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+ unsigned long val, void *v);
+extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
+ unsigned long val, void *v, int nr_to_call, int *nr_calls);
+extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+ unsigned long val, void *v);
+extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
+ unsigned long val, void *v, int nr_to_call, int *nr_calls);
+extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
+ unsigned long val, void *v);
+extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
+ unsigned long val, void *v, int nr_to_call, int *nr_calls);
+extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v);
+extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
+ unsigned long val, void *v, int nr_to_call, int *nr_calls);
+
+#define NOTIFY_DONE 0x0000 /* Don't care */
+#define NOTIFY_OK 0x0001 /* Suits me */
+#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
+#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
+ /* Bad/Veto action */
+/*
+ * Clean way to return from the notifier and stop further calls.
+ */
+#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
+
+/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
+static inline int notifier_from_errno(int err)
+{
+ if (err)
+ return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
+
+ return NOTIFY_OK;
+}
+
+/* Restore (negative) errno value from notify return value. */
+static inline int notifier_to_errno(int ret)
+{
+ ret &= ~NOTIFY_STOP_MASK;
+ return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
+}
+
+/*
+ * Declared notifiers so far. I can imagine quite a few more chains
+ * over time (eg laptop power reset chains, reboot chain (to clean
+ * device units up), device [un]mount chain, module load/unload chain,
+ * low memory chain, screenblank chain (for plug in modular screenblankers)
+ * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
+ */
+
+/* CPU notfiers are defined in include/linux/cpu.h. */
+
+/* netdevice notifiers are defined in include/linux/netdevice.h */
+
+/* reboot notifiers are defined in include/linux/reboot.h. */
+
+/* Hibernation and suspend events are defined in include/linux/suspend.h. */
+
+/* Virtual Terminal events are defined in include/linux/vt.h. */
+
+#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
+
+/* Console keyboard events.
+ * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
+ * KBD_KEYSYM. */
+#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
+#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
+#define KBD_UNICODE 0x0003 /* Keyboard unicode */
+#define KBD_KEYSYM 0x0004 /* Keyboard keysym */
+#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
+
+extern struct blocking_notifier_head reboot_notifier_list;
+
+#endif /* __KERNEL__ */
+#endif /* _LINUX_NOTIFIER_H */