trace: fix data race in RenderEvents

marefr · gopherbot · commit ec11eccf5a0f · 2025-11-24T17:04:07.000-08:00
This commit updates the RenderEvents function by moving the read lock for event families so that it happens before checking the length of event families and by that fixing a data race problem. Fixes golang/go#76402 Change-Id: Id02ebaa25cec8ef631aaf928ba084b0692e84583 Reviewed-on: https://go-review.googlesource.com/c/net/+/723160 Auto-Submit: Sean Liao <sean@liao.dev> Reviewed-by: Sean Liao <sean@liao.dev> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Auto-Submit: Damien Neil <dneil@google.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Nicholas Husin <nsh@golang.org> Reviewed-by: Nicholas Husin <husin@google.com>
diff --git a/trace/events.go b/trace/events.go
@@ -58,8 +58,8 @@ func RenderEvents(w http.ResponseWriter, req *http.Request, sensitive bool) {
 		Buckets: buckets,
 	}
 
-	data.Families = make([]string, 0, len(families))
 	famMu.RLock()
+	data.Families = make([]string, 0, len(families))
 	for name := range families {
 		data.Families = append(data.Families, name)
 	}

Original file line number	Diff line number	Diff line change
`@@ -58,8 +58,8 @@ func RenderEvents(w http.ResponseWriter, req *http.Request, sensitive bool) {`
`58`	`58`	`Buckets: buckets,`
`59`	`59`	`}`
`60`	`60`
`61`		`- data.Families = make([]string, 0, len(families))`
`62`	`61`	`famMu.RLock()`
	`62`	`+ data.Families = make([]string, 0, len(families))`
`63`	`63`	`for name := range families {`
`64`	`64`	`data.Families = append(data.Families, name)`
`65`	`65`	`}`