I can reproduce the bug on the master branch with the following steps:
1. Apply 0001-XXX-Dirty-hack-to-clobber-control-file-for-testing.patch [1]
2. Compile PostgreSQL with `-DEXEC_BACKEND` C compiler flag option.
3. Run `initdb`
4. Run `postgres`
5. Run `pgbench -i`
6. Run `psql -c 'do $$ begin loop perform pg_update_control_file(); end
loop; end; $$;'`
7. Run `for run in {1..5000}; do pgbench -c50 -t100 -j6 -S postgres; done`
in parallel with the previous command.
8. Wait a while.
[1]
https://www.postgresql.org/message-id/CA%2BhUKGK-BEe38aKNqHJDQ86LUW-CMwF5F9bo1JtJVg71FoDv_w%40mail.gmail.com
