Bound subprocess draining and routing intervals

README.md

@@ -196,8 +196,9 @@ If `XDG_CONFIG_HOME` is unset or not an absolute path, they are saved under
 `~/.config/bt-intercom/headsets`. Later, run `bt-intercom run --connect` to
 restore them. `--connect` retries disconnected headsets every 30 seconds; omit
 it if another Bluetooth manager keeps them connected. Routing is polled every
-two seconds by default; change that with `--interval SECONDS`. Ctrl-C or SIGTERM
-closes links created by this process. Existing PipeWire links are not modified.
+two seconds by default; change that with `--interval SECONDS` (minimum: 1 second).
+Ctrl-C or SIGTERM closes links created by this process. Existing PipeWire links
+are not modified.
 Shutdown also cancels and joins background workers, including idle headset
 button readers. `--sco-limit N` sets the maximum SCO/eSCO capacity budget per
 controller (default: 1). In `sco-a2dp` transport, it limits simultaneous talkers

man/bt-intercom.1

@@ -50,7 +50,7 @@ the selected group, and Space to toggle headset membership.
 Set the scan duration from 1 through 300 seconds (default: 15).
 .TP
 .BI run " --interval SECONDS"
-Set the routing update interval (default: 2 seconds).
+Set the routing update interval (default: 2 seconds; minimum: 1 second).
 .TP
 .BI run " --sco-limit N"
 Set the maximum simultaneous SCO/eSCO links per Bluetooth controller (default:

src/cli.rs

@@ -73,7 +73,7 @@ pub(crate) enum CliCommand {
 	Run {
 		#[arg(value_parser = parse_address)]
 		addresses: Vec<Address>,
-		/// Routing update interval in seconds.
+		/// Routing update interval in seconds (minimum: 1).
 		#[arg(long, default_value_t = 2.0, value_parser = parse_interval)]
 		interval: f64,
 		/// Reconnect disconnected headsets every 30 seconds.

src/process.rs

@@ -140,6 +140,15 @@ pub(crate) fn command_cancellable(
 		.inspect_err(|error| {
 			log::debug!("{name} stopped after {:?}: {error}", started.elapsed())
 		})?;
+	while !output.is_finished() || !error.is_finished() {
+		if started.elapsed() >= timeout {
+			kill_process_group(&mut child);
+			let _ = output.join();
+			let _ = error.join();
+			return Err(format!("{name} timed out while draining command output"));
+		}
+		thread::sleep(CHILD_POLL_INTERVAL);
+	}
 	let stdout = output
 		.join()
 		.map_err(|_| "stdout reader panicked".to_string())?
@@ -254,4 +263,18 @@ mod tests {
 		);
 		assert!(start.elapsed() < Duration::from_secs(1));
 	}
+
+	#[test]
+	fn exited_child_cannot_leave_descendants_holding_output_pipes() {
+		let start = Instant::now();
+		assert!(
+			command(
+				&["sh", "-c", "sleep 30 & exit 0"],
+				Duration::from_millis(100)
+			)
+			.unwrap_err()
+			.contains("timed out while draining command output")
+		);
+		assert!(start.elapsed() < Duration::from_secs(1));
+	}
 }

src/runtime_config.rs

@@ -20,8 +20,8 @@ pub(crate) fn parse_interval(value: &str) -> Result<f64, String> {
 	if !interval.is_finite() || interval <= 0.0 || interval >= u64::MAX as f64 {
 		return Err("--interval must be a positive finite number".into());
 	}
-	if Duration::from_secs_f64(interval).is_zero() {
-		return Err("--interval must be at least one nanosecond".into());
+	if interval < 1.0 {
+		return Err("--interval must be at least 1 second".into());
 	}
 	Ok(interval)
 }
@@ -369,7 +369,8 @@ mod tests {
 	}
 
 	#[test]
-	fn rejects_intervals_that_round_to_zero() {
-		assert!(parse_interval("0.00000000001").is_err());
+	fn routing_interval_must_be_at_least_one_second() {
+		assert!(parse_interval("0.999").is_err());
+		assert_eq!(parse_interval("1").unwrap(), 1.0);
 	}
 }