ipmi: Make the smi watcher be disabled immediately when not needed

The code to tell the lower layer to enable or disable watching for
certain things was lazy in disabling, it waited until a timer tick
to see if a disable was necessary.  Not a really big deal, but it
could be improved.

Modify the code to enable and disable watching immediately and don't
do it from the background timer any more.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Tested-by: Kamlakant Patel <kamlakant.patel@cavium.com>

1 files changed, 90 insertions, 74 deletions

diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
index 2e008efa735f..5bc84fbbeee5 100644
--- a/drivers/char/ipmi/ipmi_msghandler.c
+++ b/drivers/char/ipmi/ipmi_msghandler.c
@@ -534,15 +534,20 @@ struct ipmi_smi {
 	atomic_t         event_waiters;
 	unsigned int     ticks_to_req_ev;
 
+	spinlock_t       watch_lock; /* For dealing with watch stuff below. */
+
 	/* How many users are waiting for commands? */
-	atomic_t         command_waiters;
+	unsigned int     command_waiters;
 
 	/* How many users are waiting for watchdogs? */
-	atomic_t         watchdog_waiters;
+	unsigned int     watchdog_waiters;
+
+	/* How many users are waiting for message responses? */
+	unsigned int     response_waiters;
 
 	/*
 	 * Tells what the lower layer has last been asked to watch for,
-	 * messages and/or watchdogs.  Protected by xmit_msgs_lock.
+	 * messages and/or watchdogs.  Protected by watch_lock.
 	 */
 	unsigned int     last_watch_mask;
 
@@ -938,6 +943,64 @@ static void deliver_err_response(struct ipmi_smi *intf,
 	deliver_local_response(intf, msg);
 }
 
+static void smi_add_watch(struct ipmi_smi *intf, unsigned int flags)
+{
+	unsigned long iflags;
+
+	if (!intf->handlers->set_need_watch)
+		return;
+
+	spin_lock_irqsave(&intf->watch_lock, iflags);
+	if (flags & IPMI_WATCH_MASK_CHECK_MESSAGES)
+		intf->response_waiters++;
+
+	if (flags & IPMI_WATCH_MASK_CHECK_WATCHDOG)
+		intf->watchdog_waiters++;
+
+	if (flags & IPMI_WATCH_MASK_CHECK_COMMANDS)
+		intf->command_waiters++;
+
+	if ((intf->last_watch_mask & flags) != flags) {
+		intf->last_watch_mask |= flags;
+		intf->handlers->set_need_watch(intf->send_info,
+					       intf->last_watch_mask);
+	}
+	spin_unlock_irqrestore(&intf->watch_lock, iflags);
+}
+
+static void smi_remove_watch(struct ipmi_smi *intf, unsigned int flags)
+{
+	unsigned long iflags;
+
+	if (!intf->handlers->set_need_watch)
+		return;
+
+	spin_lock_irqsave(&intf->watch_lock, iflags);
+	if (flags & IPMI_WATCH_MASK_CHECK_MESSAGES)
+		intf->response_waiters--;
+
+	if (flags & IPMI_WATCH_MASK_CHECK_WATCHDOG)
+		intf->watchdog_waiters--;
+
+	if (flags & IPMI_WATCH_MASK_CHECK_COMMANDS)
+		intf->command_waiters--;
+
+	flags = 0;
+	if (intf->response_waiters)
+		flags |= IPMI_WATCH_MASK_CHECK_MESSAGES;
+	if (intf->watchdog_waiters)
+		flags |= IPMI_WATCH_MASK_CHECK_WATCHDOG;
+	if (intf->command_waiters)
+		flags |= IPMI_WATCH_MASK_CHECK_COMMANDS;
+
+	if (intf->last_watch_mask != flags) {
+		intf->last_watch_mask = flags;
+		intf->handlers->set_need_watch(intf->send_info,
+					       intf->last_watch_mask);
+	}
+	spin_unlock_irqrestore(&intf->watch_lock, iflags);
+}
+
 /*
  * Find the next sequence number not being used and add the given
  * message with the given timeout to the sequence table.  This must be
@@ -981,6 +1044,7 @@ static int intf_next_seq(struct ipmi_smi      *intf,
 		*seq = i;
 		*seqid = intf->seq_table[i].seqid;
 		intf->curr_seq = (i+1)%IPMI_IPMB_NUM_SEQ;
+		smi_add_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES);
 		need_waiter(intf);
 	} else {
 		rv = -EAGAIN;
@@ -1019,6 +1083,7 @@ static int intf_find_seq(struct ipmi_smi      *intf,
 				&& (ipmi_addr_equal(addr, &msg->addr))) {
 			*recv_msg = msg;
 			intf->seq_table[seq].inuse = 0;
+			smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES);
 			rv = 0;
 		}
 	}
@@ -1080,6 +1145,7 @@ static int intf_err_seq(struct ipmi_smi *intf,
 		struct seq_table *ent = &intf->seq_table[seq];
 
 		ent->inuse = 0;
+		smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES);
 		msg = ent->recv_msg;
 		rv = 0;
 	}
@@ -1091,30 +1157,6 @@ static int intf_err_seq(struct ipmi_smi *intf,
 	return rv;
 }
 
-/* Must be called with xmit_msgs_lock held. */
-static void smi_tell_to_watch(struct ipmi_smi *intf,
-			      unsigned int flags,
-			      struct ipmi_smi_msg *smi_msg)
-{
-	if (flags & IPMI_WATCH_MASK_CHECK_MESSAGES) {
-		if (!smi_msg)
-			return;
-
-		if (!smi_msg->needs_response)
-			return;
-	}
-
-	if (!intf->handlers->set_need_watch)
-		return;
-
-	if ((intf->last_watch_mask & flags) == flags)
-		return;
-
-	intf->last_watch_mask |= flags;
-	intf->handlers->set_need_watch(intf->send_info,
-				       intf->last_watch_mask);
-}
-
 int ipmi_create_user(unsigned int          if_num,
 		     const struct ipmi_user_hndl *handler,
 		     void                  *handler_data,
@@ -1175,12 +1217,9 @@ int ipmi_create_user(unsigned int          if_num,
 	spin_lock_irqsave(&intf->seq_lock, flags);
 	list_add_rcu(&new_user->link, &intf->users);
 	spin_unlock_irqrestore(&intf->seq_lock, flags);
-	if (handler->ipmi_watchdog_pretimeout) {
+	if (handler->ipmi_watchdog_pretimeout)
 		/* User wants pretimeouts, so make sure to watch for them. */
-		if (atomic_inc_return(&intf->watchdog_waiters) == 1)
-			smi_tell_to_watch(intf, IPMI_WATCH_MASK_CHECK_WATCHDOG,
-					  NULL);
-	}
+		smi_add_watch(intf, IPMI_WATCH_MASK_CHECK_WATCHDOG);
 	srcu_read_unlock(&ipmi_interfaces_srcu, index);
 	*user = new_user;
 	return 0;
@@ -1251,7 +1290,7 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
 		user->handler->shutdown(user->handler_data);
 
 	if (user->handler->ipmi_watchdog_pretimeout)
-		atomic_dec(&intf->watchdog_waiters);
+		smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_WATCHDOG);
 
 	if (user->gets_events)
 		atomic_dec(&intf->event_waiters);
@@ -1264,6 +1303,7 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
 		if (intf->seq_table[i].inuse
 		    && (intf->seq_table[i].recv_msg->user == user)) {
 			intf->seq_table[i].inuse = 0;
+			smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES);
 			ipmi_free_recv_msg(intf->seq_table[i].recv_msg);
 		}
 	}
@@ -1606,8 +1646,7 @@ int ipmi_register_for_cmd(struct ipmi_user *user,
 		goto out_unlock;
 	}
 
-	if (atomic_inc_return(&intf->command_waiters) == 1)
-		smi_tell_to_watch(intf, IPMI_WATCH_MASK_CHECK_COMMANDS, NULL);
+	smi_add_watch(intf, IPMI_WATCH_MASK_CHECK_COMMANDS);
 
 	list_add_rcu(&rcvr->link, &intf->cmd_rcvrs);
 
@@ -1657,7 +1696,7 @@ int ipmi_unregister_for_cmd(struct ipmi_user *user,
 	synchronize_rcu();
 	release_ipmi_user(user, index);
 	while (rcvrs) {
-		atomic_dec(&intf->command_waiters);
+		smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_COMMANDS);
 		rcvr = rcvrs;
 		rcvrs = rcvr->next;
 		kfree(rcvr);
@@ -1785,8 +1824,6 @@ static void smi_send(struct ipmi_smi *intf,
 		spin_lock_irqsave(&intf->xmit_msgs_lock, flags);
 	smi_msg = smi_add_send_msg(intf, smi_msg, priority);
 
-	smi_tell_to_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES, smi_msg);
-
 	if (!run_to_completion)
 		spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
 
@@ -1986,9 +2023,6 @@ static int i_ipmi_req_ipmb(struct ipmi_smi        *intf,
 				ipmb_seq, broadcast,
 				source_address, source_lun);
 
-		/* We will be getting a response in the BMC message queue. */
-		smi_msg->needs_response = true;
-
 		/*
 		 * Copy the message into the recv message data, so we
 		 * can retransmit it later if necessary.
@@ -2176,7 +2210,6 @@ static int i_ipmi_request(struct ipmi_user     *user,
 			goto out;
 		}
 	}
-	smi_msg->needs_response = false;
 
 	rcu_read_lock();
 	if (intf->in_shutdown) {
@@ -3390,9 +3423,8 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
 	INIT_LIST_HEAD(&intf->xmit_msgs);
 	INIT_LIST_HEAD(&intf->hp_xmit_msgs);
 	spin_lock_init(&intf->events_lock);
+	spin_lock_init(&intf->watch_lock);
 	atomic_set(&intf->event_waiters, 0);
-	atomic_set(&intf->watchdog_waiters, 0);
-	atomic_set(&intf->command_waiters, 0);
 	intf->ticks_to_req_ev = IPMI_REQUEST_EV_TIME;
 	INIT_LIST_HEAD(&intf->waiting_events);
 	intf->waiting_events_count = 0;
@@ -4408,8 +4440,6 @@ static void smi_recv_tasklet(unsigned long val)
 		}
 	}
 
-	smi_tell_to_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES, newmsg);
-
 	if (!run_to_completion)
 		spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
 	if (newmsg)
@@ -4537,7 +4567,7 @@ static void check_msg_timeout(struct ipmi_smi *intf, struct seq_table *ent,
 			      struct list_head *timeouts,
 			      unsigned long timeout_period,
 			      int slot, unsigned long *flags,
-			      unsigned int *watch_mask)
+			      bool *need_timer)
 {
 	struct ipmi_recv_msg *msg;
 
@@ -4549,13 +4579,14 @@ static void check_msg_timeout(struct ipmi_smi *intf, struct seq_table *ent,
 
 	if (timeout_period < ent->timeout) {
 		ent->timeout -= timeout_period;
-		*watch_mask |= IPMI_WATCH_MASK_CHECK_MESSAGES;
+		*need_timer = true;
 		return;
 	}
 
 	if (ent->retries_left == 0) {
 		/* The message has used all its retries. */
 		ent->inuse = 0;
+		smi_remove_watch(intf, IPMI_WATCH_MASK_CHECK_MESSAGES);
 		msg = ent->recv_msg;
 		list_add_tail(&msg->link, timeouts);
 		if (ent->broadcast)
@@ -4568,7 +4599,7 @@ static void check_msg_timeout(struct ipmi_smi *intf, struct seq_table *ent,
 		struct ipmi_smi_msg *smi_msg;
 		/* More retries, send again. */
 
-		*watch_mask |= IPMI_WATCH_MASK_CHECK_MESSAGES;
+		*need_timer = true;
 
 		/*
 		 * Start with the max timer, set to normal timer after
@@ -4613,20 +4644,20 @@ static void check_msg_timeout(struct ipmi_smi *intf, struct seq_table *ent,
 	}
 }
 
-static unsigned int ipmi_timeout_handler(struct ipmi_smi *intf,
-					 unsigned long timeout_period)
+static bool ipmi_timeout_handler(struct ipmi_smi *intf,
+				 unsigned long timeout_period)
 {
 	struct list_head     timeouts;
 	struct ipmi_recv_msg *msg, *msg2;
 	unsigned long        flags;
 	int                  i;
-	unsigned int         watch_mask = 0;
+	bool                 need_timer = false;
 
 	if (!intf->bmc_registered) {
 		kref_get(&intf->refcount);
 		if (!schedule_work(&intf->bmc_reg_work)) {
 			kref_put(&intf->refcount, intf_free);
-			watch_mask |= IPMI_WATCH_MASK_INTERNAL;
+			need_timer = true;
 		}
 	}
 
@@ -4646,7 +4677,7 @@ static unsigned int ipmi_timeout_handler(struct ipmi_smi *intf,
 	for (i = 0; i < IPMI_IPMB_NUM_SEQ; i++)
 		check_msg_timeout(intf, &intf->seq_table[i],
 				  &timeouts, timeout_period, i,
-				  &flags, &watch_mask);
+				  &flags, &need_timer);
 	spin_unlock_irqrestore(&intf->seq_lock, flags);
 
 	list_for_each_entry_safe(msg, msg2, &timeouts, link)
@@ -4677,7 +4708,7 @@ static unsigned int ipmi_timeout_handler(struct ipmi_smi *intf,
 
 	tasklet_schedule(&intf->recv_tasklet);
 
-	return watch_mask;
+	return need_timer;
 }
 
 static void ipmi_request_event(struct ipmi_smi *intf)
@@ -4697,9 +4728,8 @@ static atomic_t stop_operation;
 static void ipmi_timeout(struct timer_list *unused)
 {
 	struct ipmi_smi *intf;
-	unsigned int watch_mask = 0;
+	bool need_timer = false;
 	int index;
-	unsigned long flags;
 
 	if (atomic_read(&stop_operation))
 		return;
@@ -4712,28 +4742,14 @@ static void ipmi_timeout(struct timer_list *unused)
 				ipmi_request_event(intf);
 				intf->ticks_to_req_ev = IPMI_REQUEST_EV_TIME;
 			}
-			watch_mask |= IPMI_WATCH_MASK_INTERNAL;
+			need_timer = true;
 		}
 
-		if (atomic_read(&intf->watchdog_waiters))
-			watch_mask |= IPMI_WATCH_MASK_CHECK_WATCHDOG;
-
-		if (atomic_read(&intf->command_waiters))
-			watch_mask |= IPMI_WATCH_MASK_CHECK_COMMANDS;
-
-		watch_mask |= ipmi_timeout_handler(intf, IPMI_TIMEOUT_TIME);
-
-		spin_lock_irqsave(&intf->xmit_msgs_lock, flags);
-		if (watch_mask != intf->last_watch_mask &&
-					intf->handlers->set_need_watch)
-			intf->handlers->set_need_watch(intf->send_info,
-						       watch_mask);
-		intf->last_watch_mask = watch_mask;
-		spin_unlock_irqrestore(&intf->xmit_msgs_lock, flags);
+		need_timer |= ipmi_timeout_handler(intf, IPMI_TIMEOUT_TIME);
 	}
 	srcu_read_unlock(&ipmi_interfaces_srcu, index);
 
-	if (watch_mask)
+	if (need_timer)
 		mod_timer(&ipmi_timer, jiffies + IPMI_TIMEOUT_JIFFIES);
 }