High concurrency can lock up PrimProc

On my 32vcore machine running 64 parallel queries has a high probability of completely locking up PrimProc.

My theory is the threads are requesting access to the thread pool for BPP jobs but the thread pool is already maxed out. Causing a wait deadlock.

Test is using:

mysqlslap -c64 --number-of-queries=640 --query="select dt, count(*) from test.t1 group by dt" --user=root --socket=/usr/local/mariadb/columnstore/mysql/lib/mysql/mysql.sock"

Test schema and data will be attached shortly.