Drivers: hv: rename sc_lock to the more generic lock

sc_lock spinlock in struct vmbus_channel is being used to not only protect the
sc_list field, e.g. vmbus_open() function uses it to implement test-and-set
access to the state field. Rename it to the more generic 'lock' and add the
description.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel.c

@@ -73,14 +73,14 @@ int vmbus_open(struct vmbus_channel *newchannel, u32 send_ringbuffer_size,
 	unsigned long flags;
 	int ret, t, err = 0;
 
-	spin_lock_irqsave(&newchannel->sc_lock, flags);
+	spin_lock_irqsave(&newchannel->lock, flags);
 	if (newchannel->state == CHANNEL_OPEN_STATE) {
 		newchannel->state = CHANNEL_OPENING_STATE;
 	} else {
-		spin_unlock_irqrestore(&newchannel->sc_lock, flags);
+		spin_unlock_irqrestore(&newchannel->lock, flags);
 		return -EINVAL;
 	}
-	spin_unlock_irqrestore(&newchannel->sc_lock, flags);
+	spin_unlock_irqrestore(&newchannel->lock, flags);
 
 	newchannel->onchannel_callback = onchannelcallback;
 	newchannel->channel_callback_context = context;

drivers/hv/channel_mgmt.c

@@ -146,7 +146,7 @@ static struct vmbus_channel *alloc_channel(void)
 		return NULL;
 
 	spin_lock_init(&channel->inbound_lock);
-	spin_lock_init(&channel->sc_lock);
+	spin_lock_init(&channel->lock);
 
 	INIT_LIST_HEAD(&channel->sc_list);
 	INIT_LIST_HEAD(&channel->percpu_list);
@@ -246,9 +246,9 @@ static void vmbus_process_rescind_offer(struct work_struct *work)
 		spin_unlock_irqrestore(&vmbus_connection.channel_lock, flags);
 	} else {
 		primary_channel = channel->primary_channel;
-		spin_lock_irqsave(&primary_channel->sc_lock, flags);
+		spin_lock_irqsave(&primary_channel->lock, flags);
 		list_del(&channel->sc_list);
-		spin_unlock_irqrestore(&primary_channel->sc_lock, flags);
+		spin_unlock_irqrestore(&primary_channel->lock, flags);
 	}
 	free_channel(channel);
 }
@@ -323,9 +323,9 @@ static void vmbus_process_offer(struct work_struct *work)
 			 * Process the sub-channel.
 			 */
 			newchannel->primary_channel = channel;
-			spin_lock_irqsave(&channel->sc_lock, flags);
+			spin_lock_irqsave(&channel->lock, flags);
 			list_add_tail(&newchannel->sc_list, &channel->sc_list);
-			spin_unlock_irqrestore(&channel->sc_lock, flags);
+			spin_unlock_irqrestore(&channel->lock, flags);
 
 			if (newchannel->target_cpu != get_cpu()) {
 				put_cpu();

include/linux/hyperv.h

@@ -734,7 +734,12 @@ struct vmbus_channel {
 	 */
 	void (*sc_creation_callback)(struct vmbus_channel *new_sc);
 
-	spinlock_t sc_lock;
+	/*
+	 * The spinlock to protect the structure. It is being used to protect
+	 * test-and-set access to various attributes of the structure as well
+	 * as all sc_list operations.
+	 */
+	spinlock_t lock;
 	/*
 	 * All Sub-channels of a primary channel are linked here.
 	 */