Why unlock before executing write?

[wongkq]

skiboot/core/console.c

Line 151 in 8fe7ea7

unlock(&con_lock);

skiboot/core/console.c

Line 152 in 8fe7ea7

len = con_driver->write(con_buf + con_out, req);

skiboot/core/console.c

Line 153 in 8fe7ea7

lock(&con_lock);

Why unlock before executing write here?