This one crashes Pyston reliably

test/tests/thread_contention_test.py

+# skip-if: True
+# - Pyston is not yet thread safe.  this test sometimes works and sometimes doesn't.
+# - threads also seem to cause much greater memory usage for both CPython and Pyston and
+#   blow out the memory limits set by the tester.
+
+from thread import start_new_thread
+import time
+
+work = []
+done = []
+def run(num):
+    work.append(num)
+    for i in xrange(num):
+        t = work.pop()
+        work.append(t - 1)
+    done.append(num)
+
+print "starting!"
+
+nthreads = 2
+for i in xrange(nthreads):
+    t = start_new_thread(run, (1000000,))
+
+while len(done) < nthreads:
+    time.sleep(0)
+
+print work, sum(work)