Simplify APF promise to what is really used in the code

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise/interface.go

@@ -16,14 +16,10 @@ limitations under the License.
 
 package promise
 
-// This file defines interfaces for promises and futures and related
-// things.  These are about coordination among multiple goroutines and
-// so are safe for concurrent calls --- although moderated in some
-// cases by a requirement that the caller hold a certain lock.
-
 // WriteOnce represents a variable that is initially not set and can
 // be set once and is readable.  This is the common meaning for
 // "promise".
+// The implementations of this interface are NOT thread-safe.
 type WriteOnce interface {
 	// Get reads the current value of this variable.  If this variable
 	// is not set yet then this call blocks until this variable gets a
@@ -41,27 +37,3 @@ type WriteOnce interface {
 	// variable's value.
 	Set(interface{}) bool
 }
-
-// LockingWriteOnce is a WriteOnce whose implementation is protected
-// by a lock.
-type LockingWriteOnce interface {
-	WriteOnce
-
-	// GetLocked is like Get but the caller must already hold the
-	// lock.  GetLocked may release, and later re-acquire, the lock
-	// any number of times.  Get may acquire, and later release, the
-	// lock any number of times.
-	GetLocked() interface{}
-
-	// IsSetLocked is like IsSet but the caller must already hold the
-	// lock.  IsSetLocked may release, and later re-acquire, the lock
-	// any number of times.  IsSet may acquire, and later release, the
-	// lock any number of times.
-	IsSetLocked() bool
-
-	// SetLocked is like Set but the caller must already hold the
-	// lock.  SetLocked may release, and later re-acquire, the lock
-	// any number of times.  Set may acquire, and later release, the
-	// lock any number of times
-	SetLocked(interface{}) bool
-}

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise/promise.go

@@ -14,23 +14,21 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package lockingpromise
+package promise
 
 import (
 	"sync"
 
 	"k8s.io/apiserver/pkg/util/flowcontrol/counter"
-	"k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise"
 )
 
-// lockingPromise implementss the promise.LockingWriteOnce interface.
+// promise implements the promise.WriteOnce interface.
 // This implementation is based on a condition variable.
 // This implementation tracks active goroutines:
 // the given counter is decremented for a goroutine waiting for this
 // varible to be set and incremented when such a goroutine is
 // unblocked.
-type lockingPromise struct {
+type promise struct {
-	lock          sync.Locker
 	cond          sync.Cond
 	activeCounter counter.GoRoutineCounter // counter of active goroutines
 	waitingCount  int                      // number of goroutines idle due to this being unset
@@ -38,24 +36,17 @@ type lockingPromise struct {
 	value         interface{}
 }
 
-var _ promise.LockingWriteOnce = &lockingPromise{}
+var _ WriteOnce = &promise{}
 
 // NewWriteOnce makes a new promise.LockingWriteOnce
-func NewWriteOnce(lock sync.Locker, activeCounter counter.GoRoutineCounter) promise.LockingWriteOnce {
+func NewWriteOnce(lock sync.Locker, activeCounter counter.GoRoutineCounter) WriteOnce {
-	return &lockingPromise{
+	return &promise{
-		lock:          lock,
 		cond:          *sync.NewCond(lock),
 		activeCounter: activeCounter,
 	}
 }
 
-func (p *lockingPromise) Get() interface{} {
+func (p *promise) Get() interface{} {
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	return p.GetLocked()
-}
-
-func (p *lockingPromise) GetLocked() interface{} {
 	if !p.isSet {
 		p.waitingCount++
 		p.activeCounter.Add(-1)
@@ -64,23 +55,11 @@ func (p *lockingPromise) GetLocked() interface{} {
 	return p.value
 }
 
-func (p *lockingPromise) IsSet() bool {
+func (p *promise) IsSet() bool {
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	return p.IsSetLocked()
-}
-
-func (p *lockingPromise) IsSetLocked() bool {
 	return p.isSet
 }
 
-func (p *lockingPromise) Set(value interface{}) bool {
+func (p *promise) Set(value interface{}) bool {
-	p.lock.Lock()
-	defer p.lock.Unlock()
-	return p.SetLocked(value)
-}
-
-func (p *lockingPromise) SetLocked(value interface{}) bool {
 	if p.isSet {
 		return false
 	}

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise/promise_test.go

@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-package lockingpromise
+package promise
 
 import (
 	"sync"
@@ -34,6 +34,9 @@ func TestLockingWriteOnce(t *testing.T) {
 	var got atomic.Value
 	counter.Add(1)
 	go func() {
+		lock.Lock()
+		defer lock.Unlock()
+
 		got.Store(wr.Get())
 		atomic.AddInt32(&gots, 1)
 		counter.Add(-1)
@@ -43,13 +46,21 @@ func TestLockingWriteOnce(t *testing.T) {
 	if atomic.LoadInt32(&gots) != 0 {
 		t.Error("Get returned before Set")
 	}
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if wr.IsSet() {
 			t.Error("IsSet before Set")
 		}
+	}()
 	aval := &now
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if !wr.Set(aval) {
 			t.Error("Set() returned false")
 		}
+	}()
 	clock.Run(nil)
 	time.Sleep(time.Second)
 	if atomic.LoadInt32(&gots) != 1 {
@@ -58,11 +69,18 @@ func TestLockingWriteOnce(t *testing.T) {
 	if got.Load() != aval {
 		t.Error("Get did not return what was Set")
 	}
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if !wr.IsSet() {
 			t.Error("IsSet()==false after Set")
 		}
+	}()
 	counter.Add(1)
 	go func() {
+		lock.Lock()
+		defer lock.Unlock()
+
 		got.Store(wr.Get())
 		atomic.AddInt32(&gots, 1)
 		counter.Add(-1)
@@ -75,17 +93,29 @@ func TestLockingWriteOnce(t *testing.T) {
 	if got.Load() != aval {
 		t.Error("Second Get did not return what was Set")
 	}
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if !wr.IsSet() {
-		t.Error("IsSet()==false after second Set")
+			t.Error("IsSet()==false after second Get")
 		}
+	}()
 	later := time.Now()
 	bval := &later
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if wr.Set(bval) {
 			t.Error("second Set() returned true")
 		}
+	}()
+	func() {
+		lock.Lock()
+		defer lock.Unlock()
 		if !wr.IsSet() {
 			t.Error("IsSet() returned false after second set")
 		} else if wr.Get() != aval {
 			t.Error("Get() after second Set returned wrong value")
 		}
+	}()
 }

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/queueset.go

@@ -28,7 +28,7 @@ import (
 	"k8s.io/apiserver/pkg/util/flowcontrol/counter"
 	"k8s.io/apiserver/pkg/util/flowcontrol/debug"
 	fq "k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing"
-	"k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise/lockingpromise"
+	"k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise"
 	"k8s.io/apiserver/pkg/util/flowcontrol/metrics"
 	fqrequest "k8s.io/apiserver/pkg/util/flowcontrol/request"
 	"k8s.io/apiserver/pkg/util/shufflesharding"
@@ -356,7 +356,7 @@ func (req *request) wait() (bool, bool) {
 	// Step 4:
 	// The final step is to wait on a decision from
 	// somewhere and then act on it.
-	decisionAny := req.decision.GetLocked()
+	decisionAny := req.decision.Get()
 	qs.syncTimeLocked()
 	decision, isDecision := decisionAny.(requestDecision)
 	if !isDecision {
@@ -453,7 +453,7 @@ func (qs *queueSet) timeoutOldRequestsAndRejectOrEnqueueLocked(ctx context.Conte
 		fsName:            fsName,
 		flowDistinguisher: flowDistinguisher,
 		ctx:               ctx,
-		decision:          lockingpromise.NewWriteOnce(&qs.lock, qs.counter),
+		decision:          promise.NewWriteOnce(&qs.lock, qs.counter),
 		arrivalTime:       qs.clock.Now(),
 		queue:             queue,
 		descr1:            descr1,
@@ -503,7 +503,7 @@ func (qs *queueSet) removeTimedOutRequestsFromQueueLocked(queue *queue, fsName s
 	waitLimit := now.Add(-qs.qCfg.RequestWaitLimit)
 	reqs.Walk(func(req *request) bool {
 		if waitLimit.After(req.arrivalTime) {
-			req.decision.SetLocked(decisionReject)
+			req.decision.Set(decisionReject)
 			timeoutCount++
 			metrics.AddRequestsInQueues(req.ctx, qs.qCfg.Name, req.fsName, -1)
 			req.NoteQueued(false)
@@ -588,13 +588,13 @@ func (qs *queueSet) dispatchSansQueueLocked(ctx context.Context, width *fqreques
 		flowDistinguisher: flowDistinguisher,
 		ctx:               ctx,
 		startTime:         now,
-		decision:          lockingpromise.NewWriteOnce(&qs.lock, qs.counter),
+		decision:          promise.NewWriteOnce(&qs.lock, qs.counter),
 		arrivalTime:       now,
 		descr1:            descr1,
 		descr2:            descr2,
 		width:             *width,
 	}
-	req.decision.SetLocked(decisionExecute)
+	req.decision.Set(decisionExecute)
 	qs.totRequestsExecuting++
 	qs.totSeatsInUse += req.Seats()
 	metrics.AddRequestsExecuting(ctx, qs.qCfg.Name, fsName, 1)
@@ -643,7 +643,7 @@ func (qs *queueSet) dispatchLocked() bool {
 	}
 	// When a request is dequeued for service -> qs.virtualStart += G
 	queue.virtualStart += qs.estimatedServiceTime * float64(request.Seats())
-	request.decision.SetLocked(decisionExecute)
+	request.decision.Set(decisionExecute)
 	return ok
 }
 
@@ -652,12 +652,12 @@ func (qs *queueSet) dispatchLocked() bool {
 func (qs *queueSet) cancelWait(req *request) {
 	qs.lock.Lock()
 	defer qs.lock.Unlock()
-	if req.decision.IsSetLocked() {
+	if req.decision.IsSet() {
 		// The request has already been removed from the queue
 		// and so we consider its wait to be over.
 		return
 	}
-	req.decision.SetLocked(decisionCancel)
+	req.decision.Set(decisionCancel)
 
 	// remove the request from the queue as it has timed out
 	req.removeFromQueueFn()

staging/src/k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset/types.go

@@ -52,7 +52,10 @@ type request struct {
 	// is removed from its queue.  The value will be decisionReject,
 	// decisionCancel, or decisionExecute; decisionTryAnother never
 	// appears here.
-	decision promise.LockingWriteOnce
+	//
+	// The field is NOT thread-safe and should be protected by the
+	// queueset's lock.
+	decision promise.WriteOnce
 
 	// arrivalTime is the real time when the request entered this system
 	arrivalTime time.Time

vendor/modules.txt

@@ -1549,7 +1549,6 @@ k8s.io/apiserver/pkg/util/flowcontrol/counter
 k8s.io/apiserver/pkg/util/flowcontrol/debug
 k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing
 k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise
-k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/promise/lockingpromise
 k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/queueset
 k8s.io/apiserver/pkg/util/flowcontrol/fairqueuing/testing
 k8s.io/apiserver/pkg/util/flowcontrol/format