Hold a fatal error on the framebuffer and reboot in five minutes rather than exiting, since init's death drops the kernel's panic screen over the cause

main.go

@@ -457,6 +457,7 @@ func (d *direction) start(wg *sync.WaitGroup, done *atomic.Bool, rxReady *sync.W
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
+			defer holdPanic()
 			w.run(done)
 		}()
 	}
@@ -473,6 +474,7 @@ func (d *direction) start(wg *sync.WaitGroup, done *atomic.Bool, rxReady *sync.W
 		wg.Add(1)
 		go func() {
 			defer wg.Done()
+			defer holdPanic()
 			w.run(done)
 		}()
 	}
@@ -481,6 +483,7 @@ func (d *direction) start(wg *sync.WaitGroup, done *atomic.Bool, rxReady *sync.W
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
+		defer holdPanic()
 		sender.run(done, startTx)
 	}()
 
@@ -488,12 +491,14 @@ func (d *direction) start(wg *sync.WaitGroup, done *atomic.Bool, rxReady *sync.W
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
+		defer holdPanic()
 		receiver.run(done)
 	}()
 
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
+		defer holdPanic()
 		d.poller.run(done, startTx)
 	}()
 }
@@ -536,10 +541,8 @@ func main() {
 	nsPerM := flag.Float64("ns-per-m", 4.85, "mean of both directions, per metre of cable")
 	flag.Parse()
 
-	// Nothing here is recoverable by the time it reaches this point, and as PID 1
-	// a plain exit would panic the kernel anyway with less to show for it.
 	if err := run(*aName, *bName, *nsPerM); err != nil {
-		panic(err)
+		fatal(err)
 	}
 	// A clean return is ctrl-alt-delete, which the kernel hands PID 1 as a
 	// SIGINT. Exiting on it would panic the kernel over the reboot it was asking
@@ -581,7 +584,16 @@ func (s *sampler) run(done *atomic.Bool, startTx <-chan struct{}) {
 	}
 }
 
-func run(aName, bName string, nsPerM float64) error {
+func run(aName, bName string, nsPerM float64) (err error) {
+	defer func() {
+		if p := recover(); p != nil {
+			if os.Getpid() != 1 {
+				panic(p)
+			}
+			err = fmt.Errorf("%v", p)
+		}
+	}()
+
 	if err := reportChecks("BOOT", bootstrap()); err != nil {
 		return err
 	}
@@ -670,6 +682,7 @@ func run(aName, bName string, nsPerM float64) error {
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
+		defer holdPanic()
 		samp.run(&done, startTx)
 	}()
 	// Not gated on startTx: the cycle and the connected verdict are wanted the
@@ -677,6 +690,7 @@ func run(aName, bName string, nsPerM float64) error {
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
+		defer holdPanic()
 		noise.run(&done)
 	}()
 	// Every return from here on stops the workers before the deferred closes
@@ -693,7 +707,17 @@ func run(aName, bName string, nsPerM float64) error {
 		}
 		wg.Wait()
 	}()
-	rxReady.Wait()
+	// A worker that panics before signalling ready would hang a bare Wait.
+	ready := make(chan struct{})
+	go func() {
+		rxReady.Wait()
+		close(ready)
+	}()
+	select {
+	case <-ready:
+	case p := <-fatalCh:
+		return fmt.Errorf("%v", p)
+	}
 
 	sig := make(chan os.Signal, 1)
 	signal.Notify(sig, syscall.SIGINT, syscall.SIGTERM)
@@ -726,6 +750,8 @@ func run(aName, bName string, nsPerM float64) error {
 	stats := &streamTable{cols: intervalCols, headerEvery: 20}
 	for {
 		select {
+		case p := <-fatalCh:
+			return fmt.Errorf("%v", p)
 		case <-sig:
 			return nil
 		case <-space: