ts/executor: replace tokio with smol-like implementation

The threadshare executor was based on a modified version of tokio
which implemented the throttling strategy in the BasicScheduler.
Upstream tokio codebase has significantly diverged from what it
was when the throttling strategy was implemented making it hard
to follow. This means that we can hardly get updates from the
upstream project and when we cherry pick fixes, we can't reflect
the state of the project on our fork's version. As a consequence,
tools such as cargo-deny can't check for RUSTSEC fixes in our fork.

The smol ecosystem makes it quite easy to implement and maintain
a custom async executor. This MR imports the smol parts that
need modifications to comply with the threadshare model and implements
a throttling executor in place of the tokio fork.

Networking tokio specific types are replaced with Async wrappers
in the spirit of [smol-rs/async-io]. Note however that the Async
wrappers needed modifications in order to use the per thread
Reactor model. This means that higher level upstream networking
crates such as [async-net] can not be used with our Async
implementation.

Based on the example benchmark with ts-udpsrc, performances seem on par
with what we achieved using the tokio fork.

Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/issues/118

Related to https://gitlab.freedesktop.org/gstreamer/gst-plugins-rs/-/merge_requests/604

1 files changed, 13 insertions, 14 deletions

diff --git a/generic/threadshare/src/udpsrc/imp.rs b/generic/threadshare/src/udpsrc/imp.rs
index 5a423fa43..6a3158b84 100644
--- a/generic/threadshare/src/udpsrc/imp.rs
+++ b/generic/threadshare/src/udpsrc/imp.rs
@@ -29,14 +29,14 @@ use once_cell::sync::Lazy;
 
 use std::i32;
 use std::io;
-use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, UdpSocket};
 use std::sync::Arc;
 use std::sync::Mutex as StdMutex;
 use std::time::Duration;
 use std::u16;
 
 use crate::runtime::prelude::*;
-use crate::runtime::{Context, PadSrc, PadSrcRef, PadSrcWeak, Task};
+use crate::runtime::{Async, Context, PadSrc, PadSrcRef, PadSrcWeak, Task};
 
 use crate::socket::{wrap_socket, GioSocketWrapper, Socket, SocketError, SocketRead};
 
@@ -83,10 +83,10 @@ impl Default for Settings {
 }
 
 #[derive(Debug)]
-struct UdpReader(tokio::net::UdpSocket);
+struct UdpReader(Async<UdpSocket>);
 
 impl UdpReader {
-    fn new(socket: tokio::net::UdpSocket) -> Self {
+    fn new(socket: Async<UdpSocket>) -> Self {
         UdpReader(socket)
     }
 }
@@ -438,8 +438,6 @@ impl UdpSrc {
             })?;
 
         let socket = if let Some(ref wrapped_socket) = settings_guard.socket {
-            use std::net::UdpSocket;
-
             let socket: UdpSocket;
 
             #[cfg(unix)]
@@ -452,10 +450,10 @@ impl UdpSrc {
             }
 
             let socket = context.enter(|| {
-                tokio::net::UdpSocket::from_std(socket).map_err(|err| {
+                Async::<UdpSocket>::try_from(socket).map_err(|err| {
                     gst::error_msg!(
                         gst::ResourceError::OpenRead,
-                        ["Failed to setup socket for tokio: {}", err]
+                        ["Failed to setup Async socket: {}", err]
                     )
                 })
             })?;
@@ -555,10 +553,10 @@ impl UdpSrc {
             })?;
 
             let socket = context.enter(|| {
-                tokio::net::UdpSocket::from_std(socket.into()).map_err(|err| {
+                Async::<UdpSocket>::try_from(socket).map_err(|err| {
                     gst::error_msg!(
                         gst::ResourceError::OpenRead,
-                        ["Failed to setup socket for tokio: {}", err]
+                        ["Failed to setup Async socket: {}", err]
                     )
                 })
             })?;
@@ -568,7 +566,8 @@ impl UdpSrc {
                 match addr {
                     IpAddr::V4(addr) => {
                         socket
-                            .join_multicast_v4(addr, Ipv4Addr::new(0, 0, 0, 0))
+                            .as_ref()
+                            .join_multicast_v4(&addr, &Ipv4Addr::new(0, 0, 0, 0))
                             .map_err(|err| {
                                 gst::error_msg!(
                                     gst::ResourceError::OpenRead,
@@ -577,7 +576,7 @@ impl UdpSrc {
                             })?;
                     }
                     IpAddr::V6(addr) => {
-                        socket.join_multicast_v6(&addr, 0).map_err(|err| {
+                        socket.as_ref().join_multicast_v6(&addr, 0).map_err(|err| {
                             gst::error_msg!(
                                 gst::ResourceError::OpenRead,
                                 ["Failed to join multicast group: {}", err]
@@ -592,7 +591,7 @@ impl UdpSrc {
             socket
         };
 
-        let port: i32 = socket.local_addr().unwrap().port().into();
+        let port: i32 = socket.as_ref().local_addr().unwrap().port().into();
         let settings = if settings_guard.port != port {
             settings_guard.port = port;
             let settings = settings_guard.clone();
@@ -834,7 +833,7 @@ impl ObjectImpl for UdpSrc {
                 settings.context = value
                     .get::<Option<String>>()
                     .expect("type checked upstream")
-                    .unwrap_or_else(|| "".into());
+                    .unwrap_or_else(|| DEFAULT_CONTEXT.into());
             }
             "context-wait" => {
                 settings.context_wait = Duration::from_millis(