PVF: Minor refactor in workers code (#7012)

* Move version check to `worker_event_loop`

* More minor refactors

- More consistent use of `format_invalid` and `format_internal`.
- Fix a doc error.
- Fix some poorly-named local variables.

polkadot/node/core/pvf/src/execute/worker.rs

@@ -261,6 +261,13 @@ impl Response {
 			Self::InvalidCandidate(format!("{}: {}", ctx, msg))
 		}
 	}
+	fn format_internal(ctx: &'static str, msg: &str) -> Self {
+		if msg.is_empty() {
+			Self::InternalError(ctx.to_string())
+		} else {
+			Self::InternalError(format!("{}: {}", ctx, msg))
+		}
+	}
 }
 
 /// The entrypoint that the spawned execute worker should start with. The `socket_path` specifies
@@ -268,19 +275,8 @@ impl Response {
 /// is checked against the worker version. A mismatch results in immediate worker termination.
 /// `None` is used for tests and in other situations when version check is not necessary.
 pub fn worker_entrypoint(socket_path: &str, node_version: Option<&str>) {
-	worker_event_loop("execute", socket_path, |rt_handle, mut stream| async move {
+	worker_event_loop("execute", socket_path, node_version, |rt_handle, mut stream| async move {
 		let worker_pid = std::process::id();
-		if let Some(version) = node_version {
-			if version != env!("SUBSTRATE_CLI_IMPL_VERSION") {
-				gum::error!(
-					target: LOG_TARGET,
-					%worker_pid,
-					"Node and worker version mismatch, node needs restarting, forcing shutdown",
-				);
-				crate::kill_parent_node_in_emergency();
-				return Err(io::Error::new(io::ErrorKind::Unsupported, "Version mismatch"))
-			}
-		}
 
 		let handshake = recv_handshake(&mut stream).await?;
 		let executor = Arc::new(Executor::new(handshake.executor_params).map_err(|e| {
@@ -301,7 +297,7 @@ pub fn worker_entrypoint(socket_path: &str, node_version: Option<&str>) {
 			let cpu_time_start = ProcessTime::now();
 
 			// Spawn a new thread that runs the CPU time monitor.
-			let thread_fut = rt_handle
+			let cpu_time_monitor_fut = rt_handle
 				.spawn_blocking(move || {
 					cpu_time_monitor_loop(cpu_time_start, execution_timeout, finished_rx)
 				})
@@ -313,14 +309,14 @@ pub fn worker_entrypoint(socket_path: &str, node_version: Option<&str>) {
 				})
 				.fuse();
 
-			pin_mut!(thread_fut);
+			pin_mut!(cpu_time_monitor_fut);
 			pin_mut!(execute_fut);
 
 			let response = select_biased! {
 				// If this future is not selected, the join handle is dropped and the thread will
 				// finish in the background.
-				join_res = thread_fut => {
-					match join_res {
+				cpu_time_monitor_res = cpu_time_monitor_fut => {
+					match cpu_time_monitor_res {
 						Ok(Some(cpu_time_elapsed)) => {
 							// Log if we exceed the timeout and the other thread hasn't finished.
 							gum::warn!(
@@ -333,12 +329,12 @@ pub fn worker_entrypoint(socket_path: &str, node_version: Option<&str>) {
 							Response::TimedOut
 						},
 						Ok(None) => Response::InternalError("error communicating over finished channel".into()),
-						Err(e) => Response::InternalError(format!("{}", e)),
+						Err(e) => Response::format_internal("cpu time monitor thread error", &e.to_string()),
 					}
 				},
 				execute_res = execute_fut => {
 					let _ = finished_tx.send(());
-					execute_res.unwrap_or_else(|e| Response::InternalError(format!("{}", e)))
+					execute_res.unwrap_or_else(|e| Response::format_internal("execute thread error", &e.to_string()))
 				},
 			};
 
@@ -367,7 +363,7 @@ fn validate_using_artifact(
 
 	let result_descriptor = match ValidationResult::decode(&mut &descriptor_bytes[..]) {
 		Err(err) =>
-			return Response::InvalidCandidate(format!("validation result decoding failed: {}", err)),
+			return Response::format_invalid("validation result decoding failed", &err.to_string()),
 		Ok(r) => r,
 	};