Use a separate context when updating the NSC (#16209)

There is a race condition introduced in #16149 in which the update to
the NSC happens with a context that may be cancelled by the time the
routine is called. This PR starts a new context with a deadline to call
the routine in the background.

fixes #16205

beacon-chain/blockchain/process_block.go

@@ -106,7 +106,12 @@ func (s *Service) postBlockProcess(cfg *postBlockProcessConfig) error {
 
 	// Pre-Fulu the caches are updated when computing the payload attributes
 	if cfg.postState.Version() >= version.Fulu {
-		go s.updateCachesPostBlockProcessing(cfg)
+		go func() {
+			ctx, cancel := context.WithTimeout(s.ctx, slotDeadline)
+			defer cancel()
+			cfg.ctx = ctx
+			s.updateCachesPostBlockProcessing(cfg)
+		}()
 	}
 	return nil
 }
@@ -929,6 +934,8 @@ func (s *Service) lateBlockTasks(ctx context.Context) {
 		// After Fulu, we can update the caches asynchronously after sending FCU to the engine
 		defer func() {
 			go func() {
+				ctx, cancel := context.WithTimeout(s.ctx, slotDeadline)
+				defer cancel()
 				lastState.CopyAllTries()
 				if err := transition.UpdateNextSlotCache(ctx, lastRoot, lastState); err != nil {
 					log.WithError(err).Debug("Could not update next slot state cache")

changelog/potuz_fcu_ctx.md

@@ -0,0 +1,2 @@
+### Changed
+- Use a separate context when updating the slot cache.