[PATCH] ipmi: use refcount in message handler

This patch is rather large, but it really can't be done in smaller chunks
easily and I believe it is an important change.  This has been out and tested
for a while in the latest IPMI driver release.  There are no functional
changes, just changes as necessary to convert the locking over (and a few
minor style updates).

The IPMI driver uses read/write locks to ensure that things exist while they
are in use.  This is bad from a number of points of view.  This patch removes
the rwlocks and uses refcounts and RCU lists to manage what the locks did.
Signed-off-by: Corey Minyard <minyard@acm.org>
Cc: Matt Domsch <Matt_Domsch@dell.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/char/ipmi/ipmi_msghandler.c

@@ -38,13 +38,13 @@
 #include <linux/sched.h>
 #include <linux/poll.h>
 #include <linux/spinlock.h>
-#include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/ipmi.h>
 #include <linux/ipmi_smi.h>
 #include <linux/notifier.h>
 #include <linux/init.h>
 #include <linux/proc_fs.h>
+#include <linux/rcupdate.h>
 
 #define PFX "IPMI message handler: "
 
@@ -65,10 +65,19 @@ struct proc_dir_entry *proc_ipmi_root = NULL;
    the max message timer.  This is in milliseconds. */
 #define MAX_MSG_TIMEOUT		60000
 
+
+/*
+ * The main "user" data structure.
+ */
 struct ipmi_user
 {
 	struct list_head link;
 
+	/* Set to "0" when the user is destroyed. */
+	int valid;
+
+	struct kref refcount;
+
 	/* The upper layer that handles receive messages. */
 	struct ipmi_user_hndl *handler;
 	void             *handler_data;
@@ -87,6 +96,15 @@ struct cmd_rcvr
 	ipmi_user_t   user;
 	unsigned char netfn;
 	unsigned char cmd;
+
+	/*
+	 * This is used to form a linked lised during mass deletion.
+	 * Since this is in an RCU list, we cannot use the link above
+	 * or change any data until the RCU period completes.  So we
+	 * use this next variable during mass deletion so we can have
+	 * a list and don't have to wait and restart the search on
+	 * every individual deletion of a command. */
+	struct cmd_rcvr *next;
 };
 
 struct seq_table
@@ -150,12 +168,10 @@ struct ipmi_smi
 	/* What interface number are we? */
 	int intf_num;
 
-	/* The list of upper layers that are using me.  We read-lock
-           this when delivering messages to the upper layer to keep
-           the user from going away while we are processing the
-           message.  This means that you cannot add or delete a user
-           from the receive callback. */
-	rwlock_t                users_lock;
+	struct kref refcount;
+
+	/* The list of upper layers that are using me.  seq_lock
+	 * protects this. */
 	struct list_head users;
 
 	/* Used for wake ups at startup. */
@@ -193,7 +209,7 @@ struct ipmi_smi
 
 	/* The list of command receivers that are registered for commands
 	   on this interface. */
-	rwlock_t	 cmd_rcvr_lock;
+	spinlock_t       cmd_rcvrs_lock;
 	struct list_head cmd_rcvrs;
 
 	/* Events that were queues because no one was there to receive
@@ -296,16 +312,17 @@ struct ipmi_smi
 	unsigned int events;
 };
 
+/* Used to mark an interface entry that cannot be used but is not a
+ * free entry, either, primarily used at creation and deletion time so
+ * a slot doesn't get reused too quickly. */
+#define IPMI_INVALID_INTERFACE_ENTRY ((ipmi_smi_t) ((long) 1))
+#define IPMI_INVALID_INTERFACE(i) (((i) == NULL) \
+				   || (i == IPMI_INVALID_INTERFACE_ENTRY))
+
 #define MAX_IPMI_INTERFACES 4
 static ipmi_smi_t ipmi_interfaces[MAX_IPMI_INTERFACES];
 
-/* Used to keep interfaces from going away while operations are
-   operating on interfaces.  Grab read if you are not modifying the
-   interfaces, write if you are. */
-static DECLARE_RWSEM(interfaces_sem);
-
-/* Directly protects the ipmi_interfaces data structure.  This is
-   claimed in the timer interrupt. */
+/* Directly protects the ipmi_interfaces data structure. */
 static DEFINE_SPINLOCK(interfaces_lock);
 
 /* List of watchers that want to know when smi's are added and
@@ -313,20 +330,73 @@ static DEFINE_SPINLOCK(interfaces_lock);
 static struct list_head smi_watchers = LIST_HEAD_INIT(smi_watchers);
 static DECLARE_RWSEM(smi_watchers_sem);
 
+
+static void free_recv_msg_list(struct list_head *q)
+{
+	struct ipmi_recv_msg *msg, *msg2;
+
+	list_for_each_entry_safe(msg, msg2, q, link) {
+		list_del(&msg->link);
+		ipmi_free_recv_msg(msg);
+	}
+}
+
+static void clean_up_interface_data(ipmi_smi_t intf)
+{
+	int              i;
+	struct cmd_rcvr  *rcvr, *rcvr2;
+	unsigned long    flags;
+	struct list_head list;
+
+	free_recv_msg_list(&intf->waiting_msgs);
+	free_recv_msg_list(&intf->waiting_events);
+
+	/* Wholesale remove all the entries from the list in the
+	 * interface and wait for RCU to know that none are in use. */
+	spin_lock_irqsave(&intf->cmd_rcvrs_lock, flags);
+	list_add_rcu(&list, &intf->cmd_rcvrs);
+	list_del_rcu(&intf->cmd_rcvrs);
+	spin_unlock_irqrestore(&intf->cmd_rcvrs_lock, flags);
+	synchronize_rcu();
+
+	list_for_each_entry_safe(rcvr, rcvr2, &list, link)
+		kfree(rcvr);
+
+	for (i = 0; i < IPMI_IPMB_NUM_SEQ; i++) {
+		if ((intf->seq_table[i].inuse)
+		    && (intf->seq_table[i].recv_msg))
+		{
+			ipmi_free_recv_msg(intf->seq_table[i].recv_msg);
+		}
+	}
+}
+
+static void intf_free(struct kref *ref)
+{
+	ipmi_smi_t intf = container_of(ref, struct ipmi_smi, refcount);
+
+	clean_up_interface_data(intf);
+	kfree(intf);
+}
+
 int ipmi_smi_watcher_register(struct ipmi_smi_watcher *watcher)
 {
 	int           i;
+	unsigned long flags;
 
-	down_read(&interfaces_sem);
 	down_write(&smi_watchers_sem);
 	list_add(&(watcher->link), &smi_watchers);
+	up_write(&smi_watchers_sem);
+	spin_lock_irqsave(&interfaces_lock, flags);
 	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
-		if (ipmi_interfaces[i] != NULL) {
+		ipmi_smi_t intf = ipmi_interfaces[i];
+		if (IPMI_INVALID_INTERFACE(intf))
+			continue;
+		spin_unlock_irqrestore(&interfaces_lock, flags);
 		watcher->new_smi(i);
+		spin_lock_irqsave(&interfaces_lock, flags);
 	}
-	}
-	up_write(&smi_watchers_sem);
-	up_read(&interfaces_sem);
+	spin_unlock_irqrestore(&interfaces_lock, flags);
 	return 0;
 }
 
@@ -471,8 +541,8 @@ static void deliver_response(struct ipmi_recv_msg *msg)
 		}
 		ipmi_free_recv_msg(msg);
 	} else {
-		msg->user->handler->ipmi_recv_hndl(msg,
-						   msg->user->handler_data);
+		ipmi_user_t user = msg->user;
+		user->handler->ipmi_recv_hndl(msg, user->handler_data);
 	}
 }
 
@@ -662,15 +732,18 @@ int ipmi_create_user(unsigned int          if_num,
 	if (! new_user)
 		return -ENOMEM;
 
-	down_read(&interfaces_sem);
-	if ((if_num >= MAX_IPMI_INTERFACES) || ipmi_interfaces[if_num] == NULL)
-	{
-		rv = -EINVAL;
-		goto out_unlock;
+	spin_lock_irqsave(&interfaces_lock, flags);
+	intf = ipmi_interfaces[if_num];
+	if ((if_num >= MAX_IPMI_INTERFACES) || IPMI_INVALID_INTERFACE(intf)) {
+		spin_unlock_irqrestore(&interfaces_lock, flags);
+		return -EINVAL;
 	}
 
-	intf = ipmi_interfaces[if_num];
+	/* Note that each existing user holds a refcount to the interface. */
+	kref_get(&intf->refcount);
+	spin_unlock_irqrestore(&interfaces_lock, flags);
 
+	kref_init(&new_user->refcount);
 	new_user->handler = handler;
 	new_user->handler_data = handler_data;
 	new_user->intf = intf;
@@ -678,98 +751,92 @@ int ipmi_create_user(unsigned int          if_num,
 
 	if (!try_module_get(intf->handlers->owner)) {
 		rv = -ENODEV;
-		goto out_unlock;
+		goto out_err;
 	}
 
 	if (intf->handlers->inc_usecount) {
 		rv = intf->handlers->inc_usecount(intf->send_info);
 		if (rv) {
 			module_put(intf->handlers->owner);
-			goto out_unlock;
+			goto out_err;
 		}
 	}
 
-	write_lock_irqsave(&intf->users_lock, flags);
-	list_add_tail(&new_user->link, &intf->users);
-	write_unlock_irqrestore(&intf->users_lock, flags);
-
- out_unlock:	
-	if (rv) {
-		kfree(new_user);
-	} else {
+	new_user->valid = 1;
+	spin_lock_irqsave(&intf->seq_lock, flags);
+	list_add_rcu(&new_user->link, &intf->users);
+	spin_unlock_irqrestore(&intf->seq_lock, flags);
 	*user = new_user;
-	}
+	return 0;
 
-	up_read(&interfaces_sem);
+ out_err:
+	kfree(new_user);
+	kref_put(&intf->refcount, intf_free);
 	return rv;
 }
 
-static int ipmi_destroy_user_nolock(ipmi_user_t user)
+static void free_user(struct kref *ref)
+{
+	ipmi_user_t user = container_of(ref, struct ipmi_user, refcount);
+	kfree(user);
+}
+
+int ipmi_destroy_user(ipmi_user_t user)
 {
 	int              rv = -ENODEV;
-	ipmi_user_t      t_user;
-	struct cmd_rcvr  *rcvr, *rcvr2;
+	ipmi_smi_t       intf = user->intf;
 	int              i;
 	unsigned long    flags;
+	struct cmd_rcvr  *rcvr;
+	struct list_head *entry1, *entry2;
+	struct cmd_rcvr  *rcvrs = NULL;
 
-	/* Find the user and delete them from the list. */
-	list_for_each_entry(t_user, &(user->intf->users), link) {
-		if (t_user == user) {
-			list_del(&t_user->link);
-			rv = 0;
-			break;
-		}
-	}
+	user->valid = 1;
 
-	if (rv) {
-		goto out_unlock;
-	}
+	/* Remove the user from the interface's sequence table. */
+	spin_lock_irqsave(&intf->seq_lock, flags);
+	list_del_rcu(&user->link);
 
-	/* Remove the user from the interfaces sequence table. */
-	spin_lock_irqsave(&(user->intf->seq_lock), flags);
 	for (i = 0; i < IPMI_IPMB_NUM_SEQ; i++) {
-		if (user->intf->seq_table[i].inuse
-		    && (user->intf->seq_table[i].recv_msg->user == user))
+		if (intf->seq_table[i].inuse
+		    && (intf->seq_table[i].recv_msg->user == user))
 		{
-			user->intf->seq_table[i].inuse = 0;
+			intf->seq_table[i].inuse = 0;
 		}
 	}
-	spin_unlock_irqrestore(&(user->intf->seq_lock), flags);
+	spin_unlock_irqrestore(&intf->seq_lock, flags);
 
-	/* Remove the user from the command receiver's table. */
-	write_lock_irqsave(&(user->intf->cmd_rcvr_lock), flags);
-	list_for_each_entry_safe(rcvr, rcvr2, &(user->intf->cmd_rcvrs), link) {
+	/*
+	 * Remove the user from the command receiver's table.  First
+	 * we build a list of everything (not using the standard link,
+	 * since other things may be using it till we do
+	 * synchronize_rcu()) then free everything in that list.
+	 */
+	spin_lock_irqsave(&intf->cmd_rcvrs_lock, flags);
+	list_for_each_safe_rcu(entry1, entry2, &intf->cmd_rcvrs) {
+		rcvr = list_entry(entry1, struct cmd_rcvr, link);
 		if (rcvr->user == user) {
-			list_del(&rcvr->link);
-			kfree(rcvr);
+			list_del_rcu(&rcvr->link);
+			rcvr->next = rcvrs;
+			rcvrs = rcvr;
 		}
 	}
-	write_unlock_irqrestore(&(user->intf->cmd_rcvr_lock), flags);
-
-	kfree(user);
-
- out_unlock:
-
-	return rv;
-}
-
-int ipmi_destroy_user(ipmi_user_t user)
-{
-	int           rv;
-	ipmi_smi_t    intf = user->intf;
-	unsigned long flags;
+	spin_unlock_irqrestore(&intf->cmd_rcvrs_lock, flags);
+	synchronize_rcu();
+	while (rcvrs) {
+		rcvr = rcvrs;
+		rcvrs = rcvr->next;
+		kfree(rcvr);
+	}
 
-	down_read(&interfaces_sem);
-	write_lock_irqsave(&intf->users_lock, flags);
-	rv = ipmi_destroy_user_nolock(user);
-	if (!rv) {
 	module_put(intf->handlers->owner);
 	if (intf->handlers->dec_usecount)
 		intf->handlers->dec_usecount(intf->send_info);
-	}
 
-	write_unlock_irqrestore(&intf->users_lock, flags);
-	up_read(&interfaces_sem);
+	kref_put(&intf->refcount, intf_free);
+
+	kref_put(&user->refcount, free_user);
+
 	return rv;
 }
 
@@ -824,61 +891,77 @@ int ipmi_get_my_LUN(ipmi_user_t   user,
 int ipmi_set_gets_events(ipmi_user_t user, int val)
 {
 	unsigned long        flags;
+	ipmi_smi_t           intf = user->intf;
 	struct ipmi_recv_msg *msg, *msg2;
+	struct list_head     msgs;
 
-	read_lock(&(user->intf->users_lock));
-	spin_lock_irqsave(&(user->intf->events_lock), flags);
+	INIT_LIST_HEAD(&msgs);
+
+	spin_lock_irqsave(&intf->events_lock, flags);
 	user->gets_events = val;
 
 	if (val) {
 		/* Deliver any queued events. */
-		list_for_each_entry_safe(msg, msg2, &(user->intf->waiting_events), link) {
+		list_for_each_entry_safe(msg, msg2, &intf->waiting_events, link) {
 			list_del(&msg->link);
+			list_add_tail(&msg->link, &msgs);
+		}
+	}
+
+	/* Hold the events lock while doing this to preserve order. */
+	list_for_each_entry_safe(msg, msg2, &msgs, link) {
 		msg->user = user;
+		kref_get(&user->refcount);
 		deliver_response(msg);
 	}
-	}
 
-	spin_unlock_irqrestore(&(user->intf->events_lock), flags);
-	read_unlock(&(user->intf->users_lock));
+	spin_unlock_irqrestore(&intf->events_lock, flags);
 
 	return 0;
 }
 
+static struct cmd_rcvr *find_cmd_rcvr(ipmi_smi_t    intf,
+				      unsigned char netfn,
+				      unsigned char cmd)
+{
+	struct cmd_rcvr *rcvr;
+
+	list_for_each_entry_rcu(rcvr, &intf->cmd_rcvrs, link) {
+		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd))
+			return rcvr;
+	}
+	return NULL;
+}
+
 int ipmi_register_for_cmd(ipmi_user_t   user,
 			  unsigned char netfn,
 			  unsigned char cmd)
 {
-	struct cmd_rcvr  *cmp;
-	unsigned long    flags;
+	ipmi_smi_t      intf = user->intf;
 	struct cmd_rcvr *rcvr;
+	struct cmd_rcvr *entry;
 	int             rv = 0;
 
 
 	rcvr = kmalloc(sizeof(*rcvr), GFP_KERNEL);
 	if (! rcvr)
 		return -ENOMEM;
-
-	read_lock(&(user->intf->users_lock));
-	write_lock_irqsave(&(user->intf->cmd_rcvr_lock), flags);
-	/* Make sure the command/netfn is not already registered. */
-	list_for_each_entry(cmp, &(user->intf->cmd_rcvrs), link) {
-		if ((cmp->netfn == netfn) && (cmp->cmd == cmd)) {
-			rv = -EBUSY;
-			break;
-		}
-	}
-
-	if (! rv) {
 	rcvr->cmd = cmd;
 	rcvr->netfn = netfn;
 	rcvr->user = user;
-		list_add_tail(&(rcvr->link), &(user->intf->cmd_rcvrs));
+
+	spin_lock_irq(&intf->cmd_rcvrs_lock);
+	/* Make sure the command/netfn is not already registered. */
+	entry = find_cmd_rcvr(intf, netfn, cmd);
+	if (entry) {
+		rv = -EBUSY;
+		goto out_unlock;
 	}
 
-	write_unlock_irqrestore(&(user->intf->cmd_rcvr_lock), flags);
-	read_unlock(&(user->intf->users_lock));
+	list_add_rcu(&rcvr->link, &intf->cmd_rcvrs);
 
+ out_unlock:
+	spin_unlock_irq(&intf->cmd_rcvrs_lock);
 	if (rv)
 		kfree(rcvr);
 
@@ -889,31 +972,28 @@ int ipmi_unregister_for_cmd(ipmi_user_t   user,
 			    unsigned char netfn,
 			    unsigned char cmd)
 {
-	unsigned long    flags;
+	ipmi_smi_t      intf = user->intf;
 	struct cmd_rcvr *rcvr;
-	int              rv = -ENOENT;
 
-	read_lock(&(user->intf->users_lock));
-	write_lock_irqsave(&(user->intf->cmd_rcvr_lock), flags);
+	spin_lock_irq(&intf->cmd_rcvrs_lock);
 	/* Make sure the command/netfn is not already registered. */
-	list_for_each_entry(rcvr, &(user->intf->cmd_rcvrs), link) {
-		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)) {
-			rv = 0;
-			list_del(&rcvr->link);
+	rcvr = find_cmd_rcvr(intf, netfn, cmd);
+	if ((rcvr) && (rcvr->user == user)) {
+		list_del_rcu(&rcvr->link);
+		spin_unlock_irq(&intf->cmd_rcvrs_lock);
+		synchronize_rcu();
 		kfree(rcvr);
-			break;
-		}
+		return 0;
+	} else {
+		spin_unlock_irq(&intf->cmd_rcvrs_lock);
+		return -ENOENT;
 	}
-	write_unlock_irqrestore(&(user->intf->cmd_rcvr_lock), flags);
-	read_unlock(&(user->intf->users_lock));
-
-	return rv;
 }
 
 void ipmi_user_set_run_to_completion(ipmi_user_t user, int val)
 {
-	user->intf->handlers->set_run_to_completion(user->intf->send_info,
-						    val);
+	ipmi_smi_t intf = user->intf;
+	intf->handlers->set_run_to_completion(intf->send_info, val);
 }
 
 static unsigned char
@@ -1010,7 +1090,7 @@ static inline void format_lan_msg(struct ipmi_smi_msg   *smi_msg,
    supplied in certain circumstances (mainly at panic time).  If
    messages are supplied, they will be freed, even if an error
    occurs. */
-static inline int i_ipmi_request(ipmi_user_t          user,
+static int i_ipmi_request(ipmi_user_t          user,
 			  ipmi_smi_t           intf,
 			  struct ipmi_addr     *addr,
 			  long                 msgid,
@@ -1051,6 +1131,8 @@ static inline int i_ipmi_request(ipmi_user_t          user,
 	}
 
 	recv_msg->user = user;
+	if (user)
+		kref_get(&user->refcount);
 	recv_msg->msgid = msgid;
 	/* Store the message to send in the receive message so timeout
 	   responses can get the proper response data. */
@@ -1725,11 +1807,11 @@ int ipmi_register_smi(struct ipmi_smi_handlers *handlers,
 		      unsigned char            version_major,
 		      unsigned char            version_minor,
 		      unsigned char            slave_addr,
-		      ipmi_smi_t               *intf)
+		      ipmi_smi_t               *new_intf)
 {
 	int              i, j;
 	int              rv;
-	ipmi_smi_t       new_intf;
+	ipmi_smi_t       intf;
 	unsigned long    flags;
 
 
@@ -1745,189 +1827,142 @@ int ipmi_register_smi(struct ipmi_smi_handlers *handlers,
 			return -ENODEV;
 	}
 
-	new_intf = kmalloc(sizeof(*new_intf), GFP_KERNEL);
-	if (!new_intf)
+	intf = kmalloc(sizeof(*intf), GFP_KERNEL);
+	if (!intf)
 		return -ENOMEM;
-	memset(new_intf, 0, sizeof(*new_intf));
-
-	new_intf->proc_dir = NULL;
-
-	rv = -ENOMEM;
-
-	down_write(&interfaces_sem);
-	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
-		if (ipmi_interfaces[i] == NULL) {
-			new_intf->intf_num = i;
-			new_intf->version_major = version_major;
-			new_intf->version_minor = version_minor;
+	memset(intf, 0, sizeof(*intf));
+	intf->intf_num = -1;
+	kref_init(&intf->refcount);
+	intf->version_major = version_major;
+	intf->version_minor = version_minor;
 	for (j = 0; j < IPMI_MAX_CHANNELS; j++) {
-				new_intf->channels[j].address
-					= IPMI_BMC_SLAVE_ADDR;
-				new_intf->channels[j].lun = 2;
+		intf->channels[j].address = IPMI_BMC_SLAVE_ADDR;
+		intf->channels[j].lun = 2;
 	}
 	if (slave_addr != 0)
-				new_intf->channels[0].address = slave_addr;
-			rwlock_init(&(new_intf->users_lock));
-			INIT_LIST_HEAD(&(new_intf->users));
-			new_intf->handlers = handlers;
-			new_intf->send_info = send_info;
-			spin_lock_init(&(new_intf->seq_lock));
+		intf->channels[0].address = slave_addr;
+	INIT_LIST_HEAD(&intf->users);
+	intf->handlers = handlers;
+	intf->send_info = send_info;
+	spin_lock_init(&intf->seq_lock);
 	for (j = 0; j < IPMI_IPMB_NUM_SEQ; j++) {
-				new_intf->seq_table[j].inuse = 0;
-				new_intf->seq_table[j].seqid = 0;
+		intf->seq_table[j].inuse = 0;
+		intf->seq_table[j].seqid = 0;
 	}
-			new_intf->curr_seq = 0;
+	intf->curr_seq = 0;
 #ifdef CONFIG_PROC_FS
-			spin_lock_init(&(new_intf->proc_entry_lock));
+	spin_lock_init(&intf->proc_entry_lock);
 #endif
-			spin_lock_init(&(new_intf->waiting_msgs_lock));
-			INIT_LIST_HEAD(&(new_intf->waiting_msgs));
-			spin_lock_init(&(new_intf->events_lock));
-			INIT_LIST_HEAD(&(new_intf->waiting_events));
-			new_intf->waiting_events_count = 0;
-			rwlock_init(&(new_intf->cmd_rcvr_lock));
-			init_waitqueue_head(&new_intf->waitq);
-			INIT_LIST_HEAD(&(new_intf->cmd_rcvrs));
-
-			spin_lock_init(&(new_intf->counter_lock));
+	spin_lock_init(&intf->waiting_msgs_lock);
+	INIT_LIST_HEAD(&intf->waiting_msgs);
+	spin_lock_init(&intf->events_lock);
+	INIT_LIST_HEAD(&intf->waiting_events);
+	intf->waiting_events_count = 0;
+	spin_lock_init(&intf->cmd_rcvrs_lock);
+	INIT_LIST_HEAD(&intf->cmd_rcvrs);
+	init_waitqueue_head(&intf->waitq);
+
+	spin_lock_init(&intf->counter_lock);
+	intf->proc_dir = NULL;
 
+	rv = -ENOMEM;
 	spin_lock_irqsave(&interfaces_lock, flags);
-			ipmi_interfaces[i] = new_intf;
-			spin_unlock_irqrestore(&interfaces_lock, flags);
-
+	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
+		if (ipmi_interfaces[i] == NULL) {
+			intf->intf_num = i;
+			/* Reserve the entry till we are done. */
+			ipmi_interfaces[i] = IPMI_INVALID_INTERFACE_ENTRY;
 			rv = 0;
-			*intf = new_intf;
 			break;
 		}
 	}
+	spin_unlock_irqrestore(&interfaces_lock, flags);
+	if (rv)
+		goto out;
 
-	downgrade_write(&interfaces_sem);
-
-	if (rv == 0)
-		rv = add_proc_entries(*intf, i);
+	/* FIXME - this is an ugly kludge, this sets the intf for the
+	   caller before sending any messages with it. */
+	*new_intf = intf;
 
-	if (rv == 0) {
 	if ((version_major > 1)
 	    || ((version_major == 1) && (version_minor >= 5)))
 	{
 		/* Start scanning the channels to see what is
 		   available. */
-			(*intf)->null_user_handler = channel_handler;
-			(*intf)->curr_channel = 0;
-			rv = send_channel_info_cmd(*intf, 0);
+		intf->null_user_handler = channel_handler;
+		intf->curr_channel = 0;
+		rv = send_channel_info_cmd(intf, 0);
 		if (rv)
 			goto out;
 
 		/* Wait for the channel info to be read. */
-			up_read(&interfaces_sem);
-			wait_event((*intf)->waitq,
-				   ((*intf)->curr_channel>=IPMI_MAX_CHANNELS));
-			down_read(&interfaces_sem);
-
-			if (ipmi_interfaces[i] != new_intf)
-				/* Well, it went away.  Just return. */
-				goto out;
+		wait_event(intf->waitq,
+			   intf->curr_channel >= IPMI_MAX_CHANNELS);
 	} else {
 		/* Assume a single IPMB channel at zero. */
-			(*intf)->channels[0].medium = IPMI_CHANNEL_MEDIUM_IPMB;
-			(*intf)->channels[0].protocol
-				= IPMI_CHANNEL_PROTOCOL_IPMB;
+		intf->channels[0].medium = IPMI_CHANNEL_MEDIUM_IPMB;
+		intf->channels[0].protocol = IPMI_CHANNEL_PROTOCOL_IPMB;
 	}
 
-		/* Call all the watcher interfaces to tell
-		   them that a new interface is available. */
-		call_smi_watchers(i);
-	}
+	if (rv == 0)
+		rv = add_proc_entries(intf, i);
 
  out:
-	up_read(&interfaces_sem);
-
 	if (rv) {
-		if (new_intf->proc_dir)
-			remove_proc_entries(new_intf);
-		kfree(new_intf);
-	}
-
-	return rv;
-}
-
-static void free_recv_msg_list(struct list_head *q)
-{
-	struct ipmi_recv_msg *msg, *msg2;
-
-	list_for_each_entry_safe(msg, msg2, q, link) {
-		list_del(&msg->link);
-		ipmi_free_recv_msg(msg);
+		if (intf->proc_dir)
+			remove_proc_entries(intf);
+		kref_put(&intf->refcount, intf_free);
+		if (i < MAX_IPMI_INTERFACES) {
+			spin_lock_irqsave(&interfaces_lock, flags);
+			ipmi_interfaces[i] = NULL;
+			spin_unlock_irqrestore(&interfaces_lock, flags);
 		}
-}
-
-static void free_cmd_rcvr_list(struct list_head *q)
-{
-	struct cmd_rcvr  *rcvr, *rcvr2;
-
-	list_for_each_entry_safe(rcvr, rcvr2, q, link) {
-		list_del(&rcvr->link);
-		kfree(rcvr);
+	} else {
+		spin_lock_irqsave(&interfaces_lock, flags);
+		ipmi_interfaces[i] = intf;
+		spin_unlock_irqrestore(&interfaces_lock, flags);
+		call_smi_watchers(i);
 	}
-}
-
-static void clean_up_interface_data(ipmi_smi_t intf)
-{
-	int i;
-
-	free_recv_msg_list(&(intf->waiting_msgs));
-	free_recv_msg_list(&(intf->waiting_events));
-	free_cmd_rcvr_list(&(intf->cmd_rcvrs));
 
-	for (i = 0; i < IPMI_IPMB_NUM_SEQ; i++) {
-		if ((intf->seq_table[i].inuse)
-		    && (intf->seq_table[i].recv_msg))
-		{
-			ipmi_free_recv_msg(intf->seq_table[i].recv_msg);
-		}	
-	}
+	return rv;
 }
 
 int ipmi_unregister_smi(ipmi_smi_t intf)
 {
-	int                     rv = -ENODEV;
 	int                     i;
 	struct ipmi_smi_watcher *w;
 	unsigned long           flags;
 
-	down_write(&interfaces_sem);
-	if (list_empty(&(intf->users)))
-	{
+	spin_lock_irqsave(&interfaces_lock, flags);
 	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
 		if (ipmi_interfaces[i] == intf) {
-				remove_proc_entries(intf);
-				spin_lock_irqsave(&interfaces_lock, flags);
-				ipmi_interfaces[i] = NULL;
-				clean_up_interface_data(intf);
-				spin_unlock_irqrestore(&interfaces_lock,flags);
-				kfree(intf);
-				rv = 0;
-				goto out_call_watcher;
-			}
+			/* Set the interface number reserved until we
+			 * are done. */
+			ipmi_interfaces[i] = IPMI_INVALID_INTERFACE_ENTRY;
+			intf->intf_num = -1;
+			break;
 		}
-	} else {
-		rv = -EBUSY;
 	}
-	up_write(&interfaces_sem);
+	spin_unlock_irqrestore(&interfaces_lock,flags);
 
-	return rv;
+	if (i == MAX_IPMI_INTERFACES)
+		return -ENODEV;
 
- out_call_watcher:
-	downgrade_write(&interfaces_sem);
+	remove_proc_entries(intf);
 
 	/* Call all the watcher interfaces to tell them that
 	   an interface is gone. */
 	down_read(&smi_watchers_sem);
-	list_for_each_entry(w, &smi_watchers, link) {
+	list_for_each_entry(w, &smi_watchers, link)
 		w->smi_gone(i);
-	}
 	up_read(&smi_watchers_sem);
-	up_read(&interfaces_sem);
+
+	/* Allow the entry to be reused now. */
+	spin_lock_irqsave(&interfaces_lock, flags);
+	ipmi_interfaces[i] = NULL;
+	spin_unlock_irqrestore(&interfaces_lock,flags);
+
+	kref_put(&intf->refcount, intf_free);
 	return 0;
 }
 
@@ -2023,16 +2058,14 @@ static int handle_ipmb_get_msg_cmd(ipmi_smi_t          intf,
 	netfn = msg->rsp[4] >> 2;
 	cmd = msg->rsp[8];
 
-	read_lock(&(intf->cmd_rcvr_lock));
-	
-	/* Find the command/netfn. */
-	list_for_each_entry(rcvr, &(intf->cmd_rcvrs), link) {
-		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)) {
+	spin_lock_irqsave(&intf->cmd_rcvrs_lock, flags);
+	rcvr = find_cmd_rcvr(intf, netfn, cmd);
+	if (rcvr) {
 		user = rcvr->user;
-			break;
-		}
-	}
-	read_unlock(&(intf->cmd_rcvr_lock));
+		kref_get(&user->refcount);
+	} else
+		user = NULL;
+	spin_unlock_irqrestore(&intf->cmd_rcvrs_lock, flags);
 
 	if (user == NULL) {
 		/* We didn't find a user, deliver an error response. */
@@ -2079,6 +2112,7 @@ static int handle_ipmb_get_msg_cmd(ipmi_smi_t          intf,
                            message, so requeue it for handling
                            later. */
 			rv = 1;
+			kref_put(&user->refcount, free_user);
 		} else {
 			/* Extract the source address from the data. */
 			ipmb_addr = (struct ipmi_ipmb_addr *) &recv_msg->addr;
@@ -2204,19 +2238,17 @@ static int handle_lan_get_msg_cmd(ipmi_smi_t          intf,
 	netfn = msg->rsp[6] >> 2;
 	cmd = msg->rsp[10];
 
-	read_lock(&(intf->cmd_rcvr_lock));
-
-	/* Find the command/netfn. */
-	list_for_each_entry(rcvr, &(intf->cmd_rcvrs), link) {
-		if ((rcvr->netfn == netfn) && (rcvr->cmd == cmd)) {
+	spin_lock_irqsave(&intf->cmd_rcvrs_lock, flags);
+	rcvr = find_cmd_rcvr(intf, netfn, cmd);
+	if (rcvr) {
 		user = rcvr->user;
-			break;
-		}
-	}
-	read_unlock(&(intf->cmd_rcvr_lock));
+		kref_get(&user->refcount);
+	} else
+		user = NULL;
+	spin_unlock_irqrestore(&intf->cmd_rcvrs_lock, flags);
 
 	if (user == NULL) {
-		/* We didn't find a user, deliver an error response. */
+		/* We didn't find a user, just give up. */
 		spin_lock_irqsave(&intf->counter_lock, flags);
 		intf->unhandled_commands++;
 		spin_unlock_irqrestore(&intf->counter_lock, flags);
@@ -2235,6 +2267,7 @@ static int handle_lan_get_msg_cmd(ipmi_smi_t          intf,
                            message, so requeue it for handling
                            later. */
 			rv = 1;
+			kref_put(&user->refcount, free_user);
 		} else {
 			/* Extract the source address from the data. */
 			lan_addr = (struct ipmi_lan_addr *) &recv_msg->addr;
@@ -2286,8 +2319,6 @@ static void copy_event_into_recv_msg(struct ipmi_recv_msg *recv_msg,
 	recv_msg->msg.data_len = msg->rsp_size - 3;
 }
 
-/* This will be called with the intf->users_lock read-locked, so no need
-   to do that here. */
 static int handle_read_event_rsp(ipmi_smi_t          intf,
 				 struct ipmi_smi_msg *msg)
 {
@@ -2313,7 +2344,7 @@ static int handle_read_event_rsp(ipmi_smi_t          intf,
 
 	INIT_LIST_HEAD(&msgs);
 
-	spin_lock_irqsave(&(intf->events_lock), flags);
+	spin_lock_irqsave(&intf->events_lock, flags);
 
 	spin_lock(&intf->counter_lock);
 	intf->events++;
@@ -2321,12 +2352,14 @@ static int handle_read_event_rsp(ipmi_smi_t          intf,
 
 	/* Allocate and fill in one message for every user that is getting
 	   events. */
-	list_for_each_entry(user, &(intf->users), link) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(user, &intf->users, link) {
 		if (! user->gets_events)
 			continue;
 
 		recv_msg = ipmi_alloc_recv_msg();
 		if (! recv_msg) {
+			rcu_read_unlock();
 			list_for_each_entry_safe(recv_msg, recv_msg2, &msgs, link) {
 				list_del(&recv_msg->link);
 				ipmi_free_recv_msg(recv_msg);
@@ -2342,8 +2375,10 @@ static int handle_read_event_rsp(ipmi_smi_t          intf,
 
 		copy_event_into_recv_msg(recv_msg, msg);
 		recv_msg->user = user;
+		kref_get(&user->refcount);
 		list_add_tail(&(recv_msg->link), &msgs);
 	}
+	rcu_read_unlock();
 
 	if (deliver_count) {
 		/* Now deliver all the messages. */
@@ -2382,9 +2417,8 @@ static int handle_bmc_rsp(ipmi_smi_t          intf,
 			  struct ipmi_smi_msg *msg)
 {
 	struct ipmi_recv_msg *recv_msg;
-	int                  found = 0;
-	struct ipmi_user     *user;
 	unsigned long        flags;
+	struct ipmi_user     *user;
 
 	recv_msg = (struct ipmi_recv_msg *) msg->user_data;
 	if (recv_msg == NULL)
@@ -2396,16 +2430,9 @@ static int handle_bmc_rsp(ipmi_smi_t          intf,
 		return 0;
 	}
 
+	user = recv_msg->user;
 	/* Make sure the user still exists. */
-	list_for_each_entry(user, &(intf->users), link) {
-		if (user == recv_msg->user) {
-			/* Found it, so we can deliver it */
-			found = 1;
-			break;
-		}
-	}
-
-	if ((! found) && recv_msg->user) {
+	if (user && !user->valid) {
 		/* The user for the message went away, so give up. */
 		spin_lock_irqsave(&intf->counter_lock, flags);
 		intf->unhandled_local_responses++;
@@ -2498,13 +2525,18 @@ static int handle_new_recv_msg(ipmi_smi_t          intf,
 			/* Invalid channel number */
 			goto out;
 
-		if (recv_msg) {
+		if (!recv_msg)
+			goto out;
+
+		/* Make sure the user still exists. */
+		if (!recv_msg->user || !recv_msg->user->valid)
+			goto out;
+
 		recv_msg->recv_type = IPMI_RESPONSE_RESPONSE_TYPE;
 		recv_msg->msg.data = recv_msg->msg_data;
 		recv_msg->msg.data_len = 1;
 		recv_msg->msg_data[0] = msg->rsp[2];
 		deliver_response(recv_msg);
-		}
 	} else if ((msg->rsp[0] == ((IPMI_NETFN_APP_REQUEST|1) << 2))
 		   && (msg->rsp[1] == IPMI_GET_MSG_CMD))
 	{
@@ -2570,14 +2602,11 @@ void ipmi_smi_msg_received(ipmi_smi_t          intf,
 	int           rv;
 
 
-	/* Lock the user lock so the user can't go away while we are
-	   working on it. */
-	read_lock(&(intf->users_lock));
-
 	if ((msg->data_size >= 2)
 	    && (msg->data[0] == (IPMI_NETFN_APP_REQUEST << 2))
 	    && (msg->data[1] == IPMI_SEND_MSG_CMD)
-	    && (msg->user_data == NULL)) {
+	    && (msg->user_data == NULL))
+	{
 		/* This is the local response to a command send, start
                    the timer for these.  The user_data will not be
                    NULL if this is a response send, and we will let
@@ -2612,46 +2641,46 @@ void ipmi_smi_msg_received(ipmi_smi_t          intf,
 		}
 
 		ipmi_free_smi_msg(msg);
-		goto out_unlock;
+		goto out;
 	}
 
 	/* To preserve message order, if the list is not empty, we
            tack this message onto the end of the list. */
-	spin_lock_irqsave(&(intf->waiting_msgs_lock), flags);
-	if (!list_empty(&(intf->waiting_msgs))) {
-		list_add_tail(&(msg->link), &(intf->waiting_msgs));
-		spin_unlock_irqrestore(&(intf->waiting_msgs_lock), flags);
-		goto out_unlock;
+	spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+	if (!list_empty(&intf->waiting_msgs)) {
+		list_add_tail(&msg->link, &intf->waiting_msgs);
+		spin_unlock(&intf->waiting_msgs_lock);
+		goto out;
 	}
-	spin_unlock_irqrestore(&(intf->waiting_msgs_lock), flags);
+	spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
 		
 	rv = handle_new_recv_msg(intf, msg);
 	if (rv > 0) {
 		/* Could not handle the message now, just add it to a
                    list to handle later. */
-		spin_lock_irqsave(&(intf->waiting_msgs_lock), flags);
-		list_add_tail(&(msg->link), &(intf->waiting_msgs));
-		spin_unlock_irqrestore(&(intf->waiting_msgs_lock), flags);
+		spin_lock(&intf->waiting_msgs_lock);
+		list_add_tail(&msg->link, &intf->waiting_msgs);
+		spin_unlock(&intf->waiting_msgs_lock);
 	} else if (rv == 0) {
 		ipmi_free_smi_msg(msg);
 	}
 
- out_unlock:
-	read_unlock(&(intf->users_lock));
+ out:
+	return;
 }
 
 void ipmi_smi_watchdog_pretimeout(ipmi_smi_t intf)
 {
 	ipmi_user_t user;
 
-	read_lock(&(intf->users_lock));
-	list_for_each_entry(user, &(intf->users), link) {
+	rcu_read_lock();
+	list_for_each_entry_rcu(user, &intf->users, link) {
 		if (! user->handler->ipmi_watchdog_pretimeout)
 			continue;
 
 		user->handler->ipmi_watchdog_pretimeout(user->handler_data);
 	}
-	read_unlock(&(intf->users_lock));
+	rcu_read_unlock();
 }
 
 static void
@@ -2691,63 +2720,28 @@ smi_from_recv_msg(ipmi_smi_t intf, struct ipmi_recv_msg *recv_msg,
 	return smi_msg;
 }
 
-static void
-ipmi_timeout_handler(long timeout_period)
+static void check_msg_timeout(ipmi_smi_t intf, struct seq_table *ent,
+			      struct list_head *timeouts, long timeout_period,
+			      int slot, unsigned long *flags)
 {
-	ipmi_smi_t           intf;
-	struct list_head     timeouts;
-	struct ipmi_recv_msg *msg, *msg2;
-	struct ipmi_smi_msg  *smi_msg, *smi_msg2;
-	unsigned long        flags;
-	int                  i, j;
-
-	INIT_LIST_HEAD(&timeouts);
-
-	spin_lock(&interfaces_lock);
-	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
-		intf = ipmi_interfaces[i];
-		if (intf == NULL)
-			continue;
-
-		read_lock(&(intf->users_lock));
-
-		/* See if any waiting messages need to be processed. */
-		spin_lock_irqsave(&(intf->waiting_msgs_lock), flags);
-		list_for_each_entry_safe(smi_msg, smi_msg2, &(intf->waiting_msgs), link) {
-			if (! handle_new_recv_msg(intf, smi_msg)) {
-				list_del(&smi_msg->link);
-				ipmi_free_smi_msg(smi_msg);
-			} else {
-				/* To preserve message order, quit if we
-				   can't handle a message. */
-				break;
-			}
-		}
-		spin_unlock_irqrestore(&(intf->waiting_msgs_lock), flags);
+	struct ipmi_recv_msg *msg;
 
-		/* Go through the seq table and find any messages that
-		   have timed out, putting them in the timeouts
-		   list. */
-		spin_lock_irqsave(&(intf->seq_lock), flags);
-		for (j = 0; j < IPMI_IPMB_NUM_SEQ; j++) {
-			struct seq_table *ent = &(intf->seq_table[j]);
 	if (!ent->inuse)
-				continue;
+		return;
 
 	ent->timeout -= timeout_period;
 	if (ent->timeout > 0)
-				continue;
+		return;
 
 	if (ent->retries_left == 0) {
 		/* The message has used all its retries. */
 		ent->inuse = 0;
 		msg = ent->recv_msg;
-				list_add_tail(&(msg->link), &timeouts);
+		list_add_tail(&msg->link, timeouts);
 		spin_lock(&intf->counter_lock);
 		if (ent->broadcast)
 			intf->timed_out_ipmb_broadcasts++;
-				else if (ent->recv_msg->addr.addr_type
-					 == IPMI_LAN_ADDR_TYPE)
+		else if (ent->recv_msg->addr.addr_type == IPMI_LAN_ADDR_TYPE)
 			intf->timed_out_lan_commands++;
 		else
 			intf->timed_out_ipmb_commands++;
@@ -2761,18 +2755,18 @@ ipmi_timeout_handler(long timeout_period)
 		ent->timeout = MAX_MSG_TIMEOUT;
 		ent->retries_left--;
 		spin_lock(&intf->counter_lock);
-				if (ent->recv_msg->addr.addr_type
-				    == IPMI_LAN_ADDR_TYPE)
+		if (ent->recv_msg->addr.addr_type == IPMI_LAN_ADDR_TYPE)
 			intf->retransmitted_lan_commands++;
 		else
 			intf->retransmitted_ipmb_commands++;
 		spin_unlock(&intf->counter_lock);
-				smi_msg = smi_from_recv_msg(intf,
-						ent->recv_msg, j, ent->seqid);
+
+		smi_msg = smi_from_recv_msg(intf, ent->recv_msg, slot,
+					    ent->seqid);
 		if (! smi_msg)
-					continue;
+			return;
 
-				spin_unlock_irqrestore(&(intf->seq_lock),flags);
+		spin_unlock_irqrestore(&intf->seq_lock, *flags);
 		/* Send the new message.  We send with a zero
 		 * priority.  It timed out, I doubt time is
 		 * that critical now, and high priority
@@ -2780,16 +2774,58 @@ ipmi_timeout_handler(long timeout_period)
 		 * local MC, which don't get resent. */
 		intf->handlers->sender(intf->send_info,
 				       smi_msg, 0);
-				spin_lock_irqsave(&(intf->seq_lock), flags);
+		spin_lock_irqsave(&intf->seq_lock, *flags);
 	}
+}
+
+static void ipmi_timeout_handler(long timeout_period)
+{
+	ipmi_smi_t           intf;
+	struct list_head     timeouts;
+	struct ipmi_recv_msg *msg, *msg2;
+	struct ipmi_smi_msg  *smi_msg, *smi_msg2;
+	unsigned long        flags;
+	int                  i, j;
+
+	INIT_LIST_HEAD(&timeouts);
+
+	spin_lock(&interfaces_lock);
+	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
+		intf = ipmi_interfaces[i];
+		if (IPMI_INVALID_INTERFACE(intf))
+			continue;
+		kref_get(&intf->refcount);
+		spin_unlock(&interfaces_lock);
+
+		/* See if any waiting messages need to be processed. */
+		spin_lock_irqsave(&intf->waiting_msgs_lock, flags);
+		list_for_each_entry_safe(smi_msg, smi_msg2, &intf->waiting_msgs, link) {
+			if (! handle_new_recv_msg(intf, smi_msg)) {
+				list_del(&smi_msg->link);
+				ipmi_free_smi_msg(smi_msg);
+			} else {
+				/* To preserve message order, quit if we
+				   can't handle a message. */
+				break;
 			}
-		spin_unlock_irqrestore(&(intf->seq_lock), flags);
+		}
+		spin_unlock_irqrestore(&intf->waiting_msgs_lock, flags);
 
-		list_for_each_entry_safe(msg, msg2, &timeouts, link) {
+		/* Go through the seq table and find any messages that
+		   have timed out, putting them in the timeouts
+		   list. */
+		spin_lock_irqsave(&intf->seq_lock, flags);
+		for (j = 0; j < IPMI_IPMB_NUM_SEQ; j++)
+			check_msg_timeout(intf, &(intf->seq_table[j]),
+					  &timeouts, timeout_period, j,
+					  &flags);
+		spin_unlock_irqrestore(&intf->seq_lock, flags);
+
+		list_for_each_entry_safe(msg, msg2, &timeouts, link)
 			handle_msg_timeout(msg);
-		}
 
-		read_unlock(&(intf->users_lock));
+		kref_put(&intf->refcount, intf_free);
+		spin_lock(&interfaces_lock);
 	}
 	spin_unlock(&interfaces_lock);
 }
@@ -2802,7 +2838,7 @@ static void ipmi_request_event(void)
 	spin_lock(&interfaces_lock);
 	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
 		intf = ipmi_interfaces[i];
-		if (intf == NULL)
+		if (IPMI_INVALID_INTERFACE(intf))
 			continue;
 
 		intf->handlers->request_events(intf->send_info);
@@ -2884,6 +2920,13 @@ struct ipmi_recv_msg *ipmi_alloc_recv_msg(void)
 	return rv;
 }
 
+void ipmi_free_recv_msg(struct ipmi_recv_msg *msg)
+{
+	if (msg->user)
+		kref_put(&msg->user->refcount, free_user);
+	msg->done(msg);
+}
+
 #ifdef CONFIG_IPMI_PANIC_EVENT
 
 static void dummy_smi_done_handler(struct ipmi_smi_msg *msg)
@@ -2964,7 +3007,7 @@ static void send_panic_events(char *str)
 	/* For every registered interface, send the event. */
 	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
 		intf = ipmi_interfaces[i];
-		if (intf == NULL)
+		if (IPMI_INVALID_INTERFACE(intf))
 			continue;
 
 		/* Send the event announcing the panic. */
@@ -2995,7 +3038,7 @@ static void send_panic_events(char *str)
 		int                   j;
 
 		intf = ipmi_interfaces[i];
-		if (intf == NULL)
+		if (IPMI_INVALID_INTERFACE(intf))
 			continue;
 
 		/* First job here is to figure out where to send the
@@ -3131,7 +3174,7 @@ static int panic_event(struct notifier_block *this,
 	/* For every registered interface, set it to run to completion. */
 	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
 		intf = ipmi_interfaces[i];
-		if (intf == NULL)
+		if (IPMI_INVALID_INTERFACE(intf))
 			continue;
 
 		intf->handlers->set_run_to_completion(intf->send_info, 1);
@@ -3160,9 +3203,8 @@ static int ipmi_init_msghandler(void)
 	printk(KERN_INFO "ipmi message handler version "
 	       IPMI_DRIVER_VERSION "\n");
 
-	for (i = 0; i < MAX_IPMI_INTERFACES; i++) {
+	for (i = 0; i < MAX_IPMI_INTERFACES; i++)
 		ipmi_interfaces[i] = NULL;
-	}
 
 #ifdef CONFIG_PROC_FS
 	proc_ipmi_root = proc_mkdir("ipmi", NULL);
@@ -3258,3 +3300,4 @@ EXPORT_SYMBOL(ipmi_get_my_LUN);
 EXPORT_SYMBOL(ipmi_smi_add_proc_entry);
 EXPORT_SYMBOL(proc_ipmi_root);
 EXPORT_SYMBOL(ipmi_user_set_run_to_completion);
+EXPORT_SYMBOL(ipmi_free_recv_msg);

include/linux/ipmi.h

@@ -256,10 +256,7 @@ struct ipmi_recv_msg
 };
 
 /* Allocate and free the receive message. */
-static inline void ipmi_free_recv_msg(struct ipmi_recv_msg *msg)
-{
-	msg->done(msg);
-}
+void ipmi_free_recv_msg(struct ipmi_recv_msg *msg);
 
 struct ipmi_user_hndl
 {