If 6 gets inserted before 7, then we lose 6 as 5->next will be set to 7 by the second thread after 6 is inserted.
And the other way round as well. If 7 gets inserted before 6, then we lose 7. As 5->next will be set to 6.
If 6 gets inserted before 7, then we lose 6 as 5->next will be set to 7 by the second thread after 6 is inserted.
And the other way round as well. If 7 gets inserted before 6, then we lose 7. As 5->next will be set to 6.