diff --git a/Lib/test/test_file.py b/Lib/test/test_file.py
index 3ae460c..aab3e70 100644
--- a/Lib/test/test_file.py
+++ b/Lib/test/test_file.py
@@ -1,9 +1,13 @@
 import sys
 import os
 import unittest
+import itertools
+import time
+import threading
 from array import array
 from weakref import proxy
 
+from test import test_support
 from test.test_support import TESTFN, findfile, run_unittest
 from UserList import UserList
 
@@ -339,11 +343,173 @@
         self.failUnless(f.subclass_closed)
 
 
+class FileThreadingTests(unittest.TestCase):
+    # These tests check the ability to call various methods of file objects
+    # (including close()) concurrently without crashing the Python interpreter.
+    # See #815646, #595601
+
+    def setUp(self):
+        self.f = None
+        self.filename = TESTFN
+        with open(self.filename, "w") as f:
+            f.write("\n".join("0123456789"))
+        self._count_lock = threading.Lock()
+        self.close_count = 0
+        self.close_success_count = 0
+
+    def tearDown(self):
+        if self.f:
+            try:
+                self.f.close()
+            except (EnvironmentError, ValueError):
+                pass
+        try:
+            os.remove(self.filename)
+        except EnvironmentError:
+            pass
+
+    def _create_file(self):
+        self.f = open(self.filename, "w+")
+
+    def _close_file(self):
+        with self._count_lock:
+            self.close_count += 1
+        self.f.close()
+        with self._count_lock:
+            self.close_success_count += 1
+
+    def _close_and_reopen_file(self):
+        self._close_file()
+        # if close raises an exception thats fine, self.f remains valid so
+        # we don't need to reopen.
+        self._create_file()
+
+    def _run_workers(self, func, nb_workers, duration=0.2):
+        with self._count_lock:
+            self.close_count = 0
+            self.close_success_count = 0
+        self.do_continue = True
+        threads = []
+        try:
+            for i in range(nb_workers):
+                t = threading.Thread(target=func)
+                t.start()
+                threads.append(t)
+            for _ in xrange(100):
+                time.sleep(duration/100)
+                with self._count_lock:
+                    if self.close_count-self.close_success_count > nb_workers+1:
+                        if test_support.verbose:
+                            print 'Q',
+                        break
+            time.sleep(duration)
+        finally:
+            self.do_continue = False
+            for t in threads:
+                t.join()
+
+    def _test_close_open_io(self, io_func, nb_workers=5):
+        def worker():
+            self._create_file()
+            funcs = itertools.cycle((
+                lambda: io_func(),
+                lambda: self._close_and_reopen_file(),
+            ))
+            for f in funcs:
+                if not self.do_continue:
+                    break
+                try:
+                    f()
+                except (IOError, ValueError):
+                    pass
+        self._run_workers(worker, nb_workers)
+        if test_support.verbose:
+            # Useful verbose statistics when tuning this test to take
+            # less time to run but still ensuring that its still useful.
+            #
+            # the percent of close calls that raised an error
+            percent = 100. - 100.*self.close_success_count/self.close_count
+            print self.close_count, ('%.4f ' % percent),
+
+    def test_close_open(self):
+        def io_func():
+            pass
+        self._test_close_open_io(io_func)
+
+    def test_close_open_flush(self):
+        def io_func():
+            self.f.flush()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_iter(self):
+        def io_func():
+            list(iter(self.f))
+        self._test_close_open_io(io_func)
+
+    def test_close_open_isatty(self):
+        def io_func():
+            self.f.isatty()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_print(self):
+        def io_func():
+            print >> self.f, ''
+        self._test_close_open_io(io_func)
+
+    def test_close_open_read(self):
+        def io_func():
+            self.f.read(0)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readinto(self):
+        def io_func():
+            a = array('c', 'xxxxx')
+            self.f.readinto(a)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readline(self):
+        def io_func():
+            self.f.readline()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_readlines(self):
+        def io_func():
+            self.f.readlines()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_seek(self):
+        def io_func():
+            self.f.seek(0, 0)
+        self._test_close_open_io(io_func)
+
+    def test_close_open_tell(self):
+        def io_func():
+            self.f.tell()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_truncate(self):
+        def io_func():
+            self.f.truncate()
+        self._test_close_open_io(io_func)
+
+    def test_close_open_write(self):
+        def io_func():
+            self.f.write('')
+        self._test_close_open_io(io_func)
+
+    def test_close_open_writelines(self):
+        def io_func():
+            self.f.writelines('')
+        self._test_close_open_io(io_func)
+
+
+
 def test_main():
     # Historically, these tests have been sloppy about removing TESTFN.
     # So get rid of it no matter what.
     try:
-        run_unittest(AutoFileTests, OtherFileTests, FileSubclassTests)
+        run_unittest(AutoFileTests, OtherFileTests, FileSubclassTests,
+            FileThreadingTests)
     finally:
         if os.path.exists(TESTFN):
             os.unlink(TESTFN)