diff --git a/lower-constraints.txt b/lower-constraints.txt
index 65618eb..c53df18 100644
--- a/lower-constraints.txt
+++ b/lower-constraints.txt
@@ -6,7 +6,7 @@ cffi==1.7.0
 debtcollector==1.2.0
 docutils==0.11
 dulwich==0.15.0
-eventlet==0.18.2
+eventlet==0.21.0
 extras==1.0.0
 fixtures==3.0.0
 gitdb==0.6.4
diff --git a/oslo_privsep/daemon.py b/oslo_privsep/daemon.py
index 1cf4145..3297e72 100644
--- a/oslo_privsep/daemon.py
+++ b/oslo_privsep/daemon.py
@@ -57,6 +57,7 @@ import tempfile
 import threading
 
 import eventlet
+from eventlet import patcher
 from oslo_config import cfg
 from oslo_log import log as logging
 from oslo_utils import encodeutils
@@ -75,6 +76,25 @@ if platform.system() == 'Linux':
 LOG = logging.getLogger(__name__)
 
 
+EVENTLET_MODULES = ('os', 'select', 'socket', 'thread', 'time', 'MySQLdb',
+                    'builtins', 'subprocess')
+EVENTLET_LIBRARIES = []
+
+
+def _null():
+    return []
+
+
+for module in EVENTLET_MODULES:
+    if hasattr(patcher, '_green_%s_modules' % module):
+        method = getattr(patcher, '_green_%s_modules' % module)
+    elif hasattr(patcher, '_green_%s' % module):
+        method = getattr(patcher, '_green_%s' % module)
+    else:
+        method = _null()
+    EVENTLET_LIBRARIES.append((module, method))
+
+
 @enum.unique
 class StdioFd(enum.IntEnum):
     # NOTE(gus): We can't use sys.std*.fileno() here.  sys.std*
@@ -258,6 +278,21 @@ def replace_logging(handler, log_root=None):
     log_root.addHandler(handler)
 
 
+def un_monkey_patch():
+    for eventlet_mod_name, func_modules in EVENTLET_LIBRARIES:
+        if not eventlet.patcher.is_monkey_patched(eventlet_mod_name):
+            continue
+
+        for name, mod in func_modules():
+            patched_mod = sys.modules.get(name)
+            orig_mod = eventlet.patcher.original(name)
+            for attr_name in mod.__patched__:
+                patched_attr = getattr(mod, attr_name, None)
+                unpatched_attr = getattr(orig_mod, attr_name, None)
+                if patched_attr is not None:
+                    setattr(patched_mod, attr_name, unpatched_attr)
+
+
 class ForkingClientChannel(_ClientChannel):
     def __init__(self, context):
         """Start privsep daemon using fork()
@@ -279,6 +314,7 @@ class ForkingClientChannel(_ClientChannel):
 
         if os.fork() == 0:
             # child
+            un_monkey_patch()
 
             channel = comm.ServerChannel(sock_b)
             sock_a.close()
diff --git a/oslo_privsep/tests/test_daemon.py b/oslo_privsep/tests/test_daemon.py
index b39ce61..01eb52b 100644
--- a/oslo_privsep/tests/test_daemon.py
+++ b/oslo_privsep/tests/test_daemon.py
@@ -13,6 +13,7 @@
 #    under the License.
 
 import copy
+import eventlet
 import fixtures
 import functools
 import logging as pylogging
@@ -215,3 +216,30 @@ class ClientChannelTestCase(base.BaseTestCase):
         with mock.patch.object(daemon.LOG, 'warning') as mock_warning:
             self.client_channel.out_of_band([daemon.Message.PING])
             mock_warning.assert_called_once()
+
+
+class UnMonkeyPatch(base.BaseTestCase):
+
+    def test_un_monkey_patch(self):
+        self.assertFalse(any(
+            eventlet.patcher.is_monkey_patched(eventlet_mod_name)
+            for eventlet_mod_name in daemon.EVENTLET_MODULES))
+
+        eventlet.monkey_patch()
+        self.assertTrue(any(
+            eventlet.patcher.is_monkey_patched(eventlet_mod_name)
+            for eventlet_mod_name in daemon.EVENTLET_MODULES))
+
+        daemon.un_monkey_patch()
+        for eventlet_mod_name, func_modules in daemon.EVENTLET_LIBRARIES:
+            if not eventlet.patcher.is_monkey_patched(eventlet_mod_name):
+                continue
+
+            for name, green_mod in func_modules():
+                orig_mod = eventlet.patcher.original(name)
+                patched_mod = sys.modules.get(name)
+                for attr_name in green_mod.__patched__:
+                    un_monkey_patched_attr = getattr(patched_mod, attr_name,
+                                                     None)
+                    original_attr = getattr(orig_mod, attr_name, None)
+                    self.assertEqual(un_monkey_patched_attr, original_attr)
diff --git a/releasenotes/notes/un-monkey-patch-privileged-daemon-160e00296549df3d.yaml b/releasenotes/notes/un-monkey-patch-privileged-daemon-160e00296549df3d.yaml
new file mode 100644
index 0000000..3f00ef8
--- /dev/null
+++ b/releasenotes/notes/un-monkey-patch-privileged-daemon-160e00296549df3d.yaml
@@ -0,0 +1,11 @@
+---
+other:
+  - |
+    The ``oslo.privsep`` client can be called from a program using eventlet.
+    If ``eventlet.monkey_patch``, some libraries will be patched, for example
+    ``threading`` or ``os``. When the root daemon is forked from the client
+    process, those libraries remain patched. Now, when the daemon is forked
+    from the client process, those libraries and methods are restored to the
+    original values. The goal is to prevent some timeouts when using eventlet
+    threads (user threads); system threads are preemptive and the code does
+    not need to care about the executor token.
diff --git a/requirements.txt b/requirements.txt
index 7228b1a..8541ac3 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -7,6 +7,6 @@ oslo.i18n>=3.15.3 # Apache-2.0
 oslo.config>=5.2.0 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0
 cffi>=1.7.0 # MIT
-eventlet!=0.18.3,!=0.20.1,>=0.18.2 # MIT
+eventlet>=0.21.0 # MIT
 greenlet>=0.4.14 # MIT
 msgpack>=0.6.0 # Apache-2.0