There was a bug in lock handling when mixing INSERT ... SELECT on the same table.
mysql-test/suite/maria/insert_select.result:
Test case for MDEV_4010
mysql-test/suite/maria/insert_select.test:
Test case for MDEV_4010
mysys/thr_lock.c:
We wrongly alldoed TL_WRITE_CONCURRENT_INSERT when there was a TL_READ_NO_INSERT lock