runk: Ignore an error when calling kill cmd with --all option

Ignore an error handling that is triggered when the kill command is called
with `--all option` to the stopped container.

High-level container runtimes such as containerd call the kill command with
`--all` option in order to terminate all processes inside the container
even if the container already is stopped. Hence, a low-level runtime
should allow `kill --all` regardless of the container state like runc.

This commit reverts to the previous behavior.

Fixes: #5555

Signed-off-by: Manabu Sugimoto <Manabu.Sugimoto@sony.com>

src/tools/runk/libcontainer/src/container.rs

@@ -83,14 +83,6 @@ impl Container {
     }
 
     pub fn kill(&self, signal: Signal, all: bool) -> Result<()> {
-        if self.state == ContainerState::Stopped {
-            return Err(anyhow!(
-                "container {} can't be killed because it is {:?}",
-                self.status.id,
-                self.state
-            ));
-        }
-
         if all {
             let pids = self.processes()?;
             for pid in pids {
@@ -100,6 +92,16 @@ impl Container {
                 kill(pid, signal)?;
             }
         } else {
+            // If --all option is not specified and the container is stopped,
+            // kill operation generates an error in accordance with the OCI runtime spec.
+            if self.state == ContainerState::Stopped {
+                return Err(anyhow!(
+                    "container {} can't be killed because it is {:?}",
+                    self.status.id,
+                    self.state
+                ));
+            }
+
             let pid = Pid::from_raw(self.status.pid);
             if status::is_process_running(pid)? {
                 kill(pid, signal)?;

src/tools/runk/libcontainer/src/status.rs

@@ -141,7 +141,7 @@ pub fn is_process_running(pid: Pid) -> Result<bool> {
     match kill(pid, None) {
         Err(errno) => {
             if errno != Errno::ESRCH {
-                return Err(anyhow!("no such process"));
+                return Err(anyhow!("failed to kill process {}: {:?}", pid, errno));
             }
             Ok(false)
         }