OSF supports pthreads, per Philip Yarra.

bbac4188 · Tom Lane · 42df5e31 · bbac4188
Commit bbac4188 authored 21 years ago by Tom Lane
--- a/src/template/osf
+++ b/src/template/osf
@@ -4,3 +4,6 @@ else
  CC="$CC -std"
  CFLAGS='-O4 -Olimit 2000'
 fi
+SUPPORTS_THREADS=yes
+THREAD_CFLAGS="-pthread"
+