Implement a new generic mechanism for attaching handler functions to

events, in order to pave the way for removing a number of the ad-hoc
implementations currently in use.

Retire the at_shutdown family of functions and replace them with
new event handler lists.

Rework kern_shutdown.c to take greater advantage of the use of event
handlers.

Reviewed by:	green

1 files changed, 140 insertions, 0 deletions

diff --git a/sys/kern/subr_eventhandler.c b/sys/kern/subr_eventhandler.c
new file mode 100644
index 0000000..2caef17
--- /dev/null
+++ b/sys/kern/subr_eventhandler.c
@@ -0,0 +1,140 @@
+/*-
+ * 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.
+ *
+ *	$Id$
+ */
+
+#include <sys/param.h>
+#include <sys/kernel.h>
+#include <sys/malloc.h>
+#include <sys/systm.h>
+#include <sys/eventhandler.h>
+
+MALLOC_DEFINE(M_EVENTHANDLER, "eventhandler", "Event handler records");
+
+/* List of 'slow' lists */
+static TAILQ_HEAD(, eventhandler_list)	eventhandler_lists;
+static int				eventhandler_lists_initted = 0;
+
+struct eventhandler_entry_generic 
+{
+    struct eventhandler_entry	ee;
+    void			(* func)(void);
+};
+
+/* 
+ * Insertion is O(n) due to the priority scan, but optimises to O(1)
+ * if all priorities are identical.
+ */
+eventhandler_tag
+eventhandler_register(struct eventhandler_list *list, char *name, 
+		      void *func, void *arg, int priority)
+{
+    struct eventhandler_entry_generic	*eg;
+    struct eventhandler_entry		*ep;
+    
+    /* avoid the need for a SYSINIT just to init the list */
+    if (!eventhandler_lists_initted) {
+	TAILQ_INIT(&eventhandler_lists);
+	eventhandler_lists_initted = 1;
+    }
+
+    /* Do we need to find/create the (slow) list? */
+    if (list == NULL) {
+	/* look for a matching, existing list */
+	list = eventhandler_find_list(name);
+
+	/* Do we need to create the list? */
+	if (list == NULL) {
+	    if ((list = malloc(sizeof(struct eventhandler_list) + strlen(name) + 1, 
+			       M_EVENTHANDLER, M_NOWAIT)) == NULL)
+		return(NULL);
+	    list->el_flags = 0;
+	    list->el_name = (char *)list + sizeof(struct eventhandler_list);
+	    strcpy(list->el_name, name);
+	    TAILQ_INSERT_HEAD(&eventhandler_lists, list, el_link);
+	}
+    }
+    if (!(list->el_flags & EHE_INITTED)) {
+	TAILQ_INIT(&list->el_entries);
+	list->el_flags = EHE_INITTED;
+    }
+    
+    /* allocate an entry for this handler, populate it */
+    if ((eg = malloc(sizeof(struct eventhandler_entry_generic), 
+		     M_EVENTHANDLER, M_NOWAIT)) == NULL)
+	return(NULL);
+    eg->func = func;
+    eg->ee.ee_arg = arg;
+    eg->ee.ee_priority = priority;
+    
+    /* sort it into the list */
+    for (ep = TAILQ_FIRST(&list->el_entries);
+	 ep != NULL; 
+	 ep = TAILQ_NEXT(ep, ee_link)) {
+	if (eg->ee.ee_priority < ep->ee_priority) {
+	    TAILQ_INSERT_BEFORE(ep, &eg->ee, ee_link);
+	    break;
+	}
+    }
+    if (ep == NULL)
+	TAILQ_INSERT_TAIL(&list->el_entries, &eg->ee, ee_link);
+    return(&eg->ee);
+}
+
+void
+eventhandler_deregister(struct eventhandler_list *list, eventhandler_tag tag)
+{
+    struct eventhandler_entry	*ep = tag;
+
+    /* XXX insert diagnostic check here? */
+    if (ep != NULL) {
+	/* remove just this entry */
+	TAILQ_REMOVE(&list->el_entries, ep, ee_link);
+	free(ep, M_EVENTHANDLER);
+    } else {
+	/* remove entire list */
+	while (!TAILQ_EMPTY(&list->el_entries)) {
+	    ep = TAILQ_FIRST(&list->el_entries);
+	    TAILQ_REMOVE(&list->el_entries, list->el_entries.tqh_first, ee_link);
+	    free(ep, M_EVENTHANDLER);
+	}
+    }
+}
+
+struct eventhandler_list *
+eventhandler_find_list(char *name)
+{
+    struct eventhandler_list	*list;
+
+    /* scan looking for the requested list */
+    for (list = TAILQ_FIRST(&eventhandler_lists); 
+	 list != NULL; 
+	 list = TAILQ_NEXT(list, el_link)) {
+	if (!strcmp(name, list->el_name))
+	    break;
+    }
+    return(list);
+}