diff --git a/tornado/auth.py b/tornado/auth.py
index 32d0e226..ff7172aa 100644
--- a/tornado/auth.py
+++ b/tornado/auth.py
@@ -75,7 +75,7 @@ import hmac
 import time
 import uuid
 
-from tornado.concurrent import TracebackFuture, return_future
+from tornado.concurrent import TracebackFuture, return_future, chain_future
 from tornado import gen
 from tornado import httpclient
 from tornado import escape
@@ -985,7 +985,7 @@ class FacebookGraphMixin(OAuth2Mixin):
             future.set_exception(AuthError('Facebook auth error: %s' % str(response)))
             return
 
-        args = escape.parse_qs_bytes(escape.native_str(response.body))
+        args = urlparse.parse_qs(escape.native_str(response.body))
         session = {
             "access_token": args["access_token"][-1],
             "expires": args.get("expires")
@@ -1062,8 +1062,13 @@ class FacebookGraphMixin(OAuth2Mixin):
            Added the ability to override ``self._FACEBOOK_BASE_URL``.
         """
         url = self._FACEBOOK_BASE_URL + path
-        return self.oauth2_request(url, callback, access_token,
-                                   post_args, **args)
+        # Thanks to the _auth_return_future decorator, our "callback"
+        # argument is a Future, which we cannot pass as a callback to
+        # oauth2_request. Instead, have oauth2_request return a
+        # future and chain them together.
+        oauth_future = self.oauth2_request(url, access_token=access_token,
+                                           post_args=post_args, **args)
+        chain_future(oauth_future, callback)
 
 
 def _oauth_signature(consumer_token, method, url, parameters={}, token=None):

FacebookGraphMixin failing
I had to modify `_on_access_token` so that it did not attempt to make a `facebook_request` to `/me`. With the code as it stands, I get this error:

`TypeError: 'Future' object is not callable`

However, removing that extra request fixes this, and I can use the access_token in the next part of my auth pipeline.
diff --git a/tornado/test/auth_test.py b/tornado/test/auth_test.py
index 56de93a5..3ed40e45 100644
--- a/tornado/test/auth_test.py
+++ b/tornado/test/auth_test.py
@@ -5,7 +5,7 @@
 
 
 from __future__ import absolute_import, division, print_function, with_statement
-from tornado.auth import OpenIdMixin, OAuthMixin, OAuth2Mixin, TwitterMixin, AuthError, GoogleOAuth2Mixin
+from tornado.auth import OpenIdMixin, OAuthMixin, OAuth2Mixin, TwitterMixin, AuthError, GoogleOAuth2Mixin, FacebookGraphMixin
 from tornado.concurrent import Future
 from tornado.escape import json_decode
 from tornado import gen
@@ -126,6 +126,38 @@ class OAuth2ClientLoginHandler(RequestHandler, OAuth2Mixin):
         assert res.done()
 
 
+class FacebookClientLoginHandler(RequestHandler, FacebookGraphMixin):
+    def initialize(self, test):
+        self._OAUTH_AUTHORIZE_URL = test.get_url('/facebook/server/authorize')
+        self._OAUTH_ACCESS_TOKEN_URL = test.get_url('/facebook/server/access_token')
+        self._FACEBOOK_BASE_URL = test.get_url('/facebook/server')
+
+    @gen.coroutine
+    def get(self):
+        if self.get_argument("code", None):
+            user = yield self.get_authenticated_user(
+                redirect_uri=self.request.full_url(),
+                client_id=self.settings["facebook_api_key"],
+                client_secret=self.settings["facebook_secret"],
+                code=self.get_argument("code"))
+            self.write(user)
+        else:
+                yield self.authorize_redirect(
+                    redirect_uri=self.request.full_url(),
+                    client_id=self.settings["facebook_api_key"],
+                    extra_params={"scope": "read_stream,offline_access"})
+
+
+class FacebookServerAccessTokenHandler(RequestHandler):
+    def get(self):
+        self.write('access_token=asdf')
+
+
+class FacebookServerMeHandler(RequestHandler):
+    def get(self):
+        self.write('{}')
+
+
 class TwitterClientHandler(RequestHandler, TwitterMixin):
     def initialize(self, test):
         self._OAUTH_REQUEST_TOKEN_URL = test.get_url('/oauth1/server/request_token')
@@ -260,6 +292,8 @@ class AuthTest(AsyncHTTPTestCase):
                  dict(version='1.0a')),
                 ('/oauth2/client/login', OAuth2ClientLoginHandler, dict(test=self)),
 
+                ('/facebook/client/login', FacebookClientLoginHandler, dict(test=self)),
+
                 ('/twitter/client/login', TwitterClientLoginHandler, dict(test=self)),
                 ('/twitter/client/login_gen_engine', TwitterClientLoginGenEngineHandler, dict(test=self)),
                 ('/twitter/client/login_gen_coroutine', TwitterClientLoginGenCoroutineHandler, dict(test=self)),
@@ -271,13 +305,17 @@ class AuthTest(AsyncHTTPTestCase):
                 ('/oauth1/server/request_token', OAuth1ServerRequestTokenHandler),
                 ('/oauth1/server/access_token', OAuth1ServerAccessTokenHandler),
 
+                ('/facebook/server/access_token', FacebookServerAccessTokenHandler),
+                ('/facebook/server/me', FacebookServerMeHandler),
                 ('/twitter/server/access_token', TwitterServerAccessTokenHandler),
                 (r'/twitter/api/users/show/(.*)\.json', TwitterServerShowUserHandler),
                 (r'/twitter/api/account/verify_credentials\.json', TwitterServerVerifyCredentialsHandler),
             ],
             http_client=self.http_client,
             twitter_consumer_key='test_twitter_consumer_key',
-            twitter_consumer_secret='test_twitter_consumer_secret')
+            twitter_consumer_secret='test_twitter_consumer_secret',
+            facebook_api_key='test_facebook_api_key',
+            facebook_secret='test_facebook_secret')
 
     def test_openid_redirect(self):
         response = self.fetch('/openid/client/login', follow_redirects=False)
@@ -358,6 +396,13 @@ class AuthTest(AsyncHTTPTestCase):
         self.assertEqual(response.code, 302)
         self.assertTrue('/oauth2/server/authorize?' in response.headers['Location'])
 
+    def test_facebook_login(self):
+        response = self.fetch('/facebook/client/login', follow_redirects=False)
+        self.assertEqual(response.code, 302)
+        self.assertTrue('/facebook/server/authorize?' in response.headers['Location'])
+        response = self.fetch('/facebook/client/login?code=1234', follow_redirects=False)
+        self.assertEqual(response.code, 200)
+
     def base_twitter_redirect(self, url):
         # Same as test_oauth10a_redirect
         response = self.fetch(url, follow_redirects=False)

pip install -e .
parse_log_pytest
pytest
futures mock monotonic trollius pytest
apt-get update apt-get install -y gcc
3.5
pytest --no-header -rA --tb=line --color=no -p no:cacheprovider -W ignore::DeprecationWarning
attrs @ file:///opt/conda/conda-bld/attrs_1642510447205/work
certifi==2021.5.30
futures==2.2.0
importlib-metadata @ file:///tmp/build/80754af9/importlib-metadata_1631916693255/work
iniconfig @ file:///home/linux1/recipes/ci/iniconfig_1610983019677/work
mock==5.2.0
monotonic==1.6
more-itertools @ file:///tmp/build/80754af9/more-itertools_1637733554872/work
packaging @ file:///tmp/build/80754af9/packaging_1637314298585/work
pluggy @ file:///tmp/build/80754af9/pluggy_1615976315926/work
py @ file:///opt/conda/conda-bld/py_1644396412707/work
pyparsing @ file:///tmp/build/80754af9/pyparsing_1635766073266/work
pytest==6.2.4
six==1.17.0
toml @ file:///tmp/build/80754af9/toml_1616166611790/work
-e git+https://github.com/tornadoweb/tornado.git@4ee9ba94de11aaa4f932560fa2b3d8ceb8c61d2a#egg=tornado
trollius==2.1.post2
typing_extensions @ file:///opt/conda/conda-bld/typing_extensions_1647553014482/work
zipp @ file:///tmp/build/80754af9/zipp_1633618647012/work

name: tornado
channels:
  - defaults
  - https://repo.anaconda.com/pkgs/main
  - https://repo.anaconda.com/pkgs/r
  - conda-forge
dependencies:
  - _libgcc_mutex=0.1=main
  - _openmp_mutex=5.1=1_gnu
  - attrs=21.4.0=pyhd3eb1b0_0
  - ca-certificates=2025.2.25=h06a4308_0
  - certifi=2021.5.30=py36h06a4308_0
  - importlib-metadata=4.8.1=py36h06a4308_0
  - importlib_metadata=4.8.1=hd3eb1b0_0
  - iniconfig=1.1.1=pyhd3eb1b0_0
  - ld_impl_linux-64=2.40=h12ee557_0
  - libffi=3.3=he6710b0_2
  - libgcc-ng=11.2.0=h1234567_1
  - libgomp=11.2.0=h1234567_1
  - libstdcxx-ng=11.2.0=h1234567_1
  - more-itertools=8.12.0=pyhd3eb1b0_0
  - ncurses=6.4=h6a678d5_0
  - openssl=1.1.1w=h7f8727e_0
  - packaging=21.3=pyhd3eb1b0_0
  - pip=21.2.2=py36h06a4308_0
  - pluggy=0.13.1=py36h06a4308_0
  - py=1.11.0=pyhd3eb1b0_0
  - pyparsing=3.0.4=pyhd3eb1b0_0
  - pytest=6.2.4=py36h06a4308_2
  - python=3.6.13=h12debd9_1
  - readline=8.2=h5eee18b_0
  - setuptools=58.0.4=py36h06a4308_0
  - sqlite=3.45.3=h5eee18b_0
  - tk=8.6.14=h39e8969_0
  - toml=0.10.2=pyhd3eb1b0_0
  - typing_extensions=4.1.1=pyh06a4308_0
  - wheel=0.37.1=pyhd3eb1b0_0
  - xz=5.6.4=h5eee18b_1
  - zipp=3.6.0=pyhd3eb1b0_0
  - zlib=1.2.13=h5eee18b_1
  - pip:
      - futures==2.2.0
      - mock==5.2.0
      - monotonic==1.6
      - six==1.17.0
      - trollius==2.1.post2
prefix: /opt/conda/envs/tornado

tornado/test/auth_test.py::AuthTest::test_facebook_login
tornado/test/auth_test.py::AuthTest::test_oauth10_get_user tornado/test/auth_test.py::AuthTest::test_oauth10_redirect tornado/test/auth_test.py::AuthTest::test_oauth10_request_parameters tornado/test/auth_test.py::AuthTest::test_oauth10a_get_user tornado/test/auth_test.py::AuthTest::test_oauth10a_get_user_coroutine_exception tornado/test/auth_test.py::AuthTest::test_oauth10a_redirect tornado/test/auth_test.py::AuthTest::test_oauth10a_request_parameters tornado/test/auth_test.py::AuthTest::test_oauth2_redirect tornado/test/auth_test.py::AuthTest::test_openid_get_user tornado/test/auth_test.py::AuthTest::test_openid_redirect tornado/test/auth_test.py::AuthTest::test_twitter_get_user tornado/test/auth_test.py::AuthTest::test_twitter_redirect tornado/test/auth_test.py::AuthTest::test_twitter_redirect_gen_coroutine tornado/test/auth_test.py::AuthTest::test_twitter_redirect_gen_engine tornado/test/auth_test.py::AuthTest::test_twitter_show_user tornado/test/auth_test.py::AuthTest::test_twitter_show_user_error tornado/test/auth_test.py::AuthTest::test_twitter_show_user_future tornado/test/auth_test.py::AuthTest::test_twitter_show_user_future_error tornado/test/auth_test.py::GoogleOAuth2Test::test_google_login
tornado/auth.py
tornado/auth.py