Add comments regarding failpointsMu and panicMu

Signed-off-by: Chun-Hung Tseng <henrybear327@gmail.com>
Co-authored-by: Marek Siarkowicz <marek.siarkowicz@protonmail.com>

runtime/http.go

@@ -38,7 +38,9 @@ func serve(host string) error {
 
 func (*httpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	// Ensures the server(runtime) doesn't panic due to the execution of
-	// panic failpoints during processing of the HTTP request
+	// panic failpoints during processing of the HTTP request, as the
+	// sender of the HTTP request should not be affected by the execution
+	// of the panic failpoints and crash as a side effect
 	panicMu.Lock()
 	defer panicMu.Unlock()
 

runtime/runtime.go

@@ -25,11 +25,17 @@ var (
 	ErrNoExist  = fmt.Errorf("failpoint: failpoint does not exist")
 	ErrDisabled = fmt.Errorf("failpoint: failpoint is disabled")
 
-	failpoints   map[string]*Failpoint
+	failpoints map[string]*Failpoint
+	// failpointsMu protects the failpoints map, preventing concurrent
+	// accesses during commands such as Enabling and Disabling
 	failpointsMu sync.RWMutex
 
 	envTerms map[string]string
 
+	// panicMu (panic mutex) ensures that the action of panic failpoints
+	// and serving of the HTTP requests won't be executed at the same time,
+	// avoiding the possibility that the server runtime panics during processing
+	// requests
 	panicMu sync.Mutex
 )