This reverts https://github.com/matrix-org/synapse/pull/5732 which added unconditional
dependency on systemd.

diff --git a/contrib/systemd-with-workers/system/matrix-synapse-worker@.service b/contrib/systemd-with-workers/system/matrix-synapse-worker@.service
index 3507e2e..9d980d5 100644
--- a/contrib/systemd-with-workers/system/matrix-synapse-worker@.service
+++ b/contrib/systemd-with-workers/system/matrix-synapse-worker@.service
@@ -4,8 +4,7 @@ After=matrix-synapse.service
 BindsTo=matrix-synapse.service
 
 [Service]
-Type=notify
-NotifyAccess=main
+Type=simple
 User=matrix-synapse
 WorkingDirectory=/var/lib/matrix-synapse
 EnvironmentFile=/etc/default/matrix-synapse
diff --git a/contrib/systemd-with-workers/system/matrix-synapse.service b/contrib/systemd-with-workers/system/matrix-synapse.service
index 68e8991..3aae190 100644
--- a/contrib/systemd-with-workers/system/matrix-synapse.service
+++ b/contrib/systemd-with-workers/system/matrix-synapse.service
@@ -2,8 +2,7 @@
 Description=Synapse Matrix Homeserver
 
 [Service]
-Type=notify
-NotifyAccess=main
+Type=simple
 User=matrix-synapse
 WorkingDirectory=/var/lib/matrix-synapse
 EnvironmentFile=/etc/default/matrix-synapse
diff --git a/contrib/systemd/matrix-synapse.service b/contrib/systemd/matrix-synapse.service
index 38d369e..595b699 100644
--- a/contrib/systemd/matrix-synapse.service
+++ b/contrib/systemd/matrix-synapse.service
@@ -14,9 +14,7 @@
 Description=Synapse Matrix homeserver
 
 [Service]
-Type=notify
-NotifyAccess=main
-ExecReload=/bin/kill -HUP $MAINPID
+Type=simple
 Restart=on-abort
 
 User=synapse
diff --git a/synapse/app/_base.py b/synapse/app/_base.py
index c010e70..540dbd9 100644
--- a/synapse/app/_base.py
+++ b/synapse/app/_base.py
@@ -15,12 +15,10 @@
 
 import gc
 import logging
-import os
 import signal
 import sys
 import traceback
 
-import sdnotify
 from daemonize import Daemonize
 
 from twisted.internet import defer, error, reactor
@@ -244,16 +242,9 @@ def start(hs, listeners=None):
         if hasattr(signal, "SIGHUP"):
 
             def handle_sighup(*args, **kwargs):
-                # Tell systemd our state, if we're using it. This will silently fail if
-                # we're not using systemd.
-                sd_channel = sdnotify.SystemdNotifier()
-                sd_channel.notify("RELOADING=1")
-
                 for i in _sighup_callbacks:
                     i(hs)
 
-                sd_channel.notify("READY=1")
-
             signal.signal(signal.SIGHUP, handle_sighup)
 
             register_sighup(refresh_certificate)
@@ -269,7 +260,6 @@ def start(hs, listeners=None):
         hs.get_datastore().start_profiling()
 
         setup_sentry(hs)
-        setup_sdnotify(hs)
     except Exception:
         traceback.print_exc(file=sys.stderr)
         reactor = hs.get_reactor()
@@ -302,25 +292,6 @@ def setup_sentry(hs):
         scope.set_tag("worker_name", name)
 
 
-def setup_sdnotify(hs):
-    """Adds process state hooks to tell systemd what we are up to.
-    """
-
-    # Tell systemd our state, if we're using it. This will silently fail if
-    # we're not using systemd.
-    sd_channel = sdnotify.SystemdNotifier()
-
-    hs.get_reactor().addSystemEventTrigger(
-        "after",
-        "startup",
-        lambda: sd_channel.notify("READY=1\nMAINPID=%s" % (os.getpid())),
-    )
-
-    hs.get_reactor().addSystemEventTrigger(
-        "before", "shutdown", lambda: sd_channel.notify("STOPPING=1")
-    )
-
-
 def install_dns_limiter(reactor, max_dns_requests_in_flight=100):
     """Replaces the resolver with one that limits the number of in flight DNS
     requests.
diff --git a/synapse/app/appservice.py b/synapse/app/appservice.py
index 54bb114..e01f3e5 100644
--- a/synapse/app/appservice.py
+++ b/synapse/app/appservice.py
@@ -168,9 +168,7 @@ def start(config_options):
     )
 
     ps.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ps, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ps, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-appservice", config)
 
diff --git a/synapse/app/client_reader.py b/synapse/app/client_reader.py
index 721bb5b..29bddc4 100644
--- a/synapse/app/client_reader.py
+++ b/synapse/app/client_reader.py
@@ -194,9 +194,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-client-reader", config)
 
diff --git a/synapse/app/event_creator.py b/synapse/app/event_creator.py
index 473c889..042cfd0 100644
--- a/synapse/app/event_creator.py
+++ b/synapse/app/event_creator.py
@@ -193,9 +193,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-event-creator", config)
 
diff --git a/synapse/app/federation_reader.py b/synapse/app/federation_reader.py
index 5255d9e..76a97f8 100644
--- a/synapse/app/federation_reader.py
+++ b/synapse/app/federation_reader.py
@@ -175,9 +175,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-federation-reader", config)
 
diff --git a/synapse/app/federation_sender.py b/synapse/app/federation_sender.py
index c5a2880..fec49d5 100644
--- a/synapse/app/federation_sender.py
+++ b/synapse/app/federation_sender.py
@@ -198,9 +198,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-federation-sender", config)
 
diff --git a/synapse/app/frontend_proxy.py b/synapse/app/frontend_proxy.py
index e2822ca..3824964 100644
--- a/synapse/app/frontend_proxy.py
+++ b/synapse/app/frontend_proxy.py
@@ -247,9 +247,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-frontend-proxy", config)
 
diff --git a/synapse/app/homeserver.py b/synapse/app/homeserver.py
index 7d6b51b..8233905 100644
--- a/synapse/app/homeserver.py
+++ b/synapse/app/homeserver.py
@@ -447,7 +447,7 @@ def setup(config_options):
                 reactor.stop()
             sys.exit(1)
 
-    reactor.addSystemEventTrigger("before", "startup", start)
+    reactor.callWhenRunning(start)
 
     return hs
 
diff --git a/synapse/app/media_repository.py b/synapse/app/media_repository.py
index 3a16857..50c6d78 100644
--- a/synapse/app/media_repository.py
+++ b/synapse/app/media_repository.py
@@ -170,9 +170,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-media-repository", config)
 
diff --git a/synapse/app/pusher.py b/synapse/app/pusher.py
index 692ffa2..070de7d 100644
--- a/synapse/app/pusher.py
+++ b/synapse/app/pusher.py
@@ -216,7 +216,7 @@ def start(config_options):
         _base.start(ps, config.worker_listeners)
         ps.get_pusherpool().start()
 
-    reactor.addSystemEventTrigger("before", "startup", start)
+    reactor.callWhenRunning(start)
 
     _base.start_worker_reactor("synapse-pusher", config)
 
diff --git a/synapse/app/synchrotron.py b/synapse/app/synchrotron.py
index a1c3b16..315c030 100644
--- a/synapse/app/synchrotron.py
+++ b/synapse/app/synchrotron.py
@@ -451,9 +451,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-synchrotron", config)
 
diff --git a/synapse/app/user_dir.py b/synapse/app/user_dir.py
index cb29a1a..03ef21b 100644
--- a/synapse/app/user_dir.py
+++ b/synapse/app/user_dir.py
@@ -224,9 +224,7 @@ def start(config_options):
     )
 
     ss.setup()
-    reactor.addSystemEventTrigger(
-        "before", "startup", _base.start, ss, config.worker_listeners
-    )
+    reactor.callWhenRunning(_base.start, ss, config.worker_listeners)
 
     _base.start_worker_reactor("synapse-user-dir", config)
 
diff --git a/synapse/python_dependencies.py b/synapse/python_dependencies.py
index 195a7a7..c6465c0 100644
--- a/synapse/python_dependencies.py
+++ b/synapse/python_dependencies.py
@@ -72,7 +72,6 @@ REQUIREMENTS = [
     "netaddr>=0.7.18",
     "Jinja2>=2.9",
     "bleach>=1.4.3",
-    "sdnotify>=0.3",
 ]
 
 CONDITIONAL_REQUIREMENTS = {