Do not use atomics

Signed-off-by: György Krajcsovits <gyorgy.krajcsovits@grafana.com>

prometheus/histogram.go

@@ -1658,7 +1658,7 @@ func addAndResetCounts(hot, cold *histogramCounts) {
 type nativeExemplars struct {
 	sync.Mutex
 
-	ttl       atomic.Int64 // It is a duration, but also used to check concurrently if exemplars are enabled.
+	ttl       time.Duration
 	exemplars []*dto.Exemplar
 }
 
@@ -1676,13 +1676,12 @@ func makeNativeExemplars(exemplars *nativeExemplars, ttl time.Duration, maxCount
 		ttl = -1
 	}
 
-	exemplars.ttl.Store(int64(ttl))
+	exemplars.ttl = ttl
 	exemplars.exemplars = make([]*dto.Exemplar, 0, maxCount)
 }
 
 func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
-	ttl := n.ttl.Load()
-	if ttl == -1 {
+	if n.ttl == -1 {
 		return
 	}
 
@@ -1764,7 +1763,7 @@ func (n *nativeExemplars) addExemplar(e *dto.Exemplar) {
 	// Here, we have the following relationships:
 	// n.exemplars[nIdx-1].Value < e.Value <= n.exemplars[nIdx].Value
 
-	if otIdx != -1 && e.Timestamp.AsTime().Sub(ot) > time.Duration(ttl) {
+	if otIdx != -1 && e.Timestamp.AsTime().Sub(ot) > n.ttl {
 		// If the oldest exemplar has expired, then replace it with the new exemplar.
 		rIdx = otIdx
 	} else {