use local-channel instead of tokio sync channel

this avoids the mutex overhead in tokio

Cargo.lock

@@ -1324,6 +1324,7 @@ dependencies = [
  "lan-mouse-proto",
  "libadwaita",
  "libc",
+ "local-channel",
  "log",
  "serde",
  "serde_json",
@@ -1403,6 +1404,23 @@ version = "0.4.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "78b3ae25bc7c8c38cec158d1f2757ee79e9b3740fbc7ccf0e59e4b08d793fa89"
 
+[[package]]
+name = "local-channel"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6cbc85e69b8df4b8bb8b89ec634e7189099cea8927a276b7384ce5488e53ec8"
+dependencies = [
+ "futures-core",
+ "futures-sink",
+ "local-waker",
+]
+
+[[package]]
+name = "local-waker"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d873d7c67ce09b42110d801813efbc9364414e356be9935700d368351657487"
+
 [[package]]
 name = "lock_api"
 version = "0.4.12"

Cargo.toml

@@ -50,6 +50,7 @@ slab = "0.4.9"
 endi = "1.1.0"
 thiserror = "1.0.61"
 tokio-util = "0.7.11"
+local-channel = "0.1.5"
 
 [target.'cfg(unix)'.dependencies]
 libc = "0.2.148"

src/dns.rs

@@ -1,5 +1,5 @@
+use local_channel::mpsc::Receiver;
 use std::net::IpAddr;
-use tokio::sync::mpsc::Receiver;
 
 use hickory_resolver::{error::ResolveError, TokioAsyncResolver};
 

src/server.rs

@@ -1,5 +1,6 @@
 use capture_task::CaptureRequest;
 use emulation_task::EmulationRequest;
+use local_channel::mpsc::{channel, Sender};
 use log;
 use std::{
     cell::{Cell, RefCell},
@@ -8,15 +9,7 @@ use std::{
     net::{IpAddr, SocketAddr},
     rc::Rc,
 };
-use tokio::{
-    io::ReadHalf,
-    join, signal,
-    sync::{
-        mpsc::{channel, Sender},
-        Notify,
-    },
-    task::JoinHandle,
-};
+use tokio::{io::ReadHalf, join, signal, sync::Notify, task::JoinHandle};
 use tokio_util::sync::CancellationToken;
 
 use crate::{
@@ -130,12 +123,12 @@ impl Server {
             }
         };
 
-        let (capture_tx, capture_rx) = channel(1); /* requests for input capture */
-        let (emulation_tx, emulation_rx) = channel(1); /* emulation requests */
-        let (udp_recv_tx, udp_recv_rx) = channel(1); /* udp receiver */
-        let (udp_send_tx, udp_send_rx) = channel(1); /* udp sender */
-        let (request_tx, mut request_rx) = channel(1); /* frontend requests */
-        let (dns_tx, dns_rx) = channel(1); /* dns requests */
+        let (capture_tx, capture_rx) = channel(); /* requests for input capture */
+        let (emulation_tx, emulation_rx) = channel(); /* emulation requests */
+        let (udp_recv_tx, udp_recv_rx) = channel(); /* udp receiver */
+        let (udp_send_tx, udp_send_rx) = channel(); /* udp sender */
+        let (request_tx, mut request_rx) = channel(); /* frontend requests */
+        let (dns_tx, dns_rx) = channel(); /* dns requests */
 
         // udp task
         let network = network_task::new(self.clone(), udp_recv_tx.clone(), udp_send_rx).await?;
@@ -200,7 +193,7 @@ impl Server {
                         let request = self.pending_dns_requests.borrow_mut().pop_front();
                         request
                     } {
-                        dns_tx.send(request).await.expect("channel closed");
+                        dns_tx.send(request).expect("channel closed");
                     }
                 }
                 _ = self.cancelled() => break,
@@ -213,13 +206,6 @@ impl Server {
 
         log::info!("terminating service");
 
-        assert!(!capture_tx.is_closed());
-        assert!(!emulation_tx.is_closed());
-        assert!(!udp_recv_tx.is_closed());
-        assert!(!udp_send_tx.is_closed());
-        assert!(!request_tx.is_closed());
-        assert!(!dns_tx.is_closed());
-
         self.cancel();
         futures::future::join_all(join_handles).await;
         let _ = join!(capture, dns_task, emulation, network, ping);
@@ -377,8 +363,8 @@ impl Server {
             None => return,
         };
 
-        let _ = capture.send(CaptureRequest::Destroy(handle)).await;
-        let _ = emulate.send(EmulationRequest::Destroy(handle)).await;
+        let _ = capture.send(CaptureRequest::Destroy(handle));
+        let _ = emulate.send(EmulationRequest::Destroy(handle));
         log::debug!("deactivating client {handle} done");
     }
 
@@ -410,10 +396,8 @@ impl Server {
         };
 
         /* notify emulation, capture and frontends */
-        let _ = capture
-            .send(CaptureRequest::Create(handle, pos.into()))
-            .await;
-        let _ = emulate.send(EmulationRequest::Create(handle)).await;
+        let _ = capture.send(CaptureRequest::Create(handle, pos.into()));
+        let _ = emulate.send(EmulationRequest::Create(handle));
         log::debug!("activating client {handle} done");
     }
 
@@ -433,8 +417,8 @@ impl Server {
         };
 
         if active {
-            let _ = capture.send(CaptureRequest::Destroy(handle)).await;
-            let _ = emulate.send(EmulationRequest::Destroy(handle)).await;
+            let _ = capture.send(CaptureRequest::Destroy(handle));
+            let _ = emulate.send(EmulationRequest::Destroy(handle));
         }
     }
 
@@ -517,13 +501,11 @@ impl Server {
         // update state in event input emulator & input capture
         if changed {
             if active {
-                let _ = capture.send(CaptureRequest::Destroy(handle)).await;
-                let _ = emulate.send(EmulationRequest::Destroy(handle)).await;
+                let _ = capture.send(CaptureRequest::Destroy(handle));
+                let _ = emulate.send(EmulationRequest::Destroy(handle));
             }
-            let _ = capture
-                .send(CaptureRequest::Create(handle, pos.into()))
-                .await;
-            let _ = emulate.send(EmulationRequest::Create(handle)).await;
+            let _ = capture.send(CaptureRequest::Create(handle, pos.into()));
+            let _ = emulate.send(EmulationRequest::Create(handle));
         }
     }
 
@@ -595,7 +577,7 @@ async fn listen_frontend(
         let request = frontend::wait_for_request(&mut stream).await;
         match request {
             Ok(request) => {
-                let _ = request_tx.send(request).await;
+                let _ = request_tx.send(request);
             }
             Err(e) => {
                 if let Some(e) = e.downcast_ref::<io::Error>() {

src/server/capture_task.rs

@@ -1,12 +1,9 @@
 use futures::StreamExt;
 use lan_mouse_proto::ProtoEvent;
+use local_channel::mpsc::{Receiver, Sender};
 use std::net::SocketAddr;
 
-use tokio::{
-    process::Command,
-    sync::mpsc::{Receiver, Sender},
-    task::JoinHandle,
-};
+use tokio::{process::Command, task::JoinHandle};
 
 use input_capture::{
     self, CaptureError, CaptureEvent, CaptureHandle, InputCapture, InputCaptureError, Position,
@@ -161,7 +158,7 @@ async fn handle_capture_event(
             /* released capture */
             State::Receiving => ProtoEvent::Leave(0),
         };
-        sender_tx.send((event, addr)).await.expect("sender closed");
+        sender_tx.send((event, addr)).expect("sender closed");
     };
 
     Ok(())

src/server/emulation_task.rs

@@ -1,10 +1,8 @@
+use local_channel::mpsc::{Receiver, Sender};
 use std::net::SocketAddr;
 
 use lan_mouse_proto::ProtoEvent;
-use tokio::{
-    sync::mpsc::{Receiver, Sender},
-    task::JoinHandle,
-};
+use tokio::task::JoinHandle;
 
 use crate::{
     client::{ClientHandle, ClientManager},
@@ -140,7 +138,7 @@ async fn handle_incoming_event(
     match (event, addr) {
         (ProtoEvent::Pong, _) => { /* ignore pong events */ }
         (ProtoEvent::Ping, addr) => {
-            let _ = sender_tx.send((ProtoEvent::Pong, addr)).await;
+            let _ = sender_tx.send((ProtoEvent::Pong, addr));
         }
         (ProtoEvent::Leave(_), _) => emulate.release_keys(handle).await?,
         (ProtoEvent::Ack(_), _) => server.set_state(State::Sending),
@@ -148,7 +146,6 @@ async fn handle_incoming_event(
             server.set_state(State::Receiving);
             sender_tx
                 .send((ProtoEvent::Ack(0), addr))
-                .await
                 .expect("no channel")
         }
         (ProtoEvent::Input(e), _) => {

src/server/network_task.rs

@@ -1,11 +1,8 @@
+use local_channel::mpsc::{Receiver, Sender};
 use std::{io, net::SocketAddr};
 
 use thiserror::Error;
-use tokio::{
-    net::UdpSocket,
-    sync::mpsc::{Receiver, Sender},
-    task::JoinHandle,
-};
+use tokio::{net::UdpSocket, task::JoinHandle};
 
 use super::Server;
 use lan_mouse_proto::{ProtoEvent, ProtocolError};
@@ -65,7 +62,7 @@ async fn udp_receiver(
 ) {
     loop {
         let event = receive_event(socket).await;
-        receiver_tx.send(event).await.expect("channel closed");
+        receiver_tx.send(event).expect("channel closed");
     }
 }
 

src/server/ping_task.rs

@@ -1,7 +1,8 @@
 use std::{net::SocketAddr, time::Duration};
 
 use lan_mouse_proto::ProtoEvent;
-use tokio::{sync::mpsc::Sender, task::JoinHandle};
+use local_channel::mpsc::Sender;
+use tokio::task::JoinHandle;
 
 use crate::client::ClientHandle;
 
@@ -85,7 +86,7 @@ async fn ping_task(
 
             // ping clients
             for addr in ping_addrs {
-                if sender_ch.send((ProtoEvent::Ping, addr)).await.is_err() {
+                if sender_ch.send((ProtoEvent::Ping, addr)).is_err() {
                     break;
                 }
             }
@@ -122,14 +123,14 @@ async fn ping_task(
             if receiving {
                 for h in unresponsive_clients {
                     log::warn!("device not responding, releasing keys!");
-                    let _ = emulate_notify.send(EmulationRequest::ReleaseKeys(h)).await;
+                    let _ = emulate_notify.send(EmulationRequest::ReleaseKeys(h));
                 }
             } else {
                 // release pointer if the active client has not responded
                 if !unresponsive_clients.is_empty() {
                     log::warn!("client not responding, releasing pointer!");
                     server.state.replace(State::Receiving);
-                    let _ = capture_notify.send(CaptureRequest::Release).await;
+                    let _ = capture_notify.send(CaptureRequest::Release);
                 }
             }
         }