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-rw-r--r--synapse/federation/federation_server.py10
-rw-r--r--synapse/handlers/appservice.py6
-rw-r--r--synapse/handlers/device.py2
-rw-r--r--synapse/handlers/e2e_keys.py4
-rw-r--r--synapse/handlers/e2e_room_keys.py14
-rw-r--r--synapse/handlers/federation.py2
-rw-r--r--synapse/handlers/federation_event.py2
-rw-r--r--synapse/handlers/message.py2
-rw-r--r--synapse/handlers/presence.py4
-rw-r--r--synapse/handlers/read_marker.py2
-rw-r--r--synapse/handlers/room.py2
-rw-r--r--synapse/handlers/room_member.py4
-rw-r--r--synapse/handlers/sso.py2
-rw-r--r--synapse/push/bulk_push_rule_evaluator.py2
-rw-r--r--synapse/replication/tcp/client.py2
-rw-r--r--synapse/rest/media/v1/media_repository.py6
-rw-r--r--synapse/state/__init__.py2
-rw-r--r--synapse/storage/databases/main/roommember.py2
-rw-r--r--synapse/util/async_helpers.py144
19 files changed, 101 insertions, 113 deletions
diff --git a/synapse/federation/federation_server.py b/synapse/federation/federation_server.py
index c7400c737b..69d833585f 100644
--- a/synapse/federation/federation_server.py
+++ b/synapse/federation/federation_server.py
@@ -188,7 +188,7 @@ class FederationServer(FederationBase):
     async def on_backfill_request(
         self, origin: str, room_id: str, versions: List[str], limit: int
     ) -> Tuple[int, Dict[str, Any]]:
-        with (await self._server_linearizer.queue((origin, room_id))):
+        async with self._server_linearizer.queue((origin, room_id)):
             origin_host, _ = parse_server_name(origin)
             await self.check_server_matches_acl(origin_host, room_id)
 
@@ -218,7 +218,7 @@ class FederationServer(FederationBase):
             Tuple indicating the response status code and dictionary response
             body including `event_id`.
         """
-        with (await self._server_linearizer.queue((origin, room_id))):
+        async with self._server_linearizer.queue((origin, room_id)):
             origin_host, _ = parse_server_name(origin)
             await self.check_server_matches_acl(origin_host, room_id)
 
@@ -529,7 +529,7 @@ class FederationServer(FederationBase):
         # in the cache so we could return it without waiting for the linearizer
         # - but that's non-trivial to get right, and anyway somewhat defeats
         # the point of the linearizer.
-        with (await self._server_linearizer.queue((origin, room_id))):
+        async with self._server_linearizer.queue((origin, room_id)):
             resp: JsonDict = dict(
                 await self._state_resp_cache.wrap(
                     (room_id, event_id),
@@ -883,7 +883,7 @@ class FederationServer(FederationBase):
     async def on_event_auth(
         self, origin: str, room_id: str, event_id: str
     ) -> Tuple[int, Dict[str, Any]]:
-        with (await self._server_linearizer.queue((origin, room_id))):
+        async with self._server_linearizer.queue((origin, room_id)):
             origin_host, _ = parse_server_name(origin)
             await self.check_server_matches_acl(origin_host, room_id)
 
@@ -945,7 +945,7 @@ class FederationServer(FederationBase):
         latest_events: List[str],
         limit: int,
     ) -> Dict[str, list]:
-        with (await self._server_linearizer.queue((origin, room_id))):
+        async with self._server_linearizer.queue((origin, room_id)):
             origin_host, _ = parse_server_name(origin)
             await self.check_server_matches_acl(origin_host, room_id)
 
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 316c4b677c..1b57840506 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -330,10 +330,8 @@ class ApplicationServicesHandler:
                     continue
 
                 # Since we read/update the stream position for this AS/stream
-                with (
-                    await self._ephemeral_events_linearizer.queue(
-                        (service.id, stream_key)
-                    )
+                async with self._ephemeral_events_linearizer.queue(
+                    (service.id, stream_key)
                 ):
                     if stream_key == "receipt_key":
                         events = await self._handle_receipts(service, new_token)
diff --git a/synapse/handlers/device.py b/synapse/handlers/device.py
index c710c02cf9..ffa28b2a30 100644
--- a/synapse/handlers/device.py
+++ b/synapse/handlers/device.py
@@ -833,7 +833,7 @@ class DeviceListUpdater:
     async def _handle_device_updates(self, user_id: str) -> None:
         "Actually handle pending updates."
 
-        with (await self._remote_edu_linearizer.queue(user_id)):
+        async with self._remote_edu_linearizer.queue(user_id):
             pending_updates = self._pending_updates.pop(user_id, [])
             if not pending_updates:
                 # This can happen since we batch updates
diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py
index d96456cd40..d6714228ef 100644
--- a/synapse/handlers/e2e_keys.py
+++ b/synapse/handlers/e2e_keys.py
@@ -118,7 +118,7 @@ class E2eKeysHandler:
             from_device_id: the device making the query. This is used to limit
                 the number of in-flight queries at a time.
         """
-        with await self._query_devices_linearizer.queue((from_user_id, from_device_id)):
+        async with self._query_devices_linearizer.queue((from_user_id, from_device_id)):
             device_keys_query: Dict[str, Iterable[str]] = query_body.get(
                 "device_keys", {}
             )
@@ -1386,7 +1386,7 @@ class SigningKeyEduUpdater:
         device_handler = self.e2e_keys_handler.device_handler
         device_list_updater = device_handler.device_list_updater
 
-        with (await self._remote_edu_linearizer.queue(user_id)):
+        async with self._remote_edu_linearizer.queue(user_id):
             pending_updates = self._pending_updates.pop(user_id, [])
             if not pending_updates:
                 # This can happen since we batch updates
diff --git a/synapse/handlers/e2e_room_keys.py b/synapse/handlers/e2e_room_keys.py
index 52e44a2d42..446f509bdc 100644
--- a/synapse/handlers/e2e_room_keys.py
+++ b/synapse/handlers/e2e_room_keys.py
@@ -83,7 +83,7 @@ class E2eRoomKeysHandler:
 
         # we deliberately take the lock to get keys so that changing the version
         # works atomically
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             # make sure the backup version exists
             try:
                 await self.store.get_e2e_room_keys_version_info(user_id, version)
@@ -126,7 +126,7 @@ class E2eRoomKeysHandler:
         """
 
         # lock for consistency with uploading
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             # make sure the backup version exists
             try:
                 version_info = await self.store.get_e2e_room_keys_version_info(
@@ -187,7 +187,7 @@ class E2eRoomKeysHandler:
         # TODO: Validate the JSON to make sure it has the right keys.
 
         # XXX: perhaps we should use a finer grained lock here?
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
 
             # Check that the version we're trying to upload is the current version
             try:
@@ -332,7 +332,7 @@ class E2eRoomKeysHandler:
         # TODO: Validate the JSON to make sure it has the right keys.
 
         # lock everyone out until we've switched version
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             new_version = await self.store.create_e2e_room_keys_version(
                 user_id, version_info
             )
@@ -359,7 +359,7 @@ class E2eRoomKeysHandler:
         }
         """
 
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             try:
                 res = await self.store.get_e2e_room_keys_version_info(user_id, version)
             except StoreError as e:
@@ -383,7 +383,7 @@ class E2eRoomKeysHandler:
             NotFoundError: if this backup version doesn't exist
         """
 
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             try:
                 await self.store.delete_e2e_room_keys_version(user_id, version)
             except StoreError as e:
@@ -413,7 +413,7 @@ class E2eRoomKeysHandler:
             raise SynapseError(
                 400, "Version in body does not match", Codes.INVALID_PARAM
             )
-        with (await self._upload_linearizer.queue(user_id)):
+        async with self._upload_linearizer.queue(user_id):
             try:
                 old_info = await self.store.get_e2e_room_keys_version_info(
                     user_id, version
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index 350ec9c03a..78d149905f 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -151,7 +151,7 @@ class FederationHandler:
                 return. This is used as part of the heuristic to decide if we
                 should back paginate.
         """
-        with (await self._room_backfill.queue(room_id)):
+        async with self._room_backfill.queue(room_id):
             return await self._maybe_backfill_inner(room_id, current_depth, limit)
 
     async def _maybe_backfill_inner(
diff --git a/synapse/handlers/federation_event.py b/synapse/handlers/federation_event.py
index e7b9f15e13..03c1197c99 100644
--- a/synapse/handlers/federation_event.py
+++ b/synapse/handlers/federation_event.py
@@ -224,7 +224,7 @@ class FederationEventHandler:
                     len(missing_prevs),
                     shortstr(missing_prevs),
                 )
-                with (await self._room_pdu_linearizer.queue(pdu.room_id)):
+                async with self._room_pdu_linearizer.queue(pdu.room_id):
                     logger.info(
                         "Acquired room lock to fetch %d missing prev_events",
                         len(missing_prevs),
diff --git a/synapse/handlers/message.py b/synapse/handlers/message.py
index 766f597a55..7db6905c61 100644
--- a/synapse/handlers/message.py
+++ b/synapse/handlers/message.py
@@ -851,7 +851,7 @@ class EventCreationHandler:
         # a situation where event persistence can't keep up, causing
         # extremities to pile up, which in turn leads to state resolution
         # taking longer.
-        with (await self.limiter.queue(event_dict["room_id"])):
+        async with self.limiter.queue(event_dict["room_id"]):
             if txn_id and requester.access_token_id:
                 existing_event_id = await self.store.get_event_id_from_transaction_id(
                     event_dict["room_id"],
diff --git a/synapse/handlers/presence.py b/synapse/handlers/presence.py
index dace31d87e..209a4b0e52 100644
--- a/synapse/handlers/presence.py
+++ b/synapse/handlers/presence.py
@@ -1030,7 +1030,7 @@ class PresenceHandler(BasePresenceHandler):
             is_syncing: Whether or not the user is now syncing
             sync_time_msec: Time in ms when the user was last syncing
         """
-        with (await self.external_sync_linearizer.queue(process_id)):
+        async with self.external_sync_linearizer.queue(process_id):
             prev_state = await self.current_state_for_user(user_id)
 
             process_presence = self.external_process_to_current_syncs.setdefault(
@@ -1071,7 +1071,7 @@ class PresenceHandler(BasePresenceHandler):
 
         Used when the process has stopped/disappeared.
         """
-        with (await self.external_sync_linearizer.queue(process_id)):
+        async with self.external_sync_linearizer.queue(process_id):
             process_presence = self.external_process_to_current_syncs.pop(
                 process_id, set()
             )
diff --git a/synapse/handlers/read_marker.py b/synapse/handlers/read_marker.py
index bad1acc634..05122fd5a6 100644
--- a/synapse/handlers/read_marker.py
+++ b/synapse/handlers/read_marker.py
@@ -40,7 +40,7 @@ class ReadMarkerHandler:
         the read marker has changed.
         """
 
-        with await self.read_marker_linearizer.queue((room_id, user_id)):
+        async with self.read_marker_linearizer.queue((room_id, user_id)):
             existing_read_marker = await self.store.get_account_data_for_room_and_type(
                 user_id, room_id, "m.fully_read"
             )
diff --git a/synapse/handlers/room.py b/synapse/handlers/room.py
index 51a08fd2c0..65d4aea9af 100644
--- a/synapse/handlers/room.py
+++ b/synapse/handlers/room.py
@@ -883,7 +883,7 @@ class RoomCreationHandler:
         #
         # we also don't need to check the requester's shadow-ban here, as we
         # have already done so above (and potentially emptied invite_list).
-        with (await self.room_member_handler.member_linearizer.queue((room_id,))):
+        async with self.room_member_handler.member_linearizer.queue((room_id,)):
             content = {}
             is_direct = config.get("is_direct", None)
             if is_direct:
diff --git a/synapse/handlers/room_member.py b/synapse/handlers/room_member.py
index 0785e31114..802e57c4d0 100644
--- a/synapse/handlers/room_member.py
+++ b/synapse/handlers/room_member.py
@@ -515,8 +515,8 @@ class RoomMemberHandler(metaclass=abc.ABCMeta):
 
         # We first linearise by the application service (to try to limit concurrent joins
         # by application services), and then by room ID.
-        with (await self.member_as_limiter.queue(as_id)):
-            with (await self.member_linearizer.queue(key)):
+        async with self.member_as_limiter.queue(as_id):
+            async with self.member_linearizer.queue(key):
                 result = await self.update_membership_locked(
                     requester,
                     target,
diff --git a/synapse/handlers/sso.py b/synapse/handlers/sso.py
index 4f02a060d9..e4fe94e557 100644
--- a/synapse/handlers/sso.py
+++ b/synapse/handlers/sso.py
@@ -430,7 +430,7 @@ class SsoHandler:
         # grab a lock while we try to find a mapping for this user. This seems...
         # optimistic, especially for implementations that end up redirecting to
         # interstitial pages.
-        with await self._mapping_lock.queue(auth_provider_id):
+        async with self._mapping_lock.queue(auth_provider_id):
             # first of all, check if we already have a mapping for this user
             user_id = await self.get_sso_user_by_remote_user_id(
                 auth_provider_id,
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index a402a3e403..b07cf2eee7 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -397,7 +397,7 @@ class RulesForRoom:
             self.room_push_rule_cache_metrics.inc_hits()
             return self.data.rules_by_user
 
-        with (await self.linearizer.queue(self.room_id)):
+        async with self.linearizer.queue(self.room_id):
             if state_group and self.data.state_group == state_group:
                 logger.debug("Using cached rules for %r", self.room_id)
                 self.room_push_rule_cache_metrics.inc_hits()
diff --git a/synapse/replication/tcp/client.py b/synapse/replication/tcp/client.py
index deeaaec4e6..122892c7bc 100644
--- a/synapse/replication/tcp/client.py
+++ b/synapse/replication/tcp/client.py
@@ -451,7 +451,7 @@ class FederationSenderHandler:
             # service for robustness? Or could we replace it with an assertion that
             # we're not being re-entered?
 
-            with (await self._fed_position_linearizer.queue(None)):
+            async with self._fed_position_linearizer.queue(None):
                 # We persist and ack the same position, so we take a copy of it
                 # here as otherwise it can get modified from underneath us.
                 current_position = self.federation_position
diff --git a/synapse/rest/media/v1/media_repository.py b/synapse/rest/media/v1/media_repository.py
index 6c414402bd..3e5d6c6294 100644
--- a/synapse/rest/media/v1/media_repository.py
+++ b/synapse/rest/media/v1/media_repository.py
@@ -258,7 +258,7 @@ class MediaRepository:
         # We linearize here to ensure that we don't try and download remote
         # media multiple times concurrently
         key = (server_name, media_id)
-        with (await self.remote_media_linearizer.queue(key)):
+        async with self.remote_media_linearizer.queue(key):
             responder, media_info = await self._get_remote_media_impl(
                 server_name, media_id
             )
@@ -294,7 +294,7 @@ class MediaRepository:
         # We linearize here to ensure that we don't try and download remote
         # media multiple times concurrently
         key = (server_name, media_id)
-        with (await self.remote_media_linearizer.queue(key)):
+        async with self.remote_media_linearizer.queue(key):
             responder, media_info = await self._get_remote_media_impl(
                 server_name, media_id
             )
@@ -850,7 +850,7 @@ class MediaRepository:
 
             # TODO: Should we delete from the backup store
 
-            with (await self.remote_media_linearizer.queue(key)):
+            async with self.remote_media_linearizer.queue(key):
                 full_path = self.filepaths.remote_media_filepath(origin, file_id)
                 try:
                     os.remove(full_path)
diff --git a/synapse/state/__init__.py b/synapse/state/__init__.py
index 21888cc8c5..fbf7ba4600 100644
--- a/synapse/state/__init__.py
+++ b/synapse/state/__init__.py
@@ -573,7 +573,7 @@ class StateResolutionHandler:
         """
         group_names = frozenset(state_groups_ids.keys())
 
-        with (await self.resolve_linearizer.queue(group_names)):
+        async with self.resolve_linearizer.queue(group_names):
             cache = self._state_cache.get(group_names, None)
             if cache:
                 return cache
diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index 98d09b3736..48e83592e7 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -888,7 +888,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             return frozenset(cache.hosts_to_joined_users)
 
         # Since we'll mutate the cache we need to lock.
-        with (await self._joined_host_linearizer.queue(room_id)):
+        async with self._joined_host_linearizer.queue(room_id):
             if state_entry.state_group == cache.state_group:
                 # Same state group, so nothing to do. We've already checked for
                 # this above, but the cache may have changed while waiting on
diff --git a/synapse/util/async_helpers.py b/synapse/util/async_helpers.py
index 6a8e844d63..4b2a16a6a9 100644
--- a/synapse/util/async_helpers.py
+++ b/synapse/util/async_helpers.py
@@ -18,7 +18,7 @@ import collections
 import inspect
 import itertools
 import logging
-from contextlib import asynccontextmanager, contextmanager
+from contextlib import asynccontextmanager
 from typing import (
     Any,
     AsyncIterator,
@@ -29,7 +29,6 @@ from typing import (
     Generic,
     Hashable,
     Iterable,
-    Iterator,
     List,
     Optional,
     Set,
@@ -342,7 +341,7 @@ class Linearizer:
 
     Example:
 
-        with await limiter.queue("test_key"):
+        async with limiter.queue("test_key"):
             # do some work.
 
     """
@@ -383,95 +382,53 @@ class Linearizer:
         # non-empty.
         return bool(entry.deferreds)
 
-    def queue(self, key: Hashable) -> defer.Deferred:
-        # we avoid doing defer.inlineCallbacks here, so that cancellation works correctly.
-        # (https://twistedmatrix.com/trac/ticket/4632 meant that cancellations were not
-        # propagated inside inlineCallbacks until Twisted 18.7)
+    def queue(self, key: Hashable) -> AsyncContextManager[None]:
+        @asynccontextmanager
+        async def _ctx_manager() -> AsyncIterator[None]:
+            entry = await self._acquire_lock(key)
+            try:
+                yield
+            finally:
+                self._release_lock(key, entry)
+
+        return _ctx_manager()
+
+    async def _acquire_lock(self, key: Hashable) -> _LinearizerEntry:
+        """Acquires a linearizer lock, waiting if necessary.
+
+        Returns once we have secured the lock.
+        """
         entry = self.key_to_defer.setdefault(
             key, _LinearizerEntry(0, collections.OrderedDict())
         )
 
-        # If the number of things executing is greater than the maximum
-        # then add a deferred to the list of blocked items
-        # When one of the things currently executing finishes it will callback
-        # this item so that it can continue executing.
-        if entry.count >= self.max_count:
-            res = self._await_lock(key)
-        else:
+        if entry.count < self.max_count:
+            # The number of things executing is less than the maximum.
             logger.debug(
                 "Acquired uncontended linearizer lock %r for key %r", self.name, key
             )
             entry.count += 1
-            res = defer.succeed(None)
-
-        # once we successfully get the lock, we need to return a context manager which
-        # will release the lock.
-
-        @contextmanager
-        def _ctx_manager(_: None) -> Iterator[None]:
-            try:
-                yield
-            finally:
-                logger.debug("Releasing linearizer lock %r for key %r", self.name, key)
-
-                # We've finished executing so check if there are any things
-                # blocked waiting to execute and start one of them
-                entry.count -= 1
-
-                if entry.deferreds:
-                    (next_def, _) = entry.deferreds.popitem(last=False)
-
-                    # we need to run the next thing in the sentinel context.
-                    with PreserveLoggingContext():
-                        next_def.callback(None)
-                elif entry.count == 0:
-                    # We were the last thing for this key: remove it from the
-                    # map.
-                    del self.key_to_defer[key]
-
-        res.addCallback(_ctx_manager)
-        return res
-
-    def _await_lock(self, key: Hashable) -> defer.Deferred:
-        """Helper for queue: adds a deferred to the queue
-
-        Assumes that we've already checked that we've reached the limit of the number
-        of lock-holders we allow. Creates a new deferred which is added to the list, and
-        adds some management around cancellations.
-
-        Returns the deferred, which will callback once we have secured the lock.
-
-        """
-        entry = self.key_to_defer[key]
+            return entry
 
+        # Otherwise, the number of things executing is at the maximum and we have to
+        # add a deferred to the list of blocked items.
+        # When one of the things currently executing finishes it will callback
+        # this item so that it can continue executing.
         logger.debug("Waiting to acquire linearizer lock %r for key %r", self.name, key)
 
         new_defer: "defer.Deferred[None]" = make_deferred_yieldable(defer.Deferred())
         entry.deferreds[new_defer] = 1
 
-        def cb(_r: None) -> "defer.Deferred[None]":
-            logger.debug("Acquired linearizer lock %r for key %r", self.name, key)
-            entry.count += 1
-
-            # if the code holding the lock completes synchronously, then it
-            # will recursively run the next claimant on the list. That can
-            # relatively rapidly lead to stack exhaustion. This is essentially
-            # the same problem as http://twistedmatrix.com/trac/ticket/9304.
-            #
-            # In order to break the cycle, we add a cheeky sleep(0) here to
-            # ensure that we fall back to the reactor between each iteration.
-            #
-            # (This needs to happen while we hold the lock, and the context manager's exit
-            # code must be synchronous, so this is the only sensible place.)
-            return self._clock.sleep(0)
-
-        def eb(e: Failure) -> Failure:
+        try:
+            await new_defer
+        except Exception as e:
             logger.info("defer %r got err %r", new_defer, e)
             if isinstance(e, CancelledError):
                 logger.debug(
-                    "Cancelling wait for linearizer lock %r for key %r", self.name, key
+                    "Cancelling wait for linearizer lock %r for key %r",
+                    self.name,
+                    key,
                 )
-
             else:
                 logger.warning(
                     "Unexpected exception waiting for linearizer lock %r for key %r",
@@ -481,10 +438,43 @@ class Linearizer:
 
             # we just have to take ourselves back out of the queue.
             del entry.deferreds[new_defer]
-            return e
+            raise
+
+        logger.debug("Acquired linearizer lock %r for key %r", self.name, key)
+        entry.count += 1
 
-        new_defer.addCallbacks(cb, eb)
-        return new_defer
+        # if the code holding the lock completes synchronously, then it
+        # will recursively run the next claimant on the list. That can
+        # relatively rapidly lead to stack exhaustion. This is essentially
+        # the same problem as http://twistedmatrix.com/trac/ticket/9304.
+        #
+        # In order to break the cycle, we add a cheeky sleep(0) here to
+        # ensure that we fall back to the reactor between each iteration.
+        #
+        # This needs to happen while we hold the lock. We could put it on the
+        # exit path, but that would slow down the uncontended case.
+        await self._clock.sleep(0)
+
+        return entry
+
+    def _release_lock(self, key: Hashable, entry: _LinearizerEntry) -> None:
+        """Releases a held linearizer lock."""
+        logger.debug("Releasing linearizer lock %r for key %r", self.name, key)
+
+        # We've finished executing so check if there are any things
+        # blocked waiting to execute and start one of them
+        entry.count -= 1
+
+        if entry.deferreds:
+            (next_def, _) = entry.deferreds.popitem(last=False)
+
+            # we need to run the next thing in the sentinel context.
+            with PreserveLoggingContext():
+                next_def.callback(None)
+        elif entry.count == 0:
+            # We were the last thing for this key: remove it from the
+            # map.
+            del self.key_to_defer[key]
 
 
 class ReadWriteLock:
generated by cgit-pink 1.4.1 (git 2.36.1) at 2024-11-22 09:22:20 +0000