agent: use channel instead of pipe to send exit signal of process

The situation is not a IPC scene, pipe(2) is too heavy.

We have tokio::sync:⌚:channel after tokio has been introduced.
The channel has better performance and easy to use.

Fixes: #1721

Signed-off-by: Tim Zhang <tim@hyper.sh>

src/agent/rustjail/src/container.rs

@@ -908,7 +908,7 @@ impl BaseContainer for LinuxContainer {
             child = child.env(PIDNS_FD, format!("{}", pidns.unwrap()));
         }
 
-        let child = child.spawn()?;
+        child.spawn()?;
 
         unistd::close(crfd)?;
         unistd::close(cwfd)?;
@@ -964,19 +964,6 @@ impl BaseContainer for LinuxContainer {
 
         self.created = SystemTime::now();
 
-        // create the pipes for notify process exited
-        let (exit_pipe_r, exit_pipe_w) = unistd::pipe2(OFlag::O_CLOEXEC)
-            .context("failed to create pipe")
-            .map_err(|e| {
-                let _ = signal::kill(Pid::from_raw(child.id() as i32), Some(Signal::SIGKILL))
-                    .map_err(|e| warn!(logger, "signal::kill creating pipe {:?}", e));
-
-                e
-            })?;
-
-        p.exit_pipe_w = Some(exit_pipe_w);
-        p.exit_pipe_r = Some(exit_pipe_r);
-
         if p.init {
             let spec = self.config.spec.as_mut().unwrap();
             update_namespaces(&self.logger, spec, p.pid)?;

src/agent/rustjail/src/process.rs

@@ -29,7 +29,6 @@ pub enum StreamType {
     Stdin,
     Stdout,
     Stderr,
-    ExitPipeR,
     TermMaster,
     ParentStdin,
     ParentStdout,
@@ -45,8 +44,8 @@ pub struct Process {
     pub stdin: Option<RawFd>,
     pub stdout: Option<RawFd>,
     pub stderr: Option<RawFd>,
-    pub exit_pipe_r: Option<RawFd>,
-    pub exit_pipe_w: Option<RawFd>,
+    pub exit_tx: Option<tokio::sync::watch::Sender<bool>>,
+    pub exit_rx: Option<tokio::sync::watch::Receiver<bool>>,
     pub extra_files: Vec<File>,
     pub term_master: Option<RawFd>,
     pub tty: bool,
@@ -97,14 +96,15 @@ impl Process {
         pipe_size: i32,
     ) -> Result<Self> {
         let logger = logger.new(o!("subsystem" => "process"));
+        let (exit_tx, exit_rx) = tokio::sync::watch::channel(false);
 
         let mut p = Process {
             exec_id: String::from(id),
             stdin: None,
             stdout: None,
             stderr: None,
-            exit_pipe_w: None,
-            exit_pipe_r: None,
+            exit_tx: Some(exit_tx),
+            exit_rx: Some(exit_rx),
             extra_files: Vec::new(),
             tty: ocip.terminal,
             term_master: None,
@@ -152,7 +152,6 @@ impl Process {
             StreamType::Stdin => self.stdin,
             StreamType::Stdout => self.stdout,
             StreamType::Stderr => self.stderr,
-            StreamType::ExitPipeR => self.exit_pipe_r,
             StreamType::TermMaster => self.term_master,
             StreamType::ParentStdin => self.parent_stdin,
             StreamType::ParentStdout => self.parent_stdout,

src/agent/src/rpc.rs

@@ -369,7 +369,6 @@ impl AgentService {
         let s = self.sandbox.clone();
         let mut resp = WaitProcessResponse::new();
         let pid: pid_t;
-        let stream;
 
         let (exit_send, mut exit_recv) = tokio::sync::mpsc::channel(100);
 
@@ -380,22 +379,20 @@ impl AgentService {
             "exec-id" => eid.clone()
         );
 
-        {
+        let exit_rx = {
             let mut sandbox = s.lock().await;
             let p = find_process(&mut sandbox, cid.as_str(), eid.as_str(), false)?;
 
-            stream = p.get_reader(StreamType::ExitPipeR);
-
             p.exit_watchers.push(exit_send);
             pid = p.pid;
-        }
 
-        if stream.is_some() {
-            info!(sl!(), "reading exit pipe");
+            p.exit_rx.clone()
+        };
 
-            let reader = stream.unwrap();
-            let mut content: Vec<u8> = vec![0, 1];
-            let _ = reader.lock().await.read(&mut content).await;
+        if let Some(mut exit_rx) = exit_rx {
+            info!(sl!(), "cid {} eid {} waiting for exit signal", &cid, &eid);
+            while exit_rx.changed().await.is_ok() {}
+            info!(sl!(), "cid {} eid {} received exit signal", &cid, &eid);
         }
 
         let mut sandbox = s.lock().await;
@@ -1550,11 +1547,6 @@ fn cleanup_process(p: &mut Process) -> Result<()> {
         let _ = unistd::close(p.term_master.unwrap())?;
     }
 
-    if p.exit_pipe_r.is_some() {
-        p.close_stream(StreamType::ExitPipeR);
-        let _ = unistd::close(p.exit_pipe_r.unwrap())?;
-    }
-
     p.notify_term_close();
 
     p.parent_stdin = None;

src/agent/src/signal.rs

@@ -55,13 +55,6 @@ async fn handle_sigchild(logger: Logger, sandbox: Arc<Mutex<Sandbox>>) -> Result
             }
 
             let mut p = process.unwrap();
-
-            if p.exit_pipe_w.is_none() {
-                info!(logger, "process exit pipe not set");
-                continue;
-            }
-
-            let pipe_write = p.exit_pipe_w.unwrap();
             let ret: i32;
 
             match wait_status {
@@ -75,7 +68,7 @@ async fn handle_sigchild(logger: Logger, sandbox: Arc<Mutex<Sandbox>>) -> Result
             }
 
             p.exit_code = ret;
-            let _ = unistd::close(pipe_write);
+            let _ = p.exit_tx.take();
 
             info!(logger, "notify term to close");
             // close the socket file to notify readStdio to close terminal specifically