netsync: Rename event handler to stall handler.

This renames the event handler goroutine to stallHandler to more
accurately reflect its only remaining purpose after all of the recent
changes to move everything else out of the event handler.

This is a part of the overall effort to convert the code related to
handling the various sync manager events to synchronous code that runs
in the various caller goroutines.

Author: davecgh

internal/netsync/manager.go

@@ -1991,13 +1991,11 @@ func limitAdd(m map[chainhash.Hash]struct{}, hash chainhash.Hash, limit int) {
 	m[hash] = struct{}{}
 }
 
-// eventHandler is the main handler for the sync manager.  It must be run as a
-// goroutine.  It processes block and inv messages in a separate goroutine from
-// the peer handlers so the block (MsgBlock) messages are handled by a single
-// thread without needing to lock memory data structures.  This is important
-// because the sync manager controls which blocks are needed and how the
-// fetching should proceed.
-func (m *SyncManager) eventHandler(ctx context.Context) {
+// stallHandler monitors the header sync process to detect stalls and disconnect
+// the sync peer which ensures clean recovery from stalls.
+//
+// It must be run as a goroutine.
+func (m *SyncManager) stallHandler(ctx context.Context) {
 out:
 	for {
 		select {
@@ -2017,7 +2015,7 @@ out:
 		}
 	}
 
-	log.Trace("Sync manager event handler done")
+	log.Trace("Sync manager stall handler done")
 }
 
 // SyncPeerID returns the ID of the current sync peer, or 0 if there is none.
@@ -2232,11 +2230,11 @@ func (m *SyncManager) IsCurrent() bool {
 func (m *SyncManager) Run(ctx context.Context) {
 	log.Trace("Starting sync manager")
 
-	// Start the event handler goroutine.
+	// Start the stall handler goroutine.
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
-		m.eventHandler(ctx)
+		m.stallHandler(ctx)
 		wg.Done()
 	}()