Fix a data race in TopologyCache

The member variable `cpuRatiosByZone` should be accessed with the lock
acquired as it could be be updated by `SetNodes` concurrently.

Signed-off-by: Quan Tian <qtian@vmware.com>
Co-authored-by: Antonio Ojea <aojea@google.com>

pkg/controller/endpointslice/topologycache/topologycache.go

@@ -270,6 +270,9 @@ func (t *TopologyCache) HasPopulatedHints(serviceKey string) bool {
 // it is not possible to provide allocations that are below the overload
 // threshold, a nil value will be returned.
 func (t *TopologyCache) getAllocations(numEndpoints int) (map[string]Allocation, *EventBuilder) {
+	t.lock.Lock()
+	defer t.lock.Unlock()
+
 	// it is similar to checking !t.sufficientNodeInfo
 	if t.cpuRatiosByZone == nil {
 		return nil, &EventBuilder{
@@ -293,9 +296,6 @@ func (t *TopologyCache) getAllocations(numEndpoints int) (map[string]Allocation,
 		}
 	}
 
-	t.lock.Lock()
-	defer t.lock.Unlock()
-
 	remainingMinEndpoints := numEndpoints
 	minTotal := 0
 	allocations := map[string]Allocation{}