feat(init): watchdog: pinger thread PINGs servers (framework answers, no server code), main kills after 5s unanswered -> crash path; not pinged: terminal, pm (handlers wait for user); give-up drains queued ping; spawntest hang check

crates/server-framework/src/lib.rs

@@ -7,4 +7,4 @@ pub mod server;
 
 pub use codec::{Decode, Encode};
 pub use executor::block_on;
-pub use server::{MALFORMED, Server, serve};
+pub use server::{MALFORMED, PING, Server, serve};

crates/server-framework/src/server/mod.rs

@@ -9,6 +9,11 @@ use types::bounded::CapSlot;
 /// tag, so every client decodes it as an error.
 pub const MALFORMED: usize = usize::MAX;
 
+/// Init's watchdog asking whether the server still serves: answered with
+/// the same word by the loop itself, never seen by the server's code. No
+/// protocol uses it either.
+pub const PING: usize = usize::MAX - 1;
+
 pub trait Server {
     type Request: Decode;
     type Response: Encode;
@@ -37,8 +42,9 @@ pub trait Server {
 
     /// Serves `endpoint` until receiving on it fails (it was destroyed or
     /// the capability revoked), then returns why. Every `Call` gets a
-    /// reply, `[MALFORMED, ..]` if it does not decode; a one-way `Send` is
-    /// handled without one; notification signals go to `signal`.
+    /// reply, `[MALFORMED, ..]` if it does not decode, `[PING, ..]` to a
+    /// `PING`; a one-way `Send` is handled without one; notification
+    /// signals go to `signal`.
     fn run(&mut self, endpoint: CapSlot) -> libkos::syscall::Error {
         use libkos::syscall::{Received, receive_msg, reply_recv};
         let mut next = receive_msg(endpoint);
@@ -48,6 +54,7 @@ pub trait Server {
                 Err(e) => return e,
             };
             next = match message {
+                Received::Call { words, .. } if words[0] == PING => reply_recv(endpoint, [PING, 0, 0, 0], None),
                 Received::Call { badge, words, cap } => {
                     let (reply, give) = self.handle_call(badge, words, cap);
                     reply_recv(endpoint, reply, give)