Move activeQ related fields to separate struct in scheduling queue

pkg/scheduler/internal/queue/active_queue.go

@@ -0,0 +1,337 @@
+/*
+Copyright 2024 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package queue
+
+import (
+	"container/list"
+	"fmt"
+	"sync"
+
+	v1 "k8s.io/api/core/v1"
+	"k8s.io/apimachinery/pkg/types"
+	"k8s.io/klog/v2"
+	"k8s.io/kubernetes/pkg/scheduler/framework"
+	"k8s.io/kubernetes/pkg/scheduler/internal/heap"
+	"k8s.io/kubernetes/pkg/scheduler/metrics"
+)
+
+// activeQueuer is a wrapper for activeQ related operations.
+// Its methods, except "unlocked" ones, take the lock inside.
+// Note: be careful when using unlocked() methods.
+// getLock() methods should be used only for unlocked() methods
+// and it is forbidden to call any other activeQueuer's method under this lock.
+type activeQueuer interface {
+	getLock() *sync.RWMutex
+	unlocked() unlockedActiveQueuer
+
+	pop(logger klog.Logger) (*framework.QueuedPodInfo, error)
+	list() []*v1.Pod
+	len() int
+	has(pInfo *framework.QueuedPodInfo) bool
+
+	listInFlightEvents() []interface{}
+	listInFlightPods() []*v1.Pod
+	clusterEventsForPod(logger klog.Logger, pInfo *framework.QueuedPodInfo) ([]*clusterEvent, error)
+	addEventIfPodInFlight(oldPod, newPod *v1.Pod, event framework.ClusterEvent) bool
+	addEventIfAnyInFlight(oldObj, newObj interface{}, event framework.ClusterEvent) bool
+
+	schedulingCycle() int64
+	done(pod types.UID)
+	close()
+	broadcast()
+}
+
+// unlockedActiveQueuer defines activeQ methods that are not protected by the lock itself.
+// getLock() methods should be used to protect these methods.
+type unlockedActiveQueuer interface {
+	Get(pInfo *framework.QueuedPodInfo) (*framework.QueuedPodInfo, bool)
+	Has(pInfo *framework.QueuedPodInfo) bool
+	AddOrUpdate(pInfo *framework.QueuedPodInfo)
+	Delete(pInfo *framework.QueuedPodInfo) error
+}
+
+// activeQueue implements activeQueuer. All of the fields have to be protected using the lock.
+type activeQueue struct {
+	// lock synchronizes all operations related to activeQ.
+	// It protects activeQ, inFlightPods, inFlightEvents, schedulingCycle and closed fields.
+	// Caution: DO NOT take "SchedulingQueue.lock" after taking "lock".
+	// You should always take "SchedulingQueue.lock" first, otherwise the queue could end up in deadlock.
+	// "lock" should not be taken after taking "nLock".
+	// Correct locking order is: SchedulingQueue.lock > lock > nominator.nLock.
+	lock sync.RWMutex
+
+	// activeQ is heap structure that scheduler actively looks at to find pods to
+	// schedule. Head of heap is the highest priority pod.
+	queue *heap.Heap[*framework.QueuedPodInfo]
+
+	// cond is a condition that is notified when the pod is added to activeQ.
+	// It is used with lock.
+	cond sync.Cond
+
+	// inFlightPods holds the UID of all pods which have been popped out for which Done
+	// hasn't been called yet - in other words, all pods that are currently being
+	// processed (being scheduled, in permit, or in the binding cycle).
+	//
+	// The values in the map are the entry of each pod in the inFlightEvents list.
+	// The value of that entry is the *v1.Pod at the time that scheduling of that
+	// pod started, which can be useful for logging or debugging.
+	inFlightPods map[types.UID]*list.Element
+
+	// inFlightEvents holds the events received by the scheduling queue
+	// (entry value is clusterEvent) together with in-flight pods (entry
+	// value is *v1.Pod). Entries get added at the end while the mutex is
+	// locked, so they get serialized.
+	//
+	// The pod entries are added in Pop and used to track which events
+	// occurred after the pod scheduling attempt for that pod started.
+	// They get removed when the scheduling attempt is done, at which
+	// point all events that occurred in the meantime are processed.
+	//
+	// After removal of a pod, events at the start of the list are no
+	// longer needed because all of the other in-flight pods started
+	// later. Those events can be removed.
+	inFlightEvents *list.List
+
+	// schedCycle represents sequence number of scheduling cycle and is incremented
+	// when a pod is popped.
+	schedCycle int64
+
+	// closed indicates that the queue is closed.
+	// It is mainly used to let Pop() exit its control loop while waiting for an item.
+	closed bool
+
+	// isSchedulingQueueHintEnabled indicates whether the feature gate for the scheduling queue is enabled.
+	isSchedulingQueueHintEnabled bool
+}
+
+func newActiveQueue(queue *heap.Heap[*framework.QueuedPodInfo], isSchedulingQueueHintEnabled bool) *activeQueue {
+	aq := &activeQueue{
+		queue:                        queue,
+		inFlightPods:                 make(map[types.UID]*list.Element),
+		inFlightEvents:               list.New(),
+		isSchedulingQueueHintEnabled: isSchedulingQueueHintEnabled,
+	}
+	aq.cond.L = &aq.lock
+
+	return aq
+}
+
+// getLock returns lock of activeQueue. Its methods should be used only to protect the unlocked() methods.
+func (aq *activeQueue) getLock() *sync.RWMutex {
+	return &aq.lock
+}
+
+// unlocked returns queue methods, that are not protected by the lock itself.
+// getLock() methods should be used to protect queue methods.
+func (aq *activeQueue) unlocked() unlockedActiveQueuer {
+	return aq.queue
+}
+
+// pop removes the head of the queue and returns it.
+// It blocks if the queue is empty and waits until a new item is added to the queue.
+// It increments scheduling cycle when a pod is popped.
+func (aq *activeQueue) pop(logger klog.Logger) (*framework.QueuedPodInfo, error) {
+	aq.lock.Lock()
+	defer aq.lock.Unlock()
+	for aq.queue.Len() == 0 {
+		// When the queue is empty, invocation of Pop() is blocked until new item is enqueued.
+		// When Close() is called, the p.closed is set and the condition is broadcast,
+		// which causes this loop to continue and return from the Pop().
+		if aq.closed {
+			logger.V(2).Info("Scheduling queue is closed")
+			return nil, nil
+		}
+		aq.cond.Wait()
+	}
+	pInfo, err := aq.queue.Pop()
+	if err != nil {
+		return nil, err
+	}
+	pInfo.Attempts++
+	aq.schedCycle++
+	// In flight, no concurrent events yet.
+	if aq.isSchedulingQueueHintEnabled {
+		aq.inFlightPods[pInfo.Pod.UID] = aq.inFlightEvents.PushBack(pInfo.Pod)
+	}
+
+	// Update metrics and reset the set of unschedulable plugins for the next attempt.
+	for plugin := range pInfo.UnschedulablePlugins.Union(pInfo.PendingPlugins) {
+		metrics.UnschedulableReason(plugin, pInfo.Pod.Spec.SchedulerName).Dec()
+	}
+	pInfo.UnschedulablePlugins.Clear()
+	pInfo.PendingPlugins.Clear()
+
+	return pInfo, nil
+}
+
+// list returns all pods that are in the queue.
+func (aq *activeQueue) list() []*v1.Pod {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	var result []*v1.Pod
+	for _, pInfo := range aq.queue.List() {
+		result = append(result, pInfo.Pod)
+	}
+	return result
+}
+
+// len returns length of the queue.
+func (aq *activeQueue) len() int {
+	return aq.queue.Len()
+}
+
+// has inform if pInfo exists in the queue.
+func (aq *activeQueue) has(pInfo *framework.QueuedPodInfo) bool {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	return aq.queue.Has(pInfo)
+}
+
+// listInFlightEvents returns all inFlightEvents.
+func (aq *activeQueue) listInFlightEvents() []interface{} {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	var values []interface{}
+	for event := aq.inFlightEvents.Front(); event != nil; event = event.Next() {
+		values = append(values, event.Value)
+	}
+	return values
+}
+
+// listInFlightPods returns all inFlightPods.
+func (aq *activeQueue) listInFlightPods() []*v1.Pod {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	var pods []*v1.Pod
+	for _, obj := range aq.inFlightPods {
+		pods = append(pods, obj.Value.(*v1.Pod))
+	}
+	return pods
+}
+
+// clusterEventsForPod gets all cluster events that have happened during pod for pInfo is being scheduled.
+func (aq *activeQueue) clusterEventsForPod(logger klog.Logger, pInfo *framework.QueuedPodInfo) ([]*clusterEvent, error) {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	logger.V(5).Info("Checking events for in-flight pod", "pod", klog.KObj(pInfo.Pod), "unschedulablePlugins", pInfo.UnschedulablePlugins, "inFlightEventsSize", aq.inFlightEvents.Len(), "inFlightPodsSize", len(aq.inFlightPods))
+
+	// AddUnschedulableIfNotPresent is called with the Pod at the end of scheduling or binding.
+	// So, given pInfo should have been Pop()ed before,
+	// we can assume pInfo must be recorded in inFlightPods and thus inFlightEvents.
+	inFlightPod, ok := aq.inFlightPods[pInfo.Pod.UID]
+	if !ok {
+		return nil, fmt.Errorf("in flight Pod isn't found in the scheduling queue. If you see this error log, it's likely a bug in the scheduler")
+	}
+
+	var events []*clusterEvent
+	for event := inFlightPod.Next(); event != nil; event = event.Next() {
+		e, ok := event.Value.(*clusterEvent)
+		if !ok {
+			// Must be another in-flight Pod (*v1.Pod). Can be ignored.
+			continue
+		}
+		events = append(events, e)
+	}
+	return events, nil
+}
+
+// addEventIfPodInFlight adds clusterEvent to inFlightEvents if the newPod is in inFlightPods.
+// It returns true if pushed the event to the inFlightEvents.
+func (aq *activeQueue) addEventIfPodInFlight(oldPod, newPod *v1.Pod, event framework.ClusterEvent) bool {
+	aq.lock.Lock()
+	defer aq.lock.Unlock()
+
+	_, ok := aq.inFlightPods[newPod.UID]
+	if ok {
+		aq.inFlightEvents.PushBack(&clusterEvent{
+			event:  event,
+			oldObj: oldPod,
+			newObj: newPod,
+		})
+	}
+	return ok
+}
+
+// addEventIfAnyInFlight adds clusterEvent to inFlightEvents if any pod is in inFlightPods.
+// It returns true if pushed the event to the inFlightEvents.
+func (aq *activeQueue) addEventIfAnyInFlight(oldObj, newObj interface{}, event framework.ClusterEvent) bool {
+	aq.lock.Lock()
+	defer aq.lock.Unlock()
+
+	if len(aq.inFlightPods) != 0 {
+		aq.inFlightEvents.PushBack(&clusterEvent{
+			event:  event,
+			oldObj: oldObj,
+			newObj: newObj,
+		})
+		return true
+	}
+	return false
+}
+
+func (aq *activeQueue) schedulingCycle() int64 {
+	aq.lock.RLock()
+	defer aq.lock.RUnlock()
+	return aq.schedCycle
+}
+
+// done must be called for pod returned by Pop. This allows the queue to
+// keep track of which pods are currently being processed.
+func (aq *activeQueue) done(pod types.UID) {
+	aq.lock.Lock()
+	defer aq.lock.Unlock()
+
+	inFlightPod, ok := aq.inFlightPods[pod]
+	if !ok {
+		// This Pod is already done()ed.
+		return
+	}
+	delete(aq.inFlightPods, pod)
+
+	// Remove the pod from the list.
+	aq.inFlightEvents.Remove(inFlightPod)
+
+	// Remove events which are only referred to by this Pod
+	// so that the inFlightEvents list doesn't grow infinitely.
+	// If the pod was at the head of the list, then all
+	// events between it and the next pod are no longer needed
+	// and can be removed.
+	for {
+		e := aq.inFlightEvents.Front()
+		if e == nil {
+			// Empty list.
+			break
+		}
+		if _, ok := e.Value.(*clusterEvent); !ok {
+			// A pod, must stop pruning.
+			break
+		}
+		aq.inFlightEvents.Remove(e)
+	}
+}
+
+// close closes the activeQueue.
+func (aq *activeQueue) close() {
+	aq.lock.Lock()
+	aq.closed = true
+	aq.lock.Unlock()
+}
+
+// broadcast notifies the pop() operation that new pod(s) was added to the activeQueue.
+func (aq *activeQueue) broadcast() {
+	aq.cond.Broadcast()
+}

pkg/scheduler/internal/queue/scheduling_queue.go

@@ -27,7 +27,6 @@ limitations under the License.
 package queue
 
 import (
-	"container/list"
 	"context"
 	"fmt"
 	"math/rand"
@@ -159,8 +158,8 @@ type PriorityQueue struct {
 	clock clock.Clock
 
 	// lock takes precedence and should be taken first,
-	// before any other locks in the queue (activeQLock or nominator.nLock).
-	// Correct locking order is: lock > activeQLock > nominator.nLock.
+	// before any other locks in the queue (activeQueue.lock or nominator.nLock).
+	// Correct locking order is: lock > activeQueue.lock > nominator.nLock.
 	lock sync.RWMutex
 
 	// pod initial backoff duration.
@@ -170,58 +169,12 @@ type PriorityQueue struct {
 	// the maximum time a pod can stay in the unschedulablePods.
 	podMaxInUnschedulablePodsDuration time.Duration
 
-	// cond is a condition that is notified when the pod is added to activeQ.
-	// It is used with activeQLock.
-	cond sync.Cond
-
-	// activeQLock synchronizes all operations related to activeQ.
-	// It protects activeQ, inFlightPods, inFlightEvents, schedulingCycle and closed fields.
-	// Caution: DO NOT take "lock" after taking "activeQLock".
-	// You should always take "lock" first, otherwise the queue could end up in deadlock.
-	// "activeQLock" should not be taken after taking "nLock".
-	// Correct locking order is: lock > activeQLock > nominator.nLock.
-	activeQLock sync.RWMutex
-
-	// inFlightPods holds the UID of all pods which have been popped out for which Done
-	// hasn't been called yet - in other words, all pods that are currently being
-	// processed (being scheduled, in permit, or in the binding cycle).
-	//
-	// The values in the map are the entry of each pod in the inFlightEvents list.
-	// The value of that entry is the *v1.Pod at the time that scheduling of that
-	// pod started, which can be useful for logging or debugging.
-	//
-	// It should be protected by activeQLock.
-	inFlightPods map[types.UID]*list.Element
-
-	// inFlightEvents holds the events received by the scheduling queue
-	// (entry value is clusterEvent) together with in-flight pods (entry
-	// value is *v1.Pod). Entries get added at the end while the mutex is
-	// locked, so they get serialized.
-	//
-	// The pod entries are added in Pop and used to track which events
-	// occurred after the pod scheduling attempt for that pod started.
-	// They get removed when the scheduling attempt is done, at which
-	// point all events that occurred in the meantime are processed.
-	//
-	// After removal of a pod, events at the start of the list are no
-	// longer needed because all of the other in-flight pods started
-	// later. Those events can be removed.
-	//
-	// It should be protected by activeQLock.
-	inFlightEvents *list.List
-
-	// activeQ is heap structure that scheduler actively looks at to find pods to
-	// schedule. Head of heap is the highest priority pod. It should be protected by activeQLock.
-	activeQ *heap.Heap[*framework.QueuedPodInfo]
+	activeQ activeQueuer
 	// podBackoffQ is a heap ordered by backoff expiry. Pods which have completed backoff
 	// are popped from this heap before the scheduler looks at activeQ
 	podBackoffQ *heap.Heap[*framework.QueuedPodInfo]
 	// unschedulablePods holds pods that have been tried and determined unschedulable.
 	unschedulablePods *UnschedulablePods
-	// schedulingCycle represents sequence number of scheduling cycle and is incremented
-	// when a pod is popped.
-	// It should be protected by activeQLock.
-	schedulingCycle int64
 	// moveRequestCycle caches the sequence number of scheduling cycle when we
 	// received a move request. Unschedulable pods in and before this scheduling
 	// cycle will be put back to activeQueue if we were trying to schedule them
@@ -234,11 +187,6 @@ type PriorityQueue struct {
 	// queueingHintMap is keyed with profile name, valued with registered queueing hint functions.
 	queueingHintMap QueueingHintMapPerProfile
 
-	// closed indicates that the queue is closed.
-	// It is mainly used to let Pop() exit its control loop while waiting for an item.
-	// It should be protected by activeQLock.
-	closed bool
-
 	nsLister listersv1.NamespaceLister
 
 	metricsRecorder metrics.MetricAsyncRecorder
@@ -382,24 +330,23 @@ func NewPriorityQueue(
 		opt(&options)
 	}
 
+	isSchedulingQueueHintEnabled := utilfeature.DefaultFeatureGate.Enabled(features.SchedulerQueueingHints)
+
 	pq := &PriorityQueue{
 		clock:                             options.clock,
 		stop:                              make(chan struct{}),
 		podInitialBackoffDuration:         options.podInitialBackoffDuration,
 		podMaxBackoffDuration:             options.podMaxBackoffDuration,
 		podMaxInUnschedulablePodsDuration: options.podMaxInUnschedulablePodsDuration,
-		activeQ:                           heap.NewWithRecorder(podInfoKeyFunc, heap.LessFunc[*framework.QueuedPodInfo](lessFn), metrics.NewActivePodsRecorder()),
+		activeQ:                           newActiveQueue(heap.NewWithRecorder(podInfoKeyFunc, heap.LessFunc[*framework.QueuedPodInfo](lessFn), metrics.NewActivePodsRecorder()), isSchedulingQueueHintEnabled),
 		unschedulablePods:                 newUnschedulablePods(metrics.NewUnschedulablePodsRecorder(), metrics.NewGatedPodsRecorder()),
-		inFlightPods:                      make(map[types.UID]*list.Element),
-		inFlightEvents:                    list.New(),
 		preEnqueuePluginMap:               options.preEnqueuePluginMap,
 		queueingHintMap:                   options.queueingHintMap,
 		metricsRecorder:                   options.metricsRecorder,
 		pluginMetricsSamplePercent:        options.pluginMetricsSamplePercent,
 		moveRequestCycle:                  -1,
-		isSchedulingQueueHintEnabled:      utilfeature.DefaultFeatureGate.Enabled(features.SchedulerQueueingHints),
+		isSchedulingQueueHintEnabled:      isSchedulingQueueHintEnabled,
 	}
-	pq.cond.L = &pq.activeQLock
 	pq.podBackoffQ = heap.NewWithRecorder(podInfoKeyFunc, pq.podsCompareBackoffCompleted, metrics.NewBackoffPodsRecorder())
 	pq.nsLister = informerFactory.Core().V1().Namespaces().Lister()
 	pq.nominator = newPodNominator(options.podLister, pq.nominatedPodsToInfo)
@@ -601,11 +548,11 @@ func (p *PriorityQueue) moveToActiveQ(logger klog.Logger, pInfo *framework.Queue
 	gatedBefore := pInfo.Gated
 	pInfo.Gated = !p.runPreEnqueuePlugins(context.Background(), pInfo)
 
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
+	p.activeQ.getLock().Lock()
+	defer p.activeQ.getLock().Unlock()
 	if pInfo.Gated {
 		// Add the Pod to unschedulablePods if it's not passing PreEnqueuePlugins.
-		if p.activeQ.Has(pInfo) {
+		if p.activeQ.unlocked().Has(pInfo) {
 			return false
 		}
 		if p.podBackoffQ.Has(pInfo) {
@@ -619,7 +566,7 @@ func (p *PriorityQueue) moveToActiveQ(logger klog.Logger, pInfo *framework.Queue
 		pInfo.InitialAttemptTimestamp = &now
 	}
 
-	p.activeQ.AddOrUpdate(pInfo)
+	p.activeQ.unlocked().AddOrUpdate(pInfo)
 
 	p.unschedulablePods.delete(pInfo.Pod, gatedBefore)
 	_ = p.podBackoffQ.Delete(pInfo) // Don't need to react when pInfo is not found.
@@ -640,7 +587,7 @@ func (p *PriorityQueue) Add(logger klog.Logger, pod *v1.Pod) {
 
 	pInfo := p.newQueuedPodInfo(pod)
 	if added := p.moveToActiveQ(logger, pInfo, framework.PodAdd); added {
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 }
 
@@ -657,16 +604,10 @@ func (p *PriorityQueue) Activate(logger klog.Logger, pods map[string]*v1.Pod) {
 	}
 
 	if activated {
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 }
 
-func (p *PriorityQueue) existsInActiveQ(pInfo *framework.QueuedPodInfo) bool {
-	p.activeQLock.RLock()
-	defer p.activeQLock.RUnlock()
-	return p.activeQ.Has(pInfo)
-}
-
 func (p *PriorityQueue) activate(logger klog.Logger, pod *v1.Pod) bool {
 	var pInfo *framework.QueuedPodInfo
 	// Verify if the pod is present in unschedulablePods or backoffQ.
@@ -701,46 +642,13 @@ func (p *PriorityQueue) isPodBackingoff(podInfo *framework.QueuedPodInfo) bool {
 
 // SchedulingCycle returns current scheduling cycle.
 func (p *PriorityQueue) SchedulingCycle() int64 {
-	p.activeQLock.RLock()
-	defer p.activeQLock.RUnlock()
-	return p.schedulingCycle
-}
-
-// clusterEventsSinceElementUnlocked gets all cluster events that have happened during this inFlightPod is being scheduled.
-// Note: this function assumes activeQLock to be locked by the caller.
-func (p *PriorityQueue) clusterEventsSinceElementUnlocked(inFlightPod *list.Element) []*clusterEvent {
-	var events []*clusterEvent
-	for event := inFlightPod.Next(); event != nil; event = event.Next() {
-		e, ok := event.Value.(*clusterEvent)
-		if !ok {
-			// Must be another in-flight Pod (*v1.Pod). Can be ignored.
-			continue
-		}
-		events = append(events, e)
-	}
-	return events
-}
-
-func (p *PriorityQueue) clusterEventsForPod(logger klog.Logger, pInfo *framework.QueuedPodInfo) ([]*clusterEvent, error) {
-	p.activeQLock.RLock()
-	defer p.activeQLock.RUnlock()
-	logger.V(5).Info("Checking events for in-flight pod", "pod", klog.KObj(pInfo.Pod), "unschedulablePlugins", pInfo.UnschedulablePlugins, "inFlightEventsSize", p.inFlightEvents.Len(), "inFlightPodsSize", len(p.inFlightPods))
-
-	// AddUnschedulableIfNotPresent is called with the Pod at the end of scheduling or binding.
-	// So, given pInfo should have been Pop()ed before,
-	// we can assume pInfo must be recorded in inFlightPods and thus inFlightEvents.
-	inFlightPod, ok := p.inFlightPods[pInfo.Pod.UID]
-	if !ok {
-		return nil, fmt.Errorf("in flight Pod isn't found in the scheduling queue. If you see this error log, it's likely a bug in the scheduler")
-	}
-
-	return p.clusterEventsSinceElementUnlocked(inFlightPod), nil
+	return p.activeQ.schedulingCycle()
 }
 
 // determineSchedulingHintForInFlightPod looks at the unschedulable plugins of the given Pod
 // and determines the scheduling hint for this Pod while checking the events that happened during in-flight.
 func (p *PriorityQueue) determineSchedulingHintForInFlightPod(logger klog.Logger, pInfo *framework.QueuedPodInfo) queueingStrategy {
-	events, err := p.clusterEventsForPod(logger, pInfo)
+	events, err := p.activeQ.clusterEventsForPod(logger, pInfo)
 	if err != nil {
 		logger.Error(err, "Error getting cluster events for pod", "pod", klog.KObj(pInfo.Pod))
 		return queueAfterBackoff
@@ -834,7 +742,7 @@ func (p *PriorityQueue) AddUnschedulableIfNotPresent(logger klog.Logger, pInfo *
 		return fmt.Errorf("Pod %v is already present in unschedulable queue", klog.KObj(pod))
 	}
 
-	if p.existsInActiveQ(pInfo) {
+	if p.activeQ.has(pInfo) {
 		return fmt.Errorf("Pod %v is already present in the active queue", klog.KObj(pod))
 	}
 	if p.podBackoffQ.Has(pInfo) {
@@ -864,7 +772,7 @@ func (p *PriorityQueue) AddUnschedulableIfNotPresent(logger klog.Logger, pInfo *
 	logger.V(3).Info("Pod moved to an internal scheduling queue", "pod", klog.KObj(pod), "event", framework.ScheduleAttemptFailure, "queue", queue, "schedulingCycle", podSchedulingCycle, "hint", schedulingHint, "unschedulable plugins", rejectorPlugins)
 	if queue == activeQ {
 		// When the Pod is moved to activeQ, need to let p.cond know so that the Pod will be pop()ed out.
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 
 	return nil
@@ -895,7 +803,7 @@ func (p *PriorityQueue) flushBackoffQCompleted(logger klog.Logger) {
 	}
 
 	if activated {
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 }
 
@@ -925,81 +833,18 @@ func (p *PriorityQueue) flushUnschedulablePodsLeftover(logger klog.Logger) {
 // Note: This method should NOT be locked by the p.lock at any moment,
 // as it would lead to scheduling throughput degradation.
 func (p *PriorityQueue) Pop(logger klog.Logger) (*framework.QueuedPodInfo, error) {
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
-	for p.activeQ.Len() == 0 {
-		// When the queue is empty, invocation of Pop() is blocked until new item is enqueued.
-		// When Close() is called, the p.closed is set and the condition is broadcast,
-		// which causes this loop to continue and return from the Pop().
-		if p.closed {
-			logger.V(2).Info("Scheduling queue is closed")
-			return nil, nil
-		}
-		p.cond.Wait()
-	}
-	pInfo, err := p.activeQ.Pop()
-	if err != nil {
-		return nil, err
-	}
-	pInfo.Attempts++
-	p.schedulingCycle++
-	// In flight, no concurrent events yet.
-	if p.isSchedulingQueueHintEnabled {
-		p.inFlightPods[pInfo.Pod.UID] = p.inFlightEvents.PushBack(pInfo.Pod)
-	}
-
-	// Update metrics and reset the set of unschedulable plugins for the next attempt.
-	for plugin := range pInfo.UnschedulablePlugins.Union(pInfo.PendingPlugins) {
-		metrics.UnschedulableReason(plugin, pInfo.Pod.Spec.SchedulerName).Dec()
-	}
-	pInfo.UnschedulablePlugins.Clear()
-	pInfo.PendingPlugins.Clear()
-
-	return pInfo, nil
+	return p.activeQ.pop(logger)
 }
 
 // Done must be called for pod returned by Pop. This allows the queue to
 // keep track of which pods are currently being processed.
 func (p *PriorityQueue) Done(pod types.UID) {
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
-
-	p.done(pod)
-}
-
-func (p *PriorityQueue) done(pod types.UID) {
 	if !p.isSchedulingQueueHintEnabled {
 		// do nothing if schedulingQueueHint is disabled.
 		// In that case, we don't have inFlightPods and inFlightEvents.
 		return
 	}
-	inFlightPod, ok := p.inFlightPods[pod]
-	if !ok {
-		// This Pod is already done()ed.
-		return
-	}
-	delete(p.inFlightPods, pod)
-
-	// Remove the pod from the list.
-	p.inFlightEvents.Remove(inFlightPod)
-
-	// Remove events which are only referred to by this Pod
-	// so that the inFlightEvents list doesn't grow infinitely.
-	// If the pod was at the head of the list, then all
-	// events between it and the next pod are no longer needed
-	// and can be removed.
-	for {
-		e := p.inFlightEvents.Front()
-		if e == nil {
-			// Empty list.
-			break
-		}
-		if _, ok := e.Value.(*clusterEvent); !ok {
-			// A pod, must stop pruning.
-			break
-		}
-		p.inFlightEvents.Remove(e)
-	}
+	p.activeQ.done(pod)
 }
 
 // isPodUpdated checks if the pod is updated in a way that it may have become
@@ -1022,12 +867,12 @@ func isPodUpdated(oldPod, newPod *v1.Pod) bool {
 }
 
 func (p *PriorityQueue) updateInActiveQueue(logger klog.Logger, oldPod, newPod *v1.Pod, oldPodInfo *framework.QueuedPodInfo) bool {
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
-	if pInfo, exists := p.activeQ.Get(oldPodInfo); exists {
+	p.activeQ.getLock().Lock()
+	defer p.activeQ.getLock().Unlock()
+	if pInfo, exists := p.activeQ.unlocked().Get(oldPodInfo); exists {
 		_ = pInfo.Update(newPod)
 		p.UpdateNominatedPod(logger, oldPod, pInfo.PodInfo)
-		p.activeQ.AddOrUpdate(pInfo)
+		p.activeQ.unlocked().AddOrUpdate(pInfo)
 		return true
 	}
 	return false
@@ -1042,25 +887,15 @@ func (p *PriorityQueue) Update(logger klog.Logger, oldPod, newPod *v1.Pod) {
 	defer p.lock.Unlock()
 
 	if p.isSchedulingQueueHintEnabled {
-		p.activeQLock.Lock()
-		// the inflight pod will be requeued using the latest version from the informer cache, which matches what the event delivers.
-		if _, ok := p.inFlightPods[newPod.UID]; ok {
+		// The inflight pod will be requeued using the latest version from the informer cache, which matches what the event delivers.
+		// Record this update as Pod/Update because
+		// this update may make the Pod schedulable in case it gets rejected and comes back to the queue.
+		// We can clean it up once we change updatePodInSchedulingQueue to call MoveAllToActiveOrBackoffQueue.
+		// See https://github.com/kubernetes/kubernetes/pull/125578#discussion_r1648338033 for more context.
+		if exists := p.activeQ.addEventIfPodInFlight(oldPod, newPod, framework.UnscheduledPodUpdate); exists {
 			logger.V(6).Info("The pod doesn't be queued for now because it's being scheduled and will be queued back if necessary", "pod", klog.KObj(newPod))
-
-			// Record this update as Pod/Update because
-			// this update may make the Pod schedulable in case it gets rejected and comes back to the queue.
-			// We can clean it up once we change updatePodInSchedulingQueue to call MoveAllToActiveOrBackoffQueue.
-			// See https://github.com/kubernetes/kubernetes/pull/125578#discussion_r1648338033 for more context.
-			p.inFlightEvents.PushBack(&clusterEvent{
-				event:  framework.UnscheduledPodUpdate,
-				oldObj: oldPod,
-				newObj: newPod,
-			})
-
-			p.activeQLock.Unlock()
 			return
 		}
-		p.activeQLock.Unlock()
 	}
 
 	if oldPod != nil {
@@ -1098,7 +933,7 @@ func (p *PriorityQueue) Update(logger klog.Logger, oldPod, newPod *v1.Pod) {
 					p.unschedulablePods.delete(pInfo.Pod, gated)
 				}
 				if queue == activeQ {
-					p.cond.Broadcast()
+					p.activeQ.broadcast()
 					break
 				}
 			}
@@ -1113,7 +948,7 @@ func (p *PriorityQueue) Update(logger klog.Logger, oldPod, newPod *v1.Pod) {
 			}
 
 			if added := p.moveToActiveQ(logger, pInfo, framework.BackoffComplete); added {
-				p.cond.Broadcast()
+				p.activeQ.broadcast()
 			}
 			return
 		}
@@ -1125,7 +960,7 @@ func (p *PriorityQueue) Update(logger klog.Logger, oldPod, newPod *v1.Pod) {
 	// If pod is not in any of the queues, we put it in the active queue.
 	pInfo := p.newQueuedPodInfo(newPod)
 	if added := p.moveToActiveQ(logger, pInfo, framework.PodUpdate); added {
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 }
 
@@ -1136,9 +971,9 @@ func (p *PriorityQueue) Delete(pod *v1.Pod) {
 	defer p.lock.Unlock()
 	p.DeleteNominatedPodIfExists(pod)
 	pInfo := newQueuedPodInfoForLookup(pod)
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
-	if err := p.activeQ.Delete(pInfo); err != nil {
+	p.activeQ.getLock().Lock()
+	defer p.activeQ.getLock().Unlock()
+	if err := p.activeQ.unlocked().Delete(pInfo); err != nil {
 		// The item was probably not found in the activeQ.
 		p.podBackoffQ.Delete(pInfo)
 		if pInfo = p.unschedulablePods.get(pod); pInfo != nil {
@@ -1227,7 +1062,7 @@ func (p *PriorityQueue) requeuePodViaQueueingHint(logger klog.Logger, pInfo *fra
 		return activeQ
 	}
 	if pInfo.Gated {
-		// In case the pod is gated, the Pod is pushed back to unschedulable Pods pool in addToActiveQ.
+		// In case the pod is gated, the Pod is pushed back to unschedulable Pods pool in moveToActiveQ.
 		return unschedulablePods
 	}
 
@@ -1279,24 +1114,19 @@ func (p *PriorityQueue) movePodsToActiveOrBackoffQueue(logger klog.Logger, podIn
 		}
 	}
 
-	p.activeQLock.Lock()
-	defer p.activeQLock.Unlock()
-	p.moveRequestCycle = p.schedulingCycle
+	p.moveRequestCycle = p.activeQ.schedulingCycle()
 
-	if p.isSchedulingQueueHintEnabled && len(p.inFlightPods) != 0 {
-		logger.V(5).Info("Event received while pods are in flight", "event", event.Label, "numPods", len(p.inFlightPods))
+	if p.isSchedulingQueueHintEnabled {
 		// AddUnschedulableIfNotPresent might get called for in-flight Pods later, and in
 		// AddUnschedulableIfNotPresent we need to know whether events were
 		// observed while scheduling them.
-		p.inFlightEvents.PushBack(&clusterEvent{
-			event:  event,
-			oldObj: oldObj,
-			newObj: newObj,
-		})
+		if added := p.activeQ.addEventIfAnyInFlight(oldObj, newObj, event); added {
+			logger.V(5).Info("Event received while pods are in flight", "event", event.Label)
+		}
 	}
 
 	if activated {
-		p.cond.Broadcast()
+		p.activeQ.broadcast()
 	}
 }
 
@@ -1328,13 +1158,7 @@ func (p *PriorityQueue) getUnschedulablePodsWithCrossTopologyTerm(logger klog.Lo
 
 // PodsInActiveQ returns all the Pods in the activeQ.
 func (p *PriorityQueue) PodsInActiveQ() []*v1.Pod {
-	p.activeQLock.RLock()
-	defer p.activeQLock.RUnlock()
-	var result []*v1.Pod
-	for _, pInfo := range p.activeQ.List() {
-		result = append(result, pInfo.Pod)
-	}
-	return result
+	return p.activeQ.list()
 }
 
 var pendingPodsSummary = "activeQ:%v; backoffQ:%v; unschedulablePods:%v"
@@ -1345,7 +1169,7 @@ var pendingPodsSummary = "activeQ:%v; backoffQ:%v; unschedulablePods:%v"
 func (p *PriorityQueue) PendingPods() ([]*v1.Pod, string) {
 	p.lock.RLock()
 	defer p.lock.RUnlock()
-	result := p.PodsInActiveQ()
+	result := p.activeQ.list()
 	activeQLen := len(result)
 	for _, pInfo := range p.podBackoffQ.List() {
 		result = append(result, pInfo.Pod)
@@ -1356,12 +1180,12 @@ func (p *PriorityQueue) PendingPods() ([]*v1.Pod, string) {
 	return result, fmt.Sprintf(pendingPodsSummary, activeQLen, p.podBackoffQ.Len(), len(p.unschedulablePods.podInfoMap))
 }
 
-// Note: this function assumes the caller locks p.lock.RLock.
+// Note: this function assumes the caller locks both p.lock.RLock and p.activeQ.getLock().RLock.
 func (p *PriorityQueue) nominatedPodToInfo(np PodRef) *framework.PodInfo {
 	pod := np.ToPod()
 	pInfoLookup := newQueuedPodInfoForLookup(pod)
 
-	queuedPodInfo, exists := p.activeQ.Get(pInfoLookup)
+	queuedPodInfo, exists := p.activeQ.unlocked().Get(pInfoLookup)
 	if exists {
 		return queuedPodInfo.PodInfo
 	}
@@ -1382,8 +1206,8 @@ func (p *PriorityQueue) nominatedPodToInfo(np PodRef) *framework.PodInfo {
 func (p *PriorityQueue) nominatedPodsToInfo(nominatedPods []PodRef) []*framework.PodInfo {
 	p.lock.RLock()
 	defer p.lock.RUnlock()
-	p.activeQLock.RLock()
-	defer p.activeQLock.RUnlock()
+	p.activeQ.getLock().RLock()
+	defer p.activeQ.getLock().RUnlock()
 	pods := make([]*framework.PodInfo, len(nominatedPods))
 	for i, np := range nominatedPods {
 		pods[i] = p.nominatedPodToInfo(np).DeepCopy()
@@ -1396,11 +1220,8 @@ func (p *PriorityQueue) Close() {
 	p.lock.Lock()
 	defer p.lock.Unlock()
 	close(p.stop)
-	p.activeQLock.Lock()
-	// closed field is locked by activeQLock as it is checked in Pop() without p.lock set.
-	p.closed = true
-	p.activeQLock.Unlock()
-	p.cond.Broadcast()
+	p.activeQ.close()
+	p.activeQ.broadcast()
 }
 
 // DeleteNominatedPodIfExists deletes <pod> from nominatedPods.
@@ -1571,10 +1392,10 @@ func (np PodRef) ToPod() *v1.Pod {
 // by their UID and update/delete them.
 type nominator struct {
 	// nLock synchronizes all operations related to nominator.
-	// Caution: DO NOT take ("SchedulingQueue.lock" or "SchedulingQueue.activeQLock") after taking "nLock".
-	// You should always take "SchedulingQueue.lock" and "SchedulingQueue.activeQLock" first,
+	// Caution: DO NOT take ("SchedulingQueue.lock" or "activeQueue.lock") after taking "nLock".
+	// You should always take "SchedulingQueue.lock" and "activeQueue.lock" first,
 	// otherwise the nominator could end up in deadlock.
-	// Correct locking order is: SchedulingQueue.lock > SchedulingQueue.activeQLock > nLock.
+	// Correct locking order is: SchedulingQueue.lock > activeQueue.lock > nLock.
 	nLock sync.RWMutex
 
 	// podLister is used to verify if the given pod is alive.

pkg/scheduler/internal/queue/scheduling_queue_test.go

@@ -17,7 +17,6 @@ limitations under the License.
 package queue
 
 import (
-	"container/list"
 	"context"
 	"fmt"
 	"math"
@@ -172,14 +171,6 @@ func TestPriorityQueue_AddWithReversePriorityLessFunc(t *testing.T) {
 	}
 }
 
-func listToValues(l *list.List) []interface{} {
-	var values []interface{}
-	for e := l.Front(); e != nil; e = e.Next() {
-		values = append(values, e.Value)
-	}
-	return values
-}
-
 func Test_InFlightPods(t *testing.T) {
 	logger, _ := ktesting.NewTestContext(t)
 	pod := st.MakePod().Name("targetpod").UID("pod1").Obj()
@@ -715,8 +706,8 @@ func Test_InFlightPods(t *testing.T) {
 			}
 
 			actualInFlightPods := make(map[types.UID]*v1.Pod)
-			for uid, element := range q.inFlightPods {
-				actualInFlightPods[uid] = element.Value.(*v1.Pod)
+			for _, pod := range q.activeQ.listInFlightPods() {
+				actualInFlightPods[pod.UID] = pod
 			}
 			wantInFlightPods := make(map[types.UID]*v1.Pod)
 			for _, pod := range test.wantInFlightPods {
@@ -733,35 +724,36 @@ func Test_InFlightPods(t *testing.T) {
 				}
 				wantInFlightEvents = append(wantInFlightEvents, value)
 			}
-			if diff := cmp.Diff(wantInFlightEvents, listToValues(q.inFlightEvents), cmp.AllowUnexported(clusterEvent{})); diff != "" {
+			if diff := cmp.Diff(wantInFlightEvents, q.activeQ.listInFlightEvents(), cmp.AllowUnexported(clusterEvent{})); diff != "" {
 				t.Errorf("Unexpected diff in inFlightEvents (-want, +got):\n%s", diff)
 			}
 
 			if test.wantActiveQPodNames != nil {
-				podInfos := q.activeQ.List()
-				if len(podInfos) != len(test.wantActiveQPodNames) {
-					diff := cmp.Diff(test.wantActiveQPodNames, podInfos, cmpopts.SortSlices(func(a, b interface{}) bool {
-						return a.(framework.PodInfo).Pod.Name < b.(framework.PodInfo).Pod.Name
-					}))
-					t.Fatalf("Length of activeQ is not expected. Got %v, want %v.\n%s", len(podInfos), len(test.wantActiveQPodNames), diff)
+				pods := q.activeQ.list()
+				var podNames []string
+				for _, pod := range pods {
+					podNames = append(podNames, pod.Name)
+				}
+				if diff := cmp.Diff(test.wantActiveQPodNames, podNames); diff != "" {
+					t.Fatalf("Unexpected diff of activeQ pod names (-want, +got):\n%s", diff)
 				}
 
 				wantPodNames := sets.New(test.wantActiveQPodNames...)
-				for _, podInfo := range podInfos {
-					podGotFromActiveQ := podInfo.Pod
-					if !wantPodNames.Has(podGotFromActiveQ.Name) {
-						t.Fatalf("Pod %v was not expected to be in the activeQ.", podGotFromActiveQ.Name)
+				for _, pod := range pods {
+					if !wantPodNames.Has(pod.Name) {
+						t.Fatalf("Pod %v was not expected to be in the activeQ.", pod.Name)
 					}
 				}
 			}
 
 			if test.wantBackoffQPodNames != nil {
 				podInfos := q.podBackoffQ.List()
-				if len(podInfos) != len(test.wantBackoffQPodNames) {
-					diff := cmp.Diff(test.wantBackoffQPodNames, podInfos, cmpopts.SortSlices(func(a, b interface{}) bool {
-						return a.(framework.PodInfo).Pod.Name < b.(framework.PodInfo).Pod.Name
-					}))
-					t.Fatalf("Length of backoffQ is not expected. Got %v, want %v.\n%s", len(podInfos), len(test.wantBackoffQPodNames), diff)
+				var podNames []string
+				for _, pInfo := range podInfos {
+					podNames = append(podNames, pInfo.Pod.Name)
+				}
+				if diff := cmp.Diff(test.wantBackoffQPodNames, podNames); diff != "" {
+					t.Fatalf("Unexpected diff of backoffQ pod names (-want, +got):\n%s", diff)
 				}
 
 				wantPodNames := sets.New(test.wantBackoffQPodNames...)
@@ -1073,7 +1065,7 @@ func TestPriorityQueue_Update(t *testing.T) {
 			prepareFunc: func(t *testing.T, logger klog.Logger, q *PriorityQueue) (oldPod, newPod *v1.Pod) {
 				podInfo := q.newQueuedPodInfo(medPriorityPodInfo.Pod)
 				// We need to once add this Pod to activeQ and Pop() it so that this Pod is registered correctly in inFlightPods.
-				q.activeQ.AddOrUpdate(podInfo)
+				q.activeQ.unlocked().AddOrUpdate(podInfo)
 				if p, err := q.Pop(logger); err != nil || p.Pod != medPriorityPodInfo.Pod {
 					t.Errorf("Expected: %v after Pop, but got: %v", medPriorityPodInfo.Pod.Name, p.Pod.Name)
 				}
@@ -1109,7 +1101,7 @@ func TestPriorityQueue_Update(t *testing.T) {
 					pInfo = pInfoFromBackoff
 				}
 
-				if pInfoFromActive, exists := q.activeQ.Get(newQueuedPodInfoForLookup(newPod)); exists {
+				if pInfoFromActive, exists := q.activeQ.unlocked().Get(newQueuedPodInfoForLookup(newPod)); exists {
 					if tt.wantQ != activeQ {
 						t.Errorf("expected pod %s not to be queued to activeQ, but it was", newPod.Name)
 					}
@@ -1204,10 +1196,10 @@ func TestPriorityQueue_Delete(t *testing.T) {
 	q.Update(logger, highPriorityPodInfo.Pod, highPriNominatedPodInfo.Pod)
 	q.Add(logger, unschedulablePodInfo.Pod)
 	q.Delete(highPriNominatedPodInfo.Pod)
-	if !q.activeQ.Has(newQueuedPodInfoForLookup(unschedulablePodInfo.Pod)) {
+	if !q.activeQ.unlocked().Has(newQueuedPodInfoForLookup(unschedulablePodInfo.Pod)) {
 		t.Errorf("Expected %v to be in activeQ.", unschedulablePodInfo.Pod.Name)
 	}
-	if q.activeQ.Has(newQueuedPodInfoForLookup(highPriNominatedPodInfo.Pod)) {
+	if q.activeQ.unlocked().Has(newQueuedPodInfoForLookup(highPriNominatedPodInfo.Pod)) {
 		t.Errorf("Didn't expect %v to be in activeQ.", highPriorityPodInfo.Pod.Name)
 	}
 	if len(q.nominator.nominatedPods) != 1 {
@@ -1263,7 +1255,7 @@ func TestPriorityQueue_Activate(t *testing.T) {
 
 			// Prepare activeQ/unschedulablePods/podBackoffQ according to the table
 			for _, qPodInfo := range tt.qPodInfoInActiveQ {
-				q.activeQ.AddOrUpdate(qPodInfo)
+				q.activeQ.unlocked().AddOrUpdate(qPodInfo)
 			}
 
 			for _, qPodInfo := range tt.qPodInfoInUnschedulablePods {
@@ -1278,13 +1270,13 @@ func TestPriorityQueue_Activate(t *testing.T) {
 			q.Activate(logger, map[string]*v1.Pod{"test_pod": tt.qPodInfoToActivate.PodInfo.Pod})
 
 			// Check the result after activation by the length of activeQ
-			if wantLen := len(tt.want); q.activeQ.Len() != wantLen {
-				t.Errorf("length compare: want %v, got %v", wantLen, q.activeQ.Len())
+			if wantLen := len(tt.want); q.activeQ.len() != wantLen {
+				t.Errorf("length compare: want %v, got %v", wantLen, q.activeQ.len())
 			}
 
 			// Check if the specific pod exists in activeQ
 			for _, want := range tt.want {
-				if !q.activeQ.Has(newQueuedPodInfoForLookup(want.PodInfo.Pod)) {
+				if !q.activeQ.unlocked().Has(newQueuedPodInfoForLookup(want.PodInfo.Pod)) {
 					t.Errorf("podInfo not exist in activeQ: want %v", want.PodInfo.Pod.Name)
 				}
 			}
@@ -1570,7 +1562,7 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueueWithQueueingHint(t *testing.
 			}
 			cl := testingclock.NewFakeClock(now)
 			q := NewTestQueue(ctx, newDefaultQueueSort(), WithQueueingHintMapPerProfile(m), WithClock(cl))
-			q.activeQ.AddOrUpdate(q.newQueuedPodInfo(test.podInfo.Pod))
+			q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(test.podInfo.Pod))
 			if p, err := q.Pop(logger); err != nil || p.Pod != test.podInfo.Pod {
 				t.Errorf("Expected: %v after Pop, but got: %v", test.podInfo.Pod.Name, p.Pod.Name)
 			}
@@ -1587,7 +1579,7 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueueWithQueueingHint(t *testing.
 				t.Fatalf("expected pod to be queued to backoffQ, but it was not")
 			}
 
-			if q.activeQ.Len() == 0 && test.expectedQ == activeQ {
+			if q.activeQ.len() == 0 && test.expectedQ == activeQ {
 				t.Fatalf("expected pod to be queued to activeQ, but it was not")
 			}
 
@@ -1614,12 +1606,12 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	}
 	q := NewTestQueue(ctx, newDefaultQueueSort(), WithClock(c), WithQueueingHintMapPerProfile(m))
 	// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent()s below.
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != unschedulablePodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", unschedulablePodInfo.Pod.Name, p.Pod.Name)
 	}
 	expectInFlightPods(t, q, unschedulablePodInfo.Pod.UID)
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != highPriorityPodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", highPriorityPodInfo.Pod.Name, p.Pod.Name)
 	}
@@ -1635,7 +1627,7 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	expectInFlightPods(t, q)
 	// Construct a Pod, but don't associate its scheduler failure to any plugin
 	hpp1 := clonePod(highPriorityPodInfo.Pod, "hpp1")
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(hpp1))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(hpp1))
 	if p, err := q.Pop(logger); err != nil || p.Pod != hpp1 {
 		t.Errorf("Expected: %v after Pop, but got: %v", hpp1, p.Pod.Name)
 	}
@@ -1648,7 +1640,7 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	expectInFlightPods(t, q)
 	// Construct another Pod, and associate its scheduler failure to plugin "barPlugin".
 	hpp2 := clonePod(highPriorityPodInfo.Pod, "hpp2")
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(hpp2))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(hpp2))
 	if p, err := q.Pop(logger); err != nil || p.Pod != hpp2 {
 		t.Errorf("Expected: %v after Pop, but got: %v", hpp2, p.Pod.Name)
 	}
@@ -1663,8 +1655,8 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	// because of the queueing hint function registered for NodeAdd/fooPlugin.
 	q.MoveAllToActiveOrBackoffQueue(logger, framework.NodeAdd, nil, nil, nil)
 	q.Add(logger, medPriorityPodInfo.Pod)
-	if q.activeQ.Len() != 1 {
-		t.Errorf("Expected 1 item to be in activeQ, but got: %v", q.activeQ.Len())
+	if q.activeQ.len() != 1 {
+		t.Errorf("Expected 1 item to be in activeQ, but got: %v", q.activeQ.len())
 	}
 	// Pop out the medPriorityPodInfo in activeQ.
 	if p, err := q.Pop(logger); err != nil || p.Pod != medPriorityPodInfo.Pod {
@@ -1683,18 +1675,17 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	}
 	expectInFlightPods(t, q, medPriorityPodInfo.Pod.UID)
 
-	q.schedulingCycle++
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != unschedulablePodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", unschedulablePodInfo.Pod.Name, p.Pod.Name)
 	}
 	expectInFlightPods(t, q, medPriorityPodInfo.Pod.UID, unschedulablePodInfo.Pod.UID)
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != highPriorityPodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", highPriorityPodInfo.Pod.Name, p.Pod.Name)
 	}
 	expectInFlightPods(t, q, medPriorityPodInfo.Pod.UID, unschedulablePodInfo.Pod.UID, highPriorityPodInfo.Pod.UID)
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(hpp1))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(hpp1))
 	if p, err := q.Pop(logger); err != nil || p.Pod != hpp1 {
 		t.Errorf("Expected: %v after Pop, but got: %v", hpp1, p.Pod.Name)
 	}
@@ -1734,8 +1725,8 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueue(t *testing.T) {
 	c.Step(q.podInitialBackoffDuration)
 	q.flushBackoffQCompleted(logger) // flush the completed backoffQ to move hpp1 to activeQ.
 	q.MoveAllToActiveOrBackoffQueue(logger, framework.NodeAdd, nil, nil, nil)
-	if q.activeQ.Len() != 4 {
-		t.Errorf("Expected 4 items to be in activeQ, but got: %v", q.activeQ.Len())
+	if q.activeQ.len() != 4 {
+		t.Errorf("Expected 4 items to be in activeQ, but got: %v", q.activeQ.len())
 	}
 	if q.podBackoffQ.Len() != 0 {
 		t.Errorf("Expected 0 item to be in podBackoffQ, but got: %v", q.podBackoffQ.Len())
@@ -1789,8 +1780,8 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueueWithOutQueueingHint(t *testi
 	// This NodeAdd event moves unschedulablePodInfo and highPriorityPodInfo to the backoffQ,
 	// because of the queueing hint function registered for NodeAdd/fooPlugin.
 	q.MoveAllToActiveOrBackoffQueue(logger, framework.NodeAdd, nil, nil, nil)
-	if q.activeQ.Len() != 1 {
-		t.Errorf("Expected 1 item to be in activeQ, but got: %v", q.activeQ.Len())
+	if q.activeQ.len() != 1 {
+		t.Errorf("Expected 1 item to be in activeQ, but got: %v", q.activeQ.len())
 	}
 	// Pop out the medPriorityPodInfo in activeQ.
 	if p, err := q.Pop(logger); err != nil || p.Pod != medPriorityPodInfo.Pod {
@@ -1810,7 +1801,6 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueueWithOutQueueingHint(t *testi
 		}
 	}
 
-	q.schedulingCycle++
 	unschedulableQueuedPodInfo := q.newQueuedPodInfo(unschedulablePodInfo.Pod, "fooPlugin")
 	highPriorityQueuedPodInfo := q.newQueuedPodInfo(highPriorityPodInfo.Pod, "fooPlugin")
 	hpp1QueuedPodInfo := q.newQueuedPodInfo(hpp1)
@@ -1841,8 +1831,8 @@ func TestPriorityQueue_MoveAllToActiveOrBackoffQueueWithOutQueueingHint(t *testi
 	c.Step(q.podInitialBackoffDuration)
 	q.flushBackoffQCompleted(logger) // flush the completed backoffQ to move hpp1 to activeQ.
 	q.MoveAllToActiveOrBackoffQueue(logger, framework.NodeAdd, nil, nil, nil)
-	if q.activeQ.Len() != 4 {
-		t.Errorf("Expected 4 items to be in activeQ, but got: %v", q.activeQ.Len())
+	if q.activeQ.len() != 4 {
+		t.Errorf("Expected 4 items to be in activeQ, but got: %v", q.activeQ.len())
 	}
 	if q.podBackoffQ.Len() != 0 {
 		t.Errorf("Expected 0 item to be in podBackoffQ, but got: %v", q.podBackoffQ.Len())
@@ -1863,16 +1853,17 @@ func clonePod(pod *v1.Pod, newName string) *v1.Pod {
 func expectInFlightPods(t *testing.T, q *PriorityQueue, uids ...types.UID) {
 	t.Helper()
 	var actualUIDs []types.UID
-	for uid := range q.inFlightPods {
-		actualUIDs = append(actualUIDs, uid)
+	for _, pod := range q.activeQ.listInFlightPods() {
+		actualUIDs = append(actualUIDs, pod.UID)
 	}
 	sortUIDs := cmpopts.SortSlices(func(a, b types.UID) bool { return a < b })
 	if diff := cmp.Diff(uids, actualUIDs, sortUIDs); diff != "" {
 		t.Fatalf("Unexpected content of inFlightPods (-want, +have):\n%s", diff)
 	}
 	actualUIDs = nil
-	for e := q.inFlightEvents.Front(); e != nil; e = e.Next() {
-		if pod, ok := e.Value.(*v1.Pod); ok {
+	events := q.activeQ.listInFlightEvents()
+	for _, e := range events {
+		if pod, ok := e.(*v1.Pod); ok {
 			actualUIDs = append(actualUIDs, pod.UID)
 		}
 	}
@@ -1954,7 +1945,7 @@ func TestPriorityQueue_AssignedPodAdded_(t *testing.T) {
 			q := NewTestQueue(ctx, newDefaultQueueSort(), WithClock(c), WithQueueingHintMapPerProfile(m))
 
 			// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent()s below.
-			q.activeQ.AddOrUpdate(q.newQueuedPodInfo(tt.unschedPod))
+			q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(tt.unschedPod))
 			if p, err := q.Pop(logger); err != nil || p.Pod != tt.unschedPod {
 				t.Errorf("Expected: %v after Pop, but got: %v", tt.unschedPod.Name, p.Pod.Name)
 			}
@@ -1969,7 +1960,7 @@ func TestPriorityQueue_AssignedPodAdded_(t *testing.T) {
 
 			q.AssignedPodAdded(logger, tt.updatedAssignedPod)
 
-			if q.activeQ.Has(newQueuedPodInfoForLookup(tt.unschedPod)) != tt.wantToRequeue {
+			if q.activeQ.unlocked().Has(newQueuedPodInfoForLookup(tt.unschedPod)) != tt.wantToRequeue {
 				t.Fatalf("unexpected Pod move: Pod should be requeued: %v. Pod is actually requeued: %v", tt.wantToRequeue, !tt.wantToRequeue)
 			}
 		})
@@ -2069,11 +2060,11 @@ func TestPriorityQueue_PendingPods(t *testing.T) {
 	defer cancel()
 	q := NewTestQueue(ctx, newDefaultQueueSort())
 	// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent()s below.
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(unschedulablePodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != unschedulablePodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", unschedulablePodInfo.Pod.Name, p.Pod.Name)
 	}
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(highPriorityPodInfo.Pod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != highPriorityPodInfo.Pod {
 		t.Errorf("Expected: %v after Pop, but got: %v", highPriorityPodInfo.Pod.Name, p.Pod.Name)
 	}
@@ -2419,7 +2410,7 @@ func TestPodFailedSchedulingMultipleTimesDoesNotBlockNewerPod(t *testing.T) {
 	})
 
 	// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent() below.
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(unschedulablePod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(unschedulablePod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != unschedulablePod {
 		t.Errorf("Expected: %v after Pop, but got: %v", unschedulablePod.Name, p.Pod.Name)
 	}
@@ -2557,11 +2548,11 @@ func TestHighPriorityFlushUnschedulablePodsLeftover(t *testing.T) {
 	})
 
 	// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent()s below.
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(highPod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(highPod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != highPod {
 		t.Errorf("Expected: %v after Pop, but got: %v", highPod.Name, p.Pod.Name)
 	}
-	q.activeQ.AddOrUpdate(q.newQueuedPodInfo(midPod))
+	q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(midPod))
 	if p, err := q.Pop(logger); err != nil || p.Pod != midPod {
 		t.Errorf("Expected: %v after Pop, but got: %v", midPod.Name, p.Pod.Name)
 	}
@@ -2610,7 +2601,7 @@ func TestPriorityQueue_initPodMaxInUnschedulablePodsDuration(t *testing.T) {
 			operations: []operation{
 				addPodUnschedulablePods,
 				addPodUnschedulablePods,
-				flushUnschedulerQ,
+				flushUnscheduledQ,
 			},
 			operands: []*framework.QueuedPodInfo{pInfo1, pInfo2, nil},
 			expected: []*framework.QueuedPodInfo{pInfo2, pInfo1},
@@ -2621,7 +2612,7 @@ func TestPriorityQueue_initPodMaxInUnschedulablePodsDuration(t *testing.T) {
 			operations: []operation{
 				addPodUnschedulablePods,
 				addPodUnschedulablePods,
-				flushUnschedulerQ,
+				flushUnscheduledQ,
 			},
 			operands: []*framework.QueuedPodInfo{pInfo1, pInfo2, nil},
 			expected: []*framework.QueuedPodInfo{pInfo2, pInfo1},
@@ -2650,15 +2641,17 @@ func TestPriorityQueue_initPodMaxInUnschedulablePodsDuration(t *testing.T) {
 			}
 
 			expectedLen := len(test.expected)
-			if queue.activeQ.Len() != expectedLen {
-				t.Fatalf("Expected %v items to be in activeQ, but got: %v", expectedLen, queue.activeQ.Len())
+			if queue.activeQ.len() != expectedLen {
+				t.Fatalf("Expected %v items to be in activeQ, but got: %v", expectedLen, queue.activeQ.len())
 			}
 
 			for i := 0; i < expectedLen; i++ {
-				if pInfo, err := queue.activeQ.Pop(); err != nil {
+				if pInfo, err := queue.activeQ.pop(logger); err != nil {
 					t.Errorf("Error while popping the head of the queue: %v", err)
 				} else {
 					podInfoList = append(podInfoList, pInfo)
+					// Cleanup attempts counter incremented in activeQ.pop()
+					pInfo.Attempts = 0
 				}
 			}
 
@@ -2679,7 +2672,7 @@ var (
 		// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent() below.
 		// UnschedulablePlugins will get cleared by Pop, so make a copy first.
 		unschedulablePlugins := pInfo.UnschedulablePlugins.Clone()
-		queue.activeQ.AddOrUpdate(queue.newQueuedPodInfo(pInfo.Pod))
+		queue.activeQ.unlocked().AddOrUpdate(queue.newQueuedPodInfo(pInfo.Pod))
 		p, err := queue.Pop(logger)
 		if err != nil {
 			t.Fatalf("Unexpected error during Pop: %v", err)
@@ -2695,7 +2688,7 @@ var (
 	}
 	popAndRequeueAsBackoff = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, pInfo *framework.QueuedPodInfo) {
 		// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent() below.
-		queue.activeQ.AddOrUpdate(queue.newQueuedPodInfo(pInfo.Pod))
+		queue.activeQ.unlocked().AddOrUpdate(queue.newQueuedPodInfo(pInfo.Pod))
 		p, err := queue.Pop(logger)
 		if err != nil {
 			t.Fatalf("Unexpected error during Pop: %v", err)
@@ -2709,7 +2702,7 @@ var (
 		}
 	}
 	addPodActiveQ = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, pInfo *framework.QueuedPodInfo) {
-		queue.activeQ.AddOrUpdate(pInfo)
+		queue.activeQ.unlocked().AddOrUpdate(pInfo)
 	}
 	addPodUnschedulablePods = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, pInfo *framework.QueuedPodInfo) {
 		if !pInfo.Gated {
@@ -2744,7 +2737,7 @@ var (
 	moveClockForward = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, _ *framework.QueuedPodInfo) {
 		queue.clock.(*testingclock.FakeClock).Step(2 * time.Second)
 	}
-	flushUnschedulerQ = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, _ *framework.QueuedPodInfo) {
+	flushUnscheduledQ = func(t *testing.T, logger klog.Logger, queue *PriorityQueue, _ *framework.QueuedPodInfo) {
 		queue.clock.(*testingclock.FakeClock).Step(queue.podMaxInUnschedulablePodsDuration)
 		queue.flushUnschedulablePodsLeftover(logger)
 	}
@@ -2817,15 +2810,17 @@ func TestPodTimestamp(t *testing.T) {
 			}
 
 			expectedLen := len(test.expected)
-			if queue.activeQ.Len() != expectedLen {
-				t.Fatalf("Expected %v items to be in activeQ, but got: %v", expectedLen, queue.activeQ.Len())
+			if queue.activeQ.len() != expectedLen {
+				t.Fatalf("Expected %v items to be in activeQ, but got: %v", expectedLen, queue.activeQ.len())
 			}
 
 			for i := 0; i < expectedLen; i++ {
-				if pInfo, err := queue.activeQ.Pop(); err != nil {
+				if pInfo, err := queue.activeQ.pop(logger); err != nil {
 					t.Errorf("Error while popping the head of the queue: %v", err)
 				} else {
 					podInfoList = append(podInfoList, pInfo)
+					// Cleanup attempts counter incremented in activeQ.pop()
+					pInfo.Attempts = 0
 				}
 			}
 
@@ -3453,12 +3448,12 @@ func TestMoveAllToActiveOrBackoffQueue_PreEnqueueChecks(t *testing.T) {
 			q := NewTestQueue(ctx, newDefaultQueueSort())
 			for i, podInfo := range tt.podInfos {
 				// To simulate the pod is failed in scheduling in the real world, Pop() the pod from activeQ before AddUnschedulableIfNotPresent() below.
-				q.activeQ.AddOrUpdate(q.newQueuedPodInfo(podInfo.Pod))
+				q.activeQ.unlocked().AddOrUpdate(q.newQueuedPodInfo(podInfo.Pod))
 				if p, err := q.Pop(logger); err != nil || p.Pod != podInfo.Pod {
 					t.Errorf("Expected: %v after Pop, but got: %v", podInfo.Pod.Name, p.Pod.Name)
 				}
 				podInfo.UnschedulablePlugins = sets.New("plugin")
-				err := q.AddUnschedulableIfNotPresent(logger, podInfo, q.schedulingCycle)
+				err := q.AddUnschedulableIfNotPresent(logger, podInfo, q.activeQ.schedulingCycle())
 				if err != nil {
 					t.Fatalf("unexpected error from AddUnschedulableIfNotPresent: %v", err)
 				}