misc cleanups

- `min` is now builtin
- `RWMutex` captures intent better

src/acceptance/assets/app/go_app/go.mod

@@ -25,7 +25,6 @@ require (
 	go.opentelemetry.io/otel/sdk v1.24.0
 	go.opentelemetry.io/otel/trace v1.24.0
 	go.uber.org/zap v1.27.0
-	golang.org/x/exp v0.0.0-20240325151524-a685a6edb6d8
 )
 
 require (
@@ -62,6 +61,7 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	golang.org/x/arch v0.7.0 // indirect
 	golang.org/x/crypto v0.21.0 // indirect
+	golang.org/x/exp v0.0.0-20240325151524-a685a6edb6d8 // indirect
 	golang.org/x/mod v0.16.0 // indirect
 	golang.org/x/net v0.22.0 // indirect
 	golang.org/x/sync v0.6.0 // indirect

src/acceptance/assets/app/go_app/internal/app/cpu.go

@@ -9,7 +9,6 @@ import (
 
 	"github.com/gin-gonic/gin"
 	"github.com/go-logr/logr"
-	"golang.org/x/exp/constraints"
 )
 
 //counterfeiter:generate . CPUWaster
@@ -20,7 +19,7 @@ type CPUWaster interface {
 }
 
 type ConcurrentBusyLoopCPUWaster struct {
-	mu        sync.Mutex
+	mu        sync.RWMutex
 	isRunning bool
 }
 
@@ -98,8 +97,8 @@ func (m *ConcurrentBusyLoopCPUWaster) UseCPU(utilisation uint64, duration time.D
 }
 
 func (m *ConcurrentBusyLoopCPUWaster) IsRunning() bool {
-	m.mu.Lock()
-	defer m.mu.Unlock()
+	m.mu.RLock()
+	defer m.mu.RUnlock()
 	return m.isRunning
 }
 
@@ -114,10 +113,3 @@ func (m *ConcurrentBusyLoopCPUWaster) startTest() {
 	defer m.mu.Unlock()
 	m.isRunning = true
 }
-
-func min[T constraints.Ordered](a, b T) T {
-	if a < b {
-		return a
-	}
-	return b
-}

src/acceptance/assets/app/go_app/internal/app/cpu_test.go

@@ -59,14 +59,14 @@ var _ = Describe("CPU tests", func() {
 		Context("UseCPU", FlakeAttempts(3), func() {
 			DescribeTable("should use cpu",
 				func(utilisation uint64, duration time.Duration) {
-					oldCpu := getTotalCPUUsage("before cpuTest info test")
+					oldCpu := getTotalCPUUsage("before test")
 
-					By("allocating cpu")
+					By("wasting cpu time")
 					cpuWaster := &app.ConcurrentBusyLoopCPUWaster{}
 					cpuWaster.UseCPU(utilisation, duration)
 					Expect(cpuWaster.IsRunning()).To(Equal(true))
 					Eventually(cpuWaster.IsRunning).WithTimeout(duration + time.Second).WithPolling(time.Second).Should(Equal(false))
-					newCpu := getTotalCPUUsage("after cpuTest info test")
+					newCpu := getTotalCPUUsage("after test")
 					expectedCPUUsage := multiplyDurationByPercentage(duration, utilisation)
 					// Give 10% tolerance - but at least 1 second, as this is the internal resolution of the CPU waster
 					tolerance := max(multiplyDurationByPercentage(expectedCPUUsage, 10), time.Second)