Index: highlevel.c
===================================================================
--- highlevel.c	(revision 1073)
+++ highlevel.c	(working copy)
@@ -37,9 +37,18 @@
 };
 
 
+/* Double bookkeeping: hl_drivers and hl_sem_drivers are essentially
+ * the same lists, but hl_sem_list is protected by a semaphore and is
+ * used to notify highlevel drivers when we add and remove hosts. The
+ * other, hl_drivers is protected by an rw spinlock, and is used when
+ * we notify highlevel drivers of bus resets and incoming packets. */
+
 static LIST_HEAD(hl_drivers);
 static rwlock_t hl_drivers_lock = RW_LOCK_UNLOCKED;
 
+static LIST_HEAD(hl_sem_drivers);
+static DECLARE_MUTEX(hl_drivers_sem);
+
 static LIST_HEAD(addr_space);
 static rwlock_t addr_space_lock = RW_LOCK_UNLOCKED;
 
@@ -238,6 +247,10 @@
 
 	rwlock_init(&hl->host_info_lock);
 
+	down(&hl_drivers_sem);
+	list_add_tail(&hl->hl_sem_list, &hl_sem_drivers);
+	up(&hl_drivers_sem);
+
 	write_lock_irqsave(&hl_drivers_lock, flags);
         list_add_tail(&hl->hl_list, &hl_drivers);
 	write_unlock_irqrestore(&hl_drivers_lock, flags);
@@ -272,6 +285,10 @@
         list_del(&hl->hl_list);
 	write_unlock_irqrestore(&hl_drivers_lock, flags);
 
+	down(&hl_drivers_sem);
+	list_del(&hl->hl_sem_list);
+	up(&hl_drivers_sem);
+
         if (hl->remove_host) {
 		down(&hpsb_hosts_lock);
 		list_for_each(lh, &hpsb_hosts) {
@@ -391,33 +408,28 @@
 
 void highlevel_add_host(struct hpsb_host *host)
 {
-        struct list_head *entry;
         struct hpsb_highlevel *hl;
 
-        read_lock(&hl_drivers_lock);
-        list_for_each(entry, &hl_drivers) {
-                hl = list_entry(entry, struct hpsb_highlevel, hl_list);
+	down(&hl_drivers_sem);
+	list_for_each_entry(hl, &hl_sem_drivers, hl_sem_list) {
 		if (hl->add_host)
 			hl->add_host(host);
         }
-        read_unlock(&hl_drivers_lock);
+	up(&hl_drivers_sem);
 }
 
 void highlevel_remove_host(struct hpsb_host *host)
 {
-        struct list_head *entry;
         struct hpsb_highlevel *hl;
 
-	read_lock(&hl_drivers_lock);
-	list_for_each(entry, &hl_drivers) {
-                hl = list_entry(entry, struct hpsb_highlevel, hl_list);
-
+	down(&hl_drivers_sem);
+	list_for_each_entry(hl, &hl_sem_drivers, hl_sem_list) {
 		if (hl->remove_host) {
 			hl->remove_host(host);
 			hpsb_destroy_hostinfo(hl, host);
 		}
         }
-	read_unlock(&hl_drivers_lock);
+	up(&hl_drivers_sem);
 }
 
 void highlevel_host_reset(struct hpsb_host *host)
Index: highlevel.h
===================================================================
--- highlevel.h	(revision 1073)
+++ highlevel.h	(working copy)
@@ -56,6 +56,7 @@
                              int cts, u8 *data, size_t length);
 
 
+	struct list_head hl_sem_list;
 	struct list_head hl_list;
 	struct list_head addr_list;