From 0ea90952bdac100bde3149fa2a7818ba7af943b4 Mon Sep 17 00:00:00 2001
From: Aleksandr Nogikh <nogikh@google.com>
Date: Fri, 22 Mar 2024 17:00:10 +0100
Subject: pkg/fuzzer: remove async priority queue operations

We don't need them.
---
 pkg/fuzzer/prio_queue.go      | 29 ++++++++---------------------
 pkg/fuzzer/prio_queue_test.go | 43 ++++++++++++++++++++++++++++---------------
 2 files changed, 36 insertions(+), 36 deletions(-)

(limited to 'pkg/fuzzer')

diff --git a/pkg/fuzzer/prio_queue.go b/pkg/fuzzer/prio_queue.go
index ea8f448c9..cb35cebf7 100644
--- a/pkg/fuzzer/prio_queue.go
+++ b/pkg/fuzzer/prio_queue.go
@@ -24,41 +24,28 @@ func (p priority) greaterThan(other priority) bool {
 
 type priorityQueue[T any] struct {
 	impl priorityQueueImpl[T]
-	c    *sync.Cond
+	mu   sync.RWMutex
 }
 
 func makePriorityQueue[T any]() *priorityQueue[T] {
-	return &priorityQueue[T]{
-		c: sync.NewCond(&sync.Mutex{}),
-	}
+	return &priorityQueue[T]{}
 }
 
 func (pq *priorityQueue[T]) Len() int {
-	pq.c.L.Lock()
-	defer pq.c.L.Unlock()
+	pq.mu.RLock()
+	defer pq.mu.RUnlock()
 	return pq.impl.Len()
 }
 
 func (pq *priorityQueue[T]) push(item *priorityQueueItem[T]) {
-	pq.c.L.Lock()
-	defer pq.c.L.Unlock()
+	pq.mu.Lock()
+	defer pq.mu.Unlock()
 	heap.Push(&pq.impl, item)
-	pq.c.Signal()
-}
-
-// pop() blocks until there's input.
-func (pq *priorityQueue[T]) pop() *priorityQueueItem[T] {
-	pq.c.L.Lock()
-	defer pq.c.L.Unlock()
-	for pq.impl.Len() == 0 {
-		pq.c.Wait()
-	}
-	return heap.Pop(&pq.impl).(*priorityQueueItem[T])
 }
 
 func (pq *priorityQueue[T]) tryPop() *priorityQueueItem[T] {
-	pq.c.L.Lock()
-	defer pq.c.L.Unlock()
+	pq.mu.Lock()
+	defer pq.mu.Unlock()
 	if len(pq.impl) == 0 {
 		return nil
 	}
diff --git a/pkg/fuzzer/prio_queue_test.go b/pkg/fuzzer/prio_queue_test.go
index b2abdb01b..df8b4e9b0 100644
--- a/pkg/fuzzer/prio_queue_test.go
+++ b/pkg/fuzzer/prio_queue_test.go
@@ -4,10 +4,10 @@
 package fuzzer
 
 import (
-	"sync"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
+	"golang.org/x/sync/errgroup"
 )
 
 func TestPriority(t *testing.T) {
@@ -18,27 +18,40 @@ func TestPriority(t *testing.T) {
 
 func TestPrioQueueOrder(t *testing.T) {
 	pq := makePriorityQueue[int]()
+	assert.Nil(t, pq.tryPop())
+
 	pq.push(&priorityQueueItem[int]{value: 1, prio: priority{1}})
 	pq.push(&priorityQueueItem[int]{value: 3, prio: priority{3}})
 	pq.push(&priorityQueueItem[int]{value: 2, prio: priority{2}})
 
-	assert.Equal(t, 3, pq.pop().value)
-	assert.Equal(t, 2, pq.pop().value)
-	assert.Equal(t, 1, pq.pop().value)
+	assert.Equal(t, 3, pq.tryPop().value)
+	assert.Equal(t, 2, pq.tryPop().value)
+	assert.Equal(t, 1, pq.tryPop().value)
 	assert.Nil(t, pq.tryPop())
+	assert.Zero(t, pq.Len())
 }
 
-func TestPrioQueueWait(t *testing.T) {
-	var wg sync.WaitGroup
+func TestPrioQueueRace(t *testing.T) {
+	var eg errgroup.Group
 	pq := makePriorityQueue[int]()
-	assert.Nil(t, pq.tryPop())
-
-	wg.Add(1)
-	go func() {
-		assert.Equal(t, 10, pq.pop().value)
-		wg.Done()
-	}()
 
-	pq.push(&priorityQueueItem[int]{value: 10, prio: priority{1}})
-	wg.Wait()
+	// Two writers.
+	for writer := 0; writer < 2; writer++ {
+		eg.Go(func() error {
+			for i := 0; i < 1000; i++ {
+				pq.push(&priorityQueueItem[int]{value: 10, prio: priority{1}})
+			}
+			return nil
+		})
+	}
+	// Two readers.
+	for reader := 0; reader < 2; reader++ {
+		eg.Go(func() error {
+			for i := 0; i < 1000; i++ {
+				pq.tryPop()
+			}
+			return nil
+		})
+	}
+	eg.Wait()
 }
-- 
cgit mrf-deployment