Drivers: hv: vmbus: Fix a rescind issue

The current rescind processing code will not correctly handle
the case where the host immediately rescinds a channel that has
been offerred. In this case, we could be blocked in the open call and
since the channel is rescinded, the host will not respond and we could
be blocked forever in the vmbus open call.i Fix this problem.

Signed-off-by: K. Y. Srinivasan <[e-mail]>
Cc: [e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/hv/channel.c

···
 		 */
 		return;
 	}
-	mutex_lock(&vmbus_connection.channel_mutex);
 	/*
 	 * Close all the sub-channels first and then close the
 	 * primary channel.
 	 */
 	list_for_each_safe(cur, tmp, &channel->sc_list) {
 		cur_channel = list_entry(cur, struct vmbus_channel, sc_list);
-		vmbus_close_internal(cur_channel);
 		if (cur_channel->rescind) {
+			wait_for_completion(&cur_channel->rescind_event);
+			mutex_lock(&vmbus_connection.channel_mutex);
+			vmbus_close_internal(cur_channel);
 			hv_process_channel_removal(
 					   cur_channel->offermsg.child_relid);
+		} else {
+			mutex_lock(&vmbus_connection.channel_mutex);
+			vmbus_close_internal(cur_channel);
 		}
+		mutex_unlock(&vmbus_connection.channel_mutex);
 	}
 	/*
 	 * Now close the primary.
 	 */
+	mutex_lock(&vmbus_connection.channel_mutex);
 	vmbus_close_internal(channel);
 	mutex_unlock(&vmbus_connection.channel_mutex);
 }

drivers/hv/channel_mgmt.c

···
 		return NULL;
 
 	spin_lock_init(&channel->lock);
+	init_completion(&channel->rescind_event);
 
 	INIT_LIST_HEAD(&channel->sc_list);
 	INIT_LIST_HEAD(&channel->percpu_list);
···
 	/*
 	 * Now wait for offer handling to complete.
 	 */
+	vmbus_rescind_cleanup(channel);
 	while (READ_ONCE(channel->probe_done) == false) {
 		/*
 		 * We wait here until any channel offer is currently
···
 	if (channel->device_obj) {
 		if (channel->chn_rescind_callback) {
 			channel->chn_rescind_callback(channel);
-			vmbus_rescind_cleanup(channel);
 			return;
 		}
 		/*
···
 		 */
 		dev = get_device(&channel->device_obj->device);
 		if (dev) {
-			vmbus_rescind_cleanup(channel);
 			vmbus_device_unregister(channel->device_obj);
 			put_device(dev);
 		}
···
 		 * 2. Then close the primary channel.
 		 */
 		mutex_lock(&vmbus_connection.channel_mutex);
-		vmbus_rescind_cleanup(channel);
 		if (channel->state == CHANNEL_OPEN_STATE) {
 			/*
 			 * The channel is currently not open;
 			 * it is safe for us to cleanup the channel.
 			 */
 			hv_process_channel_removal(rescind->child_relid);
+		} else {
+			complete(&channel->rescind_event);
 		}
 		mutex_unlock(&vmbus_connection.channel_mutex);
 	}

include/linux/hyperv.h

···
 	u8 monitor_bit;
 
 	bool rescind; /* got rescind msg */
+	struct completion rescind_event;
 
 	u32 ringbuffer_gpadlhandle;