[v10.0.x] Plugins: Correct the usage of mutex for gRPC plugin implementation (#68609)

Plugins: Correct the usage of mutex for gRPC plugin implementation (#68555)

correct usage of mutex

(cherry picked from commit bb6ec1470d)

Co-authored-by: Will Browne <wbrowne@users.noreply.github.com>

pkg/plugins/backendplugin/grpcplugin/grpc_plugin.go

@@ -52,7 +52,7 @@ func (p *grpcPlugin) Logger() log.Logger {
 	return p.logger
 }
 
-func (p *grpcPlugin) Start(ctx context.Context) error {
+func (p *grpcPlugin) Start(_ context.Context) error {
 	p.mutex.Lock()
 	defer p.mutex.Unlock()
 
@@ -85,7 +85,7 @@ func (p *grpcPlugin) Start(ctx context.Context) error {
 	return nil
 }
 
-func (p *grpcPlugin) Stop(ctx context.Context) error {
+func (p *grpcPlugin) Stop(_ context.Context) error {
 	p.mutex.Lock()
 	defer p.mutex.Unlock()
 
@@ -109,8 +109,8 @@ func (p *grpcPlugin) Exited() bool {
 }
 
 func (p *grpcPlugin) Decommission() error {
-	p.mutex.RLock()
-	defer p.mutex.RUnlock()
+	p.mutex.Lock()
+	defer p.mutex.Unlock()
 
 	p.decommissioned = true
 
@@ -118,6 +118,8 @@ func (p *grpcPlugin) Decommission() error {
 }
 
 func (p *grpcPlugin) IsDecommissioned() bool {
+	p.mutex.RLock()
+	defer p.mutex.RUnlock()
 	return p.decommissioned
 }