src/runtime/mcleanup_test.go

// Copyright 2024 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime_test

import (
	"internal/abi"
	"internal/runtime/atomic"
	"runtime"
	"sync"
	"testing"
	"time"
	"unsafe"
	"weak"
)

func TestCleanup(t *testing.T) {
	ch := make(chan bool, 1)
	done := make(chan bool, 1)
	want := 97531
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			if x != want {
				t.Errorf("cleanup %d, want %d", x, want)
			}
			ch <- true
		}
		runtime.AddCleanup(v, cleanup, 97531)
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
	<-ch
}

func TestCleanupMultiple(t *testing.T) {
	ch := make(chan bool, 3)
	done := make(chan bool, 1)
	want := 97531
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			if x != want {
				t.Errorf("cleanup %d, want %d", x, want)
			}
			ch <- true
		}
		runtime.AddCleanup(v, cleanup, 97531)
		runtime.AddCleanup(v, cleanup, 97531)
		runtime.AddCleanup(v, cleanup, 97531)
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
	<-ch
	<-ch
	<-ch
}

func TestCleanupZeroSizedStruct(t *testing.T) {
	type Z struct{}
	z := new(Z)
	runtime.AddCleanup(z, func(s string) {}, "foo")
}

func TestCleanupNilInterface(t *testing.T) {
	ptr := new(*byte)
	// Test both empty and non-empty interfaces.
	runtime.AddCleanup(ptr, func(any) {}, nil).Stop()
	runtime.AddCleanup(ptr, func(error) {}, nil).Stop()
	runtime.KeepAlive(ptr)
}

func TestCleanupInterfaceArgument(t *testing.T) {
	ptr := new(*byte) // Avoid the tiny allocator.
	var data [128]byte
	for i := range data {
		data[i] = byte(i + 1)
	}
	var arg any = data
	// Converting data to any boxes a copy of the array. AddCleanup copies
	// the interface value, so it retains the boxed array but not the local
	// variables data or arg. Observe the backing allocation, not &data or &arg.
	iface := (*abi.EmptyInterface)(unsafe.Pointer(&arg))
	w := weak.Make((*byte)(iface.Data))
	cleanup := runtime.AddCleanup(ptr, func(any) {}, arg)
	arg = nil // Only the cleanup should retain the boxed array.

	// On 32-bit systems, using the dynamic argument type allocated the
	// cleanup's interface storage without a pointer mask for its data pointer.
	runtime.GC()
	if w.Value() == nil {
		t.Error("cleanup argument was collected while the target was still live")
	}
	cleanup.Stop()
	runtime.KeepAlive(ptr)
}

func TestCleanupAfterFinalizer(t *testing.T) {
	ch := make(chan int, 2)
	done := make(chan bool, 1)
	want := 97531
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		finalizer := func(x *int) {
			ch <- 1
		}
		cleanup := func(x int) {
			if x != want {
				t.Errorf("cleanup %d, want %d", x, want)
			}
			ch <- 2
		}
		runtime.AddCleanup(v, cleanup, 97531)
		runtime.SetFinalizer(v, finalizer)
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
	var result int
	result = <-ch
	if result != 1 {
		t.Errorf("result %d, want 1", result)
	}
	runtime.GC()
	result = <-ch
	if result != 2 {
		t.Errorf("result %d, want 2", result)
	}
}

func TestCleanupInteriorPointer(t *testing.T) {
	ch := make(chan bool, 3)
	done := make(chan bool, 1)
	want := 97531
	go func() {
		// Allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			p unsafe.Pointer
			i int
			a int
			b int
			c int
		}
		ts := new(T)
		ts.a = 97531
		ts.b = 97531
		ts.c = 97531
		cleanup := func(x int) {
			if x != want {
				t.Errorf("cleanup %d, want %d", x, want)
			}
			ch <- true
		}
		runtime.AddCleanup(&ts.a, cleanup, 97531)
		runtime.AddCleanup(&ts.b, cleanup, 97531)
		runtime.AddCleanup(&ts.c, cleanup, 97531)
		ts = nil
		done <- true
	}()
	<-done
	runtime.GC()
	<-ch
	<-ch
	<-ch
}

func TestCleanupStop(t *testing.T) {
	done := make(chan bool, 1)
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			t.Error("cleanup called, want no cleanup called")
		}
		c := runtime.AddCleanup(v, cleanup, 97531)
		c.Stop()
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
}

func TestCleanupStopMultiple(t *testing.T) {
	done := make(chan bool, 1)
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			t.Error("cleanup called, want no cleanup called")
		}
		c := runtime.AddCleanup(v, cleanup, 97531)
		c.Stop()
		c.Stop()
		c.Stop()
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
}

func TestCleanupStopinterleavedMultiple(t *testing.T) {
	ch := make(chan bool, 3)
	done := make(chan bool, 1)
	go func() {
		// allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			if x != 1 {
				t.Error("cleanup called, want no cleanup called")
			}
			ch <- true
		}
		runtime.AddCleanup(v, cleanup, 1)
		runtime.AddCleanup(v, cleanup, 2).Stop()
		runtime.AddCleanup(v, cleanup, 1)
		runtime.AddCleanup(v, cleanup, 2).Stop()
		runtime.AddCleanup(v, cleanup, 1)
		v = nil
		done <- true
	}()
	<-done
	runtime.GC()
	<-ch
	<-ch
	<-ch
}

func TestCleanupStopAfterCleanupRuns(t *testing.T) {
	ch := make(chan bool, 1)
	done := make(chan bool, 1)
	var stop func()
	go func() {
		// Allocate struct with pointer to avoid hitting tinyalloc.
		// Otherwise we can't be sure when the allocation will
		// be freed.
		type T struct {
			v int
			p unsafe.Pointer
		}
		v := &new(T).v
		*v = 97531
		cleanup := func(x int) {
			ch <- true
		}
		cl := runtime.AddCleanup(v, cleanup, 97531)
		v = nil
		stop = cl.Stop
		done <- true
	}()
	<-done
	runtime.GC()
	<-ch
	stop()
}

func TestCleanupPointerEqualsArg(t *testing.T) {
	// See go.dev/issue/71316
	defer func() {
		want := "runtime.AddCleanup: ptr is equal to arg, cleanup will never run"
		if r := recover(); r == nil {
			t.Error("want panic, test did not panic")
		} else if r == want {
			// do nothing
		} else {
			t.Errorf("wrong panic: want=%q, got=%q", want, r)
		}
	}()

	// allocate struct with pointer to avoid hitting tinyalloc.
	// Otherwise we can't be sure when the allocation will
	// be freed.
	type T struct {
		v int
		p unsafe.Pointer
	}
	v := &new(T).v
	*v = 97531
	runtime.AddCleanup(v, func(x *int) {}, v)
	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()
	timeout := 10 * time.Second
	empty := runtime.BlockUntilEmptyCleanupQueue(int64(timeout))
	if !empty {
		t.Errorf("failed to drain cleanup queue within %s", timeout)
	}

	if got := int(got.Load()); got != want {
		t.Errorf("%d cleanups executed, expected %d", got, want)
	}
}

func TestCleanupUnreachablePointer(t *testing.T) {
	defer func() {
		if recover() == nil {
			t.Error("AddCleanup failed to detect self-pointer")
		}
	}()

	type T struct {
		p *byte // use *byte to avoid tiny allocator
		f int
	}
	v := &T{}
	runtime.AddCleanup(v, func(*int) {
		t.Error("cleanup ran unexpectedly")
	}, &v.f)
}

func TestCleanupUnreachableClosure(t *testing.T) {
	defer func() {
		if recover() == nil {
			t.Error("AddCleanup failed to detect closure pointer")
		}
	}()

	type T struct {
		p *byte // use *byte to avoid tiny allocator
		f int
	}
	v := &T{}
	runtime.AddCleanup(v, func(int) {
		t.Log(v.f)
		t.Error("cleanup ran unexpectedly")
	}, 0)
}

// BenchmarkAddCleanupAndStop benchmarks adding and removing a cleanup
// from the same allocation.
//
// At face value, this benchmark is unrealistic, since no program would
// do this in practice. However, adding cleanups to new allocations in a
// loop is also unrealistic. It adds additional unused allocations,
// exercises uncommon performance pitfalls in AddCleanup (traversing the
// specials list, which should just be its own benchmark), and executing
// cleanups at a frequency that is unlikely to appear in real programs.
//
// This benchmark is still useful however, since we can get a low-noise
// measurement of the cost of AddCleanup and Stop all in one without the
// above pitfalls: we can measure the pure overhead. We can then separate
// out the cost of each in CPU profiles if we so choose (they're not so
// inexpensive as to make this infeasible).
func BenchmarkAddCleanupAndStop(b *testing.B) {
	b.ReportAllocs()

	type T struct {
		v int
		p unsafe.Pointer
	}
	x := new(T)
	for b.Loop() {
		runtime.AddCleanup(x, func(int) {}, 14).Stop()
	}
}