Index: sys/dev/hyperv/vmbus/hv_ring_buffer.c
===================================================================
--- sys/dev/hyperv/vmbus/hv_ring_buffer.c
+++ sys/dev/hyperv/vmbus/hv_ring_buffer.c
@@ -247,7 +247,7 @@
 	ring_info->ring_size = buffer_len;
 	ring_info->ring_data_size = buffer_len - sizeof(hv_vmbus_ring_buffer);
 
-	mtx_init(&ring_info->ring_lock, "vmbus ring buffer", NULL, MTX_SPIN);
+	mtx_init(&ring_info->ring_lock, "vmbus ring buffer", NULL, MTX_DEF);
 
 	return (0);
 }
@@ -285,7 +285,7 @@
 
 	total_bytes_to_write += sizeof(uint64_t);
 
-	mtx_lock_spin(&out_ring_info->ring_lock);
+	mtx_lock(&out_ring_info->ring_lock);
 
 	get_ring_buffer_avail_bytes(out_ring_info, &byte_avail_to_read,
 	    &byte_avail_to_write);
@@ -298,7 +298,7 @@
 
 	if (byte_avail_to_write <= total_bytes_to_write) {
 
-	    mtx_unlock_spin(&out_ring_info->ring_lock);
+	    mtx_unlock(&out_ring_info->ring_lock);
 	    return (EAGAIN);
 	}
 
@@ -334,7 +334,7 @@
 	 */
 	set_next_write_location(out_ring_info, next_write_location);
 
-	mtx_unlock_spin(&out_ring_info->ring_lock);
+	mtx_unlock(&out_ring_info->ring_lock);
 
 	*need_sig = hv_ring_buffer_needsig_on_write(old_write_location,
 	    out_ring_info);
@@ -355,8 +355,6 @@
 	uint32_t bytesAvailToRead;
 	uint32_t nextReadLocation = 0;
 
-	mtx_lock_spin(&in_ring_info->ring_lock);
-
 	get_ring_buffer_avail_bytes(in_ring_info, &bytesAvailToRead,
 		&bytesAvailToWrite);
 
@@ -364,7 +362,6 @@
 	 * Make sure there is something to read
 	 */
 	if (bytesAvailToRead < buffer_len) {
-	    mtx_unlock_spin(&in_ring_info->ring_lock);
 	    return (EAGAIN);
 	}
 
@@ -376,8 +373,6 @@
 	nextReadLocation = copy_from_ring_buffer(
 		in_ring_info, (char *)buffer, buffer_len, nextReadLocation);
 
-	mtx_unlock_spin(&in_ring_info->ring_lock);
-
 	return (0);
 }
 
@@ -399,8 +394,6 @@
 	if (buffer_len <= 0)
 	    return (EINVAL);
 
-	mtx_lock_spin(&in_ring_info->ring_lock);
-
 	get_ring_buffer_avail_bytes(
 	    in_ring_info, &bytes_avail_to_read,
 	    &bytes_avail_to_write);
@@ -409,7 +402,6 @@
 	 * Make sure there is something to read
 	 */
 	if (bytes_avail_to_read < buffer_len) {
-	    mtx_unlock_spin(&in_ring_info->ring_lock);
 	    return (EAGAIN);
 	}
 
@@ -441,8 +433,6 @@
 	 */
 	set_next_read_location(in_ring_info, next_read_location);
 
-	mtx_unlock_spin(&in_ring_info->ring_lock);
-
 	return (0);
 }