Use a different fix for #21969

src/core/ext/filters/client_channel/client_channel.cc

@@ -878,24 +878,19 @@ class ChannelData::SubchannelWrapper : public SubchannelInterface {
               "chand=%p: destroying subchannel wrapper %p for subchannel %p",
               chand_, this, subchannel_);
     }
-    auto *subchannel_wrapper = this;
-    auto *subchannel = subchannel_;
-    auto *chand = chand_;
-    chand_->work_serializer()->Run([chand, subchannel, subchannel_wrapper]() {
-      chand->subchannel_wrappers_.erase(subchannel_wrapper);
-      auto* subchannel_node = subchannel->channelz_node();
+    chand_->subchannel_wrappers_.erase(this);
+    auto* subchannel_node = subchannel_->channelz_node();
     if (subchannel_node != nullptr) {
-        auto it = chand->subchannel_refcount_map_.find(subchannel);
-        GPR_ASSERT(it != chand->subchannel_refcount_map_.end());
+      auto it = chand_->subchannel_refcount_map_.find(subchannel_);
+      GPR_ASSERT(it != chand_->subchannel_refcount_map_.end());
       --it->second;
       if (it->second == 0) {
-          chand->channelz_node_->RemoveChildSubchannel(subchannel_node->uuid());
-          chand->subchannel_refcount_map_.erase(it);
+        chand_->channelz_node_->RemoveChildSubchannel(subchannel_node->uuid());
+        chand_->subchannel_refcount_map_.erase(it);
       }
     }
-      GRPC_SUBCHANNEL_UNREF(subchannel, "unref from LB");
-      GRPC_CHANNEL_STACK_UNREF(chand->owning_stack_, "SubchannelWrapper");
-    }, DEBUG_LOCATION);
+    GRPC_SUBCHANNEL_UNREF(subchannel_, "unref from LB");
+    GRPC_CHANNEL_STACK_UNREF(chand_->owning_stack_, "SubchannelWrapper");
   }
 
   grpc_connectivity_state CheckConnectivityState() override {
@@ -1016,7 +1011,12 @@ class ChannelData::SubchannelWrapper : public SubchannelInterface {
           parent_(std::move(parent)),
           last_seen_state_(initial_state) {}
 
-    ~WatcherWrapper() { parent_.reset(DEBUG_LOCATION, "WatcherWrapper"); }
+    ~WatcherWrapper() {
+      auto* parent = parent_.release(); /* ref owned by lambda */
+      parent->chand_->work_serializer_->Run(
+          [parent]() { parent->Unref(DEBUG_LOCATION, "WatcherWrapper"); },
+          DEBUG_LOCATION);
+    }
 
     void OnConnectivityStateChange(
         grpc_connectivity_state new_state,