fix exec hang when tx channel is full

Author: ningmingxiao

crates/runc-shim/src/service.rs

@@ -159,6 +159,9 @@ async fn process_exits(
             if let Subject::Pid(pid) = e.subject {
                 debug!("receive exit event: {}", &e);
                 let exit_code = e.exit_code;
+                let containers = containers.clone();
+                let tx = tx.clone();
+                tokio::spawn(async move {                
                 for (_k, cont) in containers.lock().await.iter_mut() {
                     let bundle = cont.bundle.to_string();
                     // pid belongs to container init process
@@ -204,7 +207,7 @@ async fn process_exits(
                             break;
                         }
                     }
-                }
+                }});
             }
         }
         monitor_unsubscribe(s.id).await.unwrap_or_default();

crates/shim/src/asynchronous/monitor.rs

@@ -19,7 +19,7 @@ use std::collections::HashMap;
 use lazy_static::lazy_static;
 use log::error;
 use tokio::sync::{
-    mpsc::{unbounded_channel, UnboundedReceiver, UnboundedSender},
+    mpsc::{channel, Receiver, Sender},
     Mutex,
 };
 
@@ -68,17 +68,17 @@ pub struct Monitor {
 
 pub(crate) struct Subscriber {
     pub(crate) topic: Topic,
-    pub(crate) tx: UnboundedSender<ExitEvent>,
+    pub(crate) tx: Sender<ExitEvent>,
 }
 
 pub struct Subscription {
     pub id: i64,
-    pub rx: UnboundedReceiver<ExitEvent>,
+    pub rx: Receiver<ExitEvent>,
 }
 
 impl Monitor {
     pub fn subscribe(&mut self, topic: Topic) -> Result<Subscription> {
-        let (tx, rx) = unbounded_channel::<ExitEvent>();
+        let (tx, rx) = channel::<ExitEvent>(128);
         let id = self.seq_id;
         self.seq_id += 1;
         let subscriber = Subscriber {
@@ -116,7 +116,7 @@ impl Monitor {
                     .send(ExitEvent {
                         subject: subject.clone(),
                         exit_code,
-                    })
+                    }).await
                     .map_err(other_error!(e, "failed to send exit code"));
                 results.push(res);
             }