1 files changed, 40 insertions, 0 deletions
diff --git a/src/runtime/mcleanup_test.go b/src/runtime/mcleanup_test.go
index d62356feef..22b9eccd20 100644
--- a/src/runtime/mcleanup_test.go
+++ b/src/runtime/mcleanup_test.go
@@ -5,8 +5,11 @@
 package runtime_test
 
 import (
+	"internal/runtime/atomic"
 	"runtime"
+	"sync"
 	"testing"
+	"time"
 	"unsafe"
 )
 
@@ -296,3 +299,40 @@ func TestCleanupPointerEqualsArg(t *testing.T) {
 	v = nil
 	runtime.GC()
 }
+
+// Checks to make sure cleanups aren't lost when there are a lot of them.
+func TestCleanupLost(t *testing.T) {
+	type T struct {
+		v int
+		p unsafe.Pointer
+	}
+
+	cleanups := 10_000
+	if testing.Short() {
+		cleanups = 100
+	}
+	n := runtime.GOMAXPROCS(-1)
+	want := n * cleanups
+	var got atomic.Uint64
+	var wg sync.WaitGroup
+	for i := range n {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+
+			for range cleanups {
+				v := &new(T).v
+				*v = 97531
+				runtime.AddCleanup(v, func(_ int) {
+					got.Add(1)
+				}, 97531)
+			}
+		}(i)
+	}
+	wg.Wait()
+	runtime.GC()
+	runtime.BlockUntilEmptyCleanupQueue(int64(10 * time.Second))
+	if got := int(got.Load()); got != want {
+		t.Errorf("expected %d cleanups to be executed, got %d", got, want)
+	}
+}