internal/uevent: integrate error handling in event loop

There are many subtleties when recovering from errors in the event loop, and coldboot requires internals to drain the receive buffer as synthetic uevents are being arranged.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/uevent/uevent_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 	"time"
 
+	"hakurei.app/fhs"
 	"hakurei.app/internal/uevent"
 )
 
@@ -155,13 +156,23 @@ func TestDialConsume(t *testing.T) {
 	ctx, cancel := context.WithCancel(t.Context())
 	defer cancel()
 
+	consume := func(c *uevent.Conn, ctx context.Context) error {
+		return c.Consume(ctx, fhs.Sys, events, false, func(path string) {
+			t.Log("coldboot visited", path)
+		}, func(err error) bool {
+			t.Log(err)
+			_, ok := err.(uevent.NeedsColdboot)
+			return !ok
+		}, nil)
+	}
+
 	wg.Go(func() {
-		if err = c.Consume(ctx, events); err != context.Canceled {
+		if err = consume(c, ctx); err != context.Canceled {
 			panic(err)
 		}
 	})
 	wg.Go(func() {
-		if err0 = c0.Consume(ctx, events); err0 != context.Canceled {
+		if err0 = consume(c0, ctx); err0 != context.Canceled {
 			panic(err0)
 		}
 	})
@@ -185,11 +196,11 @@ func TestDialConsume(t *testing.T) {
 	exclExit := make(chan struct{})
 	wg.Go(func() {
 		defer func() { exclExit <- struct{}{} }()
-		errs[0] = c.Consume(ctx, events)
+		errs[0] = consume(c, ctx)
 	})
 	wg.Go(func() {
 		defer func() { exclExit <- struct{}{} }()
-		errs[1] = c.Consume(ctx, events)
+		errs[1] = consume(c, ctx)
 	})
 	<-exclExit
 	cancel()