Add test case for circular reference SQPOLL hang

Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/.gitignore b/.gitignore
index f978b2f..d9fa2c2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -103,6 +103,7 @@
 /test/sq-poll-dup
 /test/sq-poll-kthread
 /test/sq-poll-share
+/test/sqpoll-exit-hang
 /test/sqpoll-sleep
 /test/sq-space_left
 /test/statx