/*-
 * Copyright (c) 1999 Michael Smith <msmith@freebsd.org>
 * 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, 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 AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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: src/sys/sys/eventhandler.h,v 1.32 2004/03/14 02:06:28 peter Exp $
 */

#ifndef SYS_EVENTHANDLER_H
#define SYS_EVENTHANDLER_H

#include <sys/lock.h>
#include <sys/ktr.h>
#include <sys/mutex.h>
#include <sys/queue.h>

struct eventhandler_entry {
	TAILQ_ENTRY(eventhandler_entry)	ee_link;
	int				ee_priority;
#define	EHE_DEAD_PRIORITY	(-1)
	void				*ee_arg;
};

struct eventhandler_list {
	char				*el_name;
	int				el_flags;
#define EHL_INITTED	(1<<0)
	u_int				el_runcount;
	struct mtx			el_lock;
	TAILQ_ENTRY(eventhandler_list)	el_link;
	TAILQ_HEAD(,eventhandler_entry)	el_entries;
};

typedef struct eventhandler_entry	*eventhandler_tag;

#define	EHL_LOCK(p)		mtx_lock(&(p)->el_lock)
#define	EHL_UNLOCK(p)		mtx_unlock(&(p)->el_lock)
#define	EHL_LOCK_ASSERT(p, x)	mtx_assert(&(p)->el_lock, x)

/*
 * Macro to invoke the handlers for a given event.
 */
#define _EVENTHANDLER_INVOKE(name, list, ...) do {			\
	struct eventhandler_entry *_ep;					\
	struct eventhandler_entry_ ## name *_t;				\
									\
	KASSERT((list)->el_flags & EHL_INITTED,				\
 	   ("eventhandler_invoke: running non-inited list"));		\
	EHL_LOCK_ASSERT((list), MA_OWNED);				\
	(list)->el_runcount++;						\
	KASSERT((list)->el_runcount > 0,				\
	    ("eventhandler_invoke: runcount overflow"));		\
	CTR0(KTR_EVH, "eventhandler_invoke(\"" __STRING(name) "\")");	\
	TAILQ_FOREACH(_ep, &((list)->el_entries), ee_link) {		\
		if (_ep->ee_priority != EHE_DEAD_PRIORITY) {		\
			EHL_UNLOCK((list));				\
			_t = (struct eventhandler_entry_ ## name *)_ep;	\
			CTR1(KTR_EVH, "eventhandler_invoke: executing %p", \
 			    (void *)_t->eh_func);			\
			_t->eh_func(_ep->ee_arg , ## __VA_ARGS__);	\
			EHL_LOCK((list));				\
		}							\
	}								\
	KASSERT((list)->el_runcount > 0,				\
	    ("eventhandler_invoke: runcount underflow"));		\
	(list)->el_runcount--;						\
	if ((list)->el_runcount == 0)					\
		eventhandler_prune_list(list);				\
	EHL_UNLOCK((list));						\
} while (0)

/*
 * Slow handlers are entirely dynamic; lists are created
 * when entries are added to them, and thus have no concept of "owner",
 *
 * Slow handlers need to be declared, but do not need to be defined. The
 * declaration must be in scope wherever the handler is to be invoked.
 */
#define EVENTHANDLER_DECLARE(name, type)				\
struct eventhandler_entry_ ## name 					\
{									\
	struct eventhandler_entry	ee;				\
	type				eh_func;			\
};									\
struct __hack

#define EVENTHANDLER_INVOKE(name, ...)					\
do {									\
	struct eventhandler_list *_el;					\
									\
	if ((_el = eventhandler_find_list(#name)) != NULL) 		\
		_EVENTHANDLER_INVOKE(name, _el , ## __VA_ARGS__);	\
} while (0)

#define EVENTHANDLER_REGISTER(name, func, arg, priority)		\
	eventhandler_register(NULL, #name, func, arg, priority)

#define EVENTHANDLER_DEREGISTER(name, tag) 				\
do {									\
	struct eventhandler_list *_el;					\
									\
	if ((_el = eventhandler_find_list(#name)) != NULL)		\
		eventhandler_deregister(_el, tag);			\
} while(0)
	

eventhandler_tag eventhandler_register(struct eventhandler_list *list, 
	    char *name, void *func, void *arg, int priority);
void	eventhandler_deregister(struct eventhandler_list *list,
	    eventhandler_tag tag);
struct eventhandler_list *eventhandler_find_list(char *name);
void	eventhandler_prune_list(struct eventhandler_list *list);

/*
 * Standard system event queues.
 */

/* Generic priority levels */
#define	EVENTHANDLER_PRI_FIRST	0
#define	EVENTHANDLER_PRI_ANY	10000
#define	EVENTHANDLER_PRI_LAST	20000

/* Shutdown events */
typedef void (*shutdown_fn)(void *, int);

#define	SHUTDOWN_PRI_FIRST	EVENTHANDLER_PRI_FIRST
#define	SHUTDOWN_PRI_DEFAULT	EVENTHANDLER_PRI_ANY
#define	SHUTDOWN_PRI_LAST	EVENTHANDLER_PRI_LAST

EVENTHANDLER_DECLARE(shutdown_pre_sync, shutdown_fn);	/* before fs sync */
EVENTHANDLER_DECLARE(shutdown_post_sync, shutdown_fn);	/* after fs sync */
EVENTHANDLER_DECLARE(shutdown_final, shutdown_fn);

/* Low memory event */
typedef void (*vm_lowmem_handler_t)(void *, int);
#define	LOWMEM_PRI_DEFAULT	EVENTHANDLER_PRI_FIRST
EVENTHANDLER_DECLARE(vm_lowmem, vm_lowmem_handler_t);

/*
 * Process events
 * process_fork and exit handlers are called without Giant.
 * exec handlers are called with Giant, but that is by accident.
 */
struct proc;

typedef void (*exitlist_fn)(void *, struct proc *);
typedef void (*forklist_fn)(void *, struct proc *, struct proc *, int);
typedef void (*execlist_fn)(void *, struct proc *);

EVENTHANDLER_DECLARE(process_exit, exitlist_fn);
EVENTHANDLER_DECLARE(process_fork, forklist_fn);
EVENTHANDLER_DECLARE(process_exec, execlist_fn);

#endif /* SYS_EVENTHANDLER_H */
