sigTermHandler() tried to be careful to invoke only operations that
are safe to do in a signal handler. But for some reason we forgot
that exit(3) is not among those, because it calls atexit handlers
that might do various random things. (pg_dump itself installs no
atexit handlers, but e.g. OpenSSL does.) That led to crashes or
lockups when attempting to terminate a parallel dump or restore
via a signal.
Fix by calling _exit() instead.
Per bug #16199 from Raúl Marín. Back-patch to all supported branches.
Discussion: https://postgr.es/m/16199-cb2f121146a96f9b@postgresql.org
71b121f425