CLJ-823: Use release-pending-sends to avoid seque-into-seque deadlock

Signed-off-by: Stuart Halloway <[email protected]>

Author: jafingerhut

src/clj/clojure/core.clj

@@ -5111,6 +5111,7 @@
                       (do @agt nil)  ;touch agent just to propagate errors
                       (do
                         (send-off agt fill)
+                        (release-pending-sends)
                         (cons (if (identical? x NIL) nil x) (drain)))))))]
      (send-off agt fill)
      (drain))))

test/clojure/test_clojure/agents.clj

@@ -176,6 +176,13 @@
         (is (= (.size small-lbq)
                (dec queue-backlog)))))))
 
+;; Check for a deadlock condition when one seque was fed into another
+;; seque.  Note that this test does not throw an exception or
+;; otherwise fail if the issue is not fixed -- it simply deadlocks and
+;; hangs until killed.
+(deftest seque-into-seque-deadlock
+  (is (= (range 10) (seque 3 (seque 3 (range 10))))))
+
 ; http://clojure.org/agents
 
 ; agent