Adding upstream version 1.21.8.upstream/1.21.8

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 1674 insertions, 0 deletions

diff --git a/src/runtime/trace/annotation.go b/src/runtime/trace/annotation.go
new file mode 100644
index 0000000..2666d14
--- /dev/null
+++ b/src/runtime/trace/annotation.go
@@ -0,0 +1,198 @@
+// Copyright 2018 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 trace
+
+import (
+	"context"
+	"fmt"
+	"sync/atomic"
+	_ "unsafe"
+)
+
+type traceContextKey struct{}
+
+// NewTask creates a task instance with the type taskType and returns
+// it along with a Context that carries the task.
+// If the input context contains a task, the new task is its subtask.
+//
+// The taskType is used to classify task instances. Analysis tools
+// like the Go execution tracer may assume there are only a bounded
+// number of unique task types in the system.
+//
+// The returned Task's [Task.End] method is used to mark the task's end.
+// The trace tool measures task latency as the time between task creation
+// and when the End method is called, and provides the latency
+// distribution per task type.
+// If the End method is called multiple times, only the first
+// call is used in the latency measurement.
+//
+//	ctx, task := trace.NewTask(ctx, "awesomeTask")
+//	trace.WithRegion(ctx, "preparation", prepWork)
+//	// preparation of the task
+//	go func() {  // continue processing the task in a separate goroutine.
+//	    defer task.End()
+//	    trace.WithRegion(ctx, "remainingWork", remainingWork)
+//	}()
+func NewTask(pctx context.Context, taskType string) (ctx context.Context, task *Task) {
+	pid := fromContext(pctx).id
+	id := newID()
+	userTaskCreate(id, pid, taskType)
+	s := &Task{id: id}
+	return context.WithValue(pctx, traceContextKey{}, s), s
+
+	// We allocate a new task even when
+	// the tracing is disabled because the context and task
+	// can be used across trace enable/disable boundaries,
+	// which complicates the problem.
+	//
+	// For example, consider the following scenario:
+	//   - trace is enabled.
+	//   - trace.WithRegion is called, so a new context ctx
+	//     with a new region is created.
+	//   - trace is disabled.
+	//   - trace is enabled again.
+	//   - trace APIs with the ctx is called. Is the ID in the task
+	//   a valid one to use?
+	//
+	// TODO(hyangah): reduce the overhead at least when
+	// tracing is disabled. Maybe the id can embed a tracing
+	// round number and ignore ids generated from previous
+	// tracing round.
+}
+
+func fromContext(ctx context.Context) *Task {
+	if s, ok := ctx.Value(traceContextKey{}).(*Task); ok {
+		return s
+	}
+	return &bgTask
+}
+
+// Task is a data type for tracing a user-defined, logical operation.
+type Task struct {
+	id uint64
+	// TODO(hyangah): record parent id?
+}
+
+// End marks the end of the operation represented by the [Task].
+func (t *Task) End() {
+	userTaskEnd(t.id)
+}
+
+var lastTaskID uint64 = 0 // task id issued last time
+
+func newID() uint64 {
+	// TODO(hyangah): use per-P cache
+	return atomic.AddUint64(&lastTaskID, 1)
+}
+
+var bgTask = Task{id: uint64(0)}
+
+// Log emits a one-off event with the given category and message.
+// Category can be empty and the API assumes there are only a handful of
+// unique categories in the system.
+func Log(ctx context.Context, category, message string) {
+	id := fromContext(ctx).id
+	userLog(id, category, message)
+}
+
+// Logf is like [Log], but the value is formatted using the specified format spec.
+func Logf(ctx context.Context, category, format string, args ...any) {
+	if IsEnabled() {
+		// Ideally this should be just Log, but that will
+		// add one more frame in the stack trace.
+		id := fromContext(ctx).id
+		userLog(id, category, fmt.Sprintf(format, args...))
+	}
+}
+
+const (
+	regionStartCode = uint64(0)
+	regionEndCode   = uint64(1)
+)
+
+// WithRegion starts a region associated with its calling goroutine, runs fn,
+// and then ends the region. If the context carries a task, the region is
+// associated with the task. Otherwise, the region is attached to the background
+// task.
+//
+// The regionType is used to classify regions, so there should be only a
+// handful of unique region types.
+func WithRegion(ctx context.Context, regionType string, fn func()) {
+	// NOTE:
+	// WithRegion helps avoiding misuse of the API but in practice,
+	// this is very restrictive:
+	// - Use of WithRegion makes the stack traces captured from
+	//   region start and end are identical.
+	// - Refactoring the existing code to use WithRegion is sometimes
+	//   hard and makes the code less readable.
+	//     e.g. code block nested deep in the loop with various
+	//          exit point with return values
+	// - Refactoring the code to use this API with closure can
+	//   cause different GC behavior such as retaining some parameters
+	//   longer.
+	// This causes more churns in code than I hoped, and sometimes
+	// makes the code less readable.
+
+	id := fromContext(ctx).id
+	userRegion(id, regionStartCode, regionType)
+	defer userRegion(id, regionEndCode, regionType)
+	fn()
+}
+
+// StartRegion starts a region and returns it.
+// The returned Region's [Region.End] method must be called
+// from the same goroutine where the region was started.
+// Within each goroutine, regions must nest. That is, regions started
+// after this region must be ended before this region can be ended.
+// Recommended usage is
+//
+//	defer trace.StartRegion(ctx, "myTracedRegion").End()
+func StartRegion(ctx context.Context, regionType string) *Region {
+	if !IsEnabled() {
+		return noopRegion
+	}
+	id := fromContext(ctx).id
+	userRegion(id, regionStartCode, regionType)
+	return &Region{id, regionType}
+}
+
+// Region is a region of code whose execution time interval is traced.
+type Region struct {
+	id         uint64
+	regionType string
+}
+
+var noopRegion = &Region{}
+
+// End marks the end of the traced code region.
+func (r *Region) End() {
+	if r == noopRegion {
+		return
+	}
+	userRegion(r.id, regionEndCode, r.regionType)
+}
+
+// IsEnabled reports whether tracing is enabled.
+// The information is advisory only. The tracing status
+// may have changed by the time this function returns.
+func IsEnabled() bool {
+	return tracing.enabled.Load()
+}
+
+//
+// Function bodies are defined in runtime/trace.go
+//
+
+// emits UserTaskCreate event.
+func userTaskCreate(id, parentID uint64, taskType string)
+
+// emits UserTaskEnd event.
+func userTaskEnd(id uint64)
+
+// emits UserRegion event.
+func userRegion(id, mode uint64, regionType string)
+
+// emits UserLog event.
+func userLog(id uint64, category, message string)
diff --git a/src/runtime/trace/annotation_test.go b/src/runtime/trace/annotation_test.go
new file mode 100644
index 0000000..69ea8f2
--- /dev/null
+++ b/src/runtime/trace/annotation_test.go
@@ -0,0 +1,156 @@
+// Copyright 2018 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 trace_test
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	"internal/trace"
+	"reflect"
+	. "runtime/trace"
+	"strings"
+	"sync"
+	"testing"
+)
+
+func BenchmarkStartRegion(b *testing.B) {
+	b.ReportAllocs()
+	ctx, task := NewTask(context.Background(), "benchmark")
+	defer task.End()
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			StartRegion(ctx, "region").End()
+		}
+	})
+}
+
+func BenchmarkNewTask(b *testing.B) {
+	b.ReportAllocs()
+	pctx, task := NewTask(context.Background(), "benchmark")
+	defer task.End()
+
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			_, task := NewTask(pctx, "task")
+			task.End()
+		}
+	})
+}
+
+func TestUserTaskRegion(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	bgctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	preExistingRegion := StartRegion(bgctx, "pre-existing region")
+
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+
+	// Beginning of traced execution
+	var wg sync.WaitGroup
+	ctx, task := NewTask(bgctx, "task0") // EvUserTaskCreate("task0")
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		defer task.End() // EvUserTaskEnd("task0")
+
+		WithRegion(ctx, "region0", func() {
+			// EvUserRegionCreate("region0", start)
+			WithRegion(ctx, "region1", func() {
+				Log(ctx, "key0", "0123456789abcdef") // EvUserLog("task0", "key0", "0....f")
+			})
+			// EvUserRegion("region0", end)
+		})
+	}()
+
+	wg.Wait()
+
+	preExistingRegion.End()
+	postExistingRegion := StartRegion(bgctx, "post-existing region")
+
+	// End of traced execution
+	Stop()
+
+	postExistingRegion.End()
+
+	saveTrace(t, buf, "TestUserTaskRegion")
+	res, err := trace.Parse(buf, "")
+	if err == trace.ErrTimeOrder {
+		// golang.org/issues/16755
+		t.Skipf("skipping trace: %v", err)
+	}
+	if err != nil {
+		t.Fatalf("Parse failed: %v", err)
+	}
+
+	// Check whether we see all user annotation related records in order
+	type testData struct {
+		typ     byte
+		strs    []string
+		args    []uint64
+		setLink bool
+	}
+
+	var got []testData
+	tasks := map[uint64]string{}
+	for _, e := range res.Events {
+		t.Logf("%s", e)
+		switch e.Type {
+		case trace.EvUserTaskCreate:
+			taskName := e.SArgs[0]
+			got = append(got, testData{trace.EvUserTaskCreate, []string{taskName}, nil, e.Link != nil})
+			if e.Link != nil && e.Link.Type != trace.EvUserTaskEnd {
+				t.Errorf("Unexpected linked event %q->%q", e, e.Link)
+			}
+			tasks[e.Args[0]] = taskName
+		case trace.EvUserLog:
+			key, val := e.SArgs[0], e.SArgs[1]
+			taskName := tasks[e.Args[0]]
+			got = append(got, testData{trace.EvUserLog, []string{taskName, key, val}, nil, e.Link != nil})
+		case trace.EvUserTaskEnd:
+			taskName := tasks[e.Args[0]]
+			got = append(got, testData{trace.EvUserTaskEnd, []string{taskName}, nil, e.Link != nil})
+			if e.Link != nil && e.Link.Type != trace.EvUserTaskCreate {
+				t.Errorf("Unexpected linked event %q->%q", e, e.Link)
+			}
+		case trace.EvUserRegion:
+			taskName := tasks[e.Args[0]]
+			regionName := e.SArgs[0]
+			got = append(got, testData{trace.EvUserRegion, []string{taskName, regionName}, []uint64{e.Args[1]}, e.Link != nil})
+			if e.Link != nil && (e.Link.Type != trace.EvUserRegion || e.Link.SArgs[0] != regionName) {
+				t.Errorf("Unexpected linked event %q->%q", e, e.Link)
+			}
+		}
+	}
+	want := []testData{
+		{trace.EvUserTaskCreate, []string{"task0"}, nil, true},
+		{trace.EvUserRegion, []string{"task0", "region0"}, []uint64{0}, true},
+		{trace.EvUserRegion, []string{"task0", "region1"}, []uint64{0}, true},
+		{trace.EvUserLog, []string{"task0", "key0", "0123456789abcdef"}, nil, false},
+		{trace.EvUserRegion, []string{"task0", "region1"}, []uint64{1}, false},
+		{trace.EvUserRegion, []string{"task0", "region0"}, []uint64{1}, false},
+		{trace.EvUserTaskEnd, []string{"task0"}, nil, false},
+		//  Currently, pre-existing region is not recorded to avoid allocations.
+		//  {trace.EvUserRegion, []string{"", "pre-existing region"}, []uint64{1}, false},
+		{trace.EvUserRegion, []string{"", "post-existing region"}, []uint64{0}, false},
+	}
+	if !reflect.DeepEqual(got, want) {
+		pretty := func(data []testData) string {
+			var s strings.Builder
+			for _, d := range data {
+				fmt.Fprintf(&s, "\t%+v\n", d)
+			}
+			return s.String()
+		}
+		t.Errorf("Got user region related events\n%+v\nwant:\n%+v", pretty(got), pretty(want))
+	}
+}
diff --git a/src/runtime/trace/example_test.go b/src/runtime/trace/example_test.go
new file mode 100644
index 0000000..ba96a82
--- /dev/null
+++ b/src/runtime/trace/example_test.go
@@ -0,0 +1,39 @@
+// Copyright 2017 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 trace_test
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"runtime/trace"
+)
+
+// Example demonstrates the use of the trace package to trace
+// the execution of a Go program. The trace output will be
+// written to the file trace.out
+func Example() {
+	f, err := os.Create("trace.out")
+	if err != nil {
+		log.Fatalf("failed to create trace output file: %v", err)
+	}
+	defer func() {
+		if err := f.Close(); err != nil {
+			log.Fatalf("failed to close trace file: %v", err)
+		}
+	}()
+
+	if err := trace.Start(f); err != nil {
+		log.Fatalf("failed to start trace: %v", err)
+	}
+	defer trace.Stop()
+
+	// your program here
+	RunMyProgram()
+}
+
+func RunMyProgram() {
+	fmt.Printf("this function will be traced")
+}
diff --git a/src/runtime/trace/trace.go b/src/runtime/trace/trace.go
new file mode 100644
index 0000000..935d222
--- /dev/null
+++ b/src/runtime/trace/trace.go
@@ -0,0 +1,154 @@
+// Copyright 2015 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 trace contains facilities for programs to generate traces
+// for the Go execution tracer.
+//
+// # Tracing runtime activities
+//
+// The execution trace captures a wide range of execution events such as
+// goroutine creation/blocking/unblocking, syscall enter/exit/block,
+// GC-related events, changes of heap size, processor start/stop, etc.
+// When CPU profiling is active, the execution tracer makes an effort to
+// include those samples as well.
+// A precise nanosecond-precision timestamp and a stack trace is
+// captured for most events. The generated trace can be interpreted
+// using `go tool trace`.
+//
+// Support for tracing tests and benchmarks built with the standard
+// testing package is built into `go test`. For example, the following
+// command runs the test in the current directory and writes the trace
+// file (trace.out).
+//
+//	go test -trace=trace.out
+//
+// This runtime/trace package provides APIs to add equivalent tracing
+// support to a standalone program. See the Example that demonstrates
+// how to use this API to enable tracing.
+//
+// There is also a standard HTTP interface to trace data. Adding the
+// following line will install a handler under the /debug/pprof/trace URL
+// to download a live trace:
+//
+//	import _ "net/http/pprof"
+//
+// See the [net/http/pprof] package for more details about all of the
+// debug endpoints installed by this import.
+//
+// # User annotation
+//
+// Package trace provides user annotation APIs that can be used to
+// log interesting events during execution.
+//
+// There are three types of user annotations: log messages, regions,
+// and tasks.
+//
+// [Log] emits a timestamped message to the execution trace along with
+// additional information such as the category of the message and
+// which goroutine called [Log]. The execution tracer provides UIs to filter
+// and group goroutines using the log category and the message supplied
+// in [Log].
+//
+// A region is for logging a time interval during a goroutine's execution.
+// By definition, a region starts and ends in the same goroutine.
+// Regions can be nested to represent subintervals.
+// For example, the following code records four regions in the execution
+// trace to trace the durations of sequential steps in a cappuccino making
+// operation.
+//
+//	trace.WithRegion(ctx, "makeCappuccino", func() {
+//
+//	   // orderID allows to identify a specific order
+//	   // among many cappuccino order region records.
+//	   trace.Log(ctx, "orderID", orderID)
+//
+//	   trace.WithRegion(ctx, "steamMilk", steamMilk)
+//	   trace.WithRegion(ctx, "extractCoffee", extractCoffee)
+//	   trace.WithRegion(ctx, "mixMilkCoffee", mixMilkCoffee)
+//	})
+//
+// A task is a higher-level component that aids tracing of logical
+// operations such as an RPC request, an HTTP request, or an
+// interesting local operation which may require multiple goroutines
+// working together. Since tasks can involve multiple goroutines,
+// they are tracked via a [context.Context] object. [NewTask] creates
+// a new task and embeds it in the returned [context.Context] object.
+// Log messages and regions are attached to the task, if any, in the
+// Context passed to [Log] and [WithRegion].
+//
+// For example, assume that we decided to froth milk, extract coffee,
+// and mix milk and coffee in separate goroutines. With a task,
+// the trace tool can identify the goroutines involved in a specific
+// cappuccino order.
+//
+//	ctx, task := trace.NewTask(ctx, "makeCappuccino")
+//	trace.Log(ctx, "orderID", orderID)
+//
+//	milk := make(chan bool)
+//	espresso := make(chan bool)
+//
+//	go func() {
+//	        trace.WithRegion(ctx, "steamMilk", steamMilk)
+//	        milk <- true
+//	}()
+//	go func() {
+//	        trace.WithRegion(ctx, "extractCoffee", extractCoffee)
+//	        espresso <- true
+//	}()
+//	go func() {
+//	        defer task.End() // When assemble is done, the order is complete.
+//	        <-espresso
+//	        <-milk
+//	        trace.WithRegion(ctx, "mixMilkCoffee", mixMilkCoffee)
+//	}()
+//
+// The trace tool computes the latency of a task by measuring the
+// time between the task creation and the task end and provides
+// latency distributions for each task type found in the trace.
+package trace
+
+import (
+	"io"
+	"runtime"
+	"sync"
+	"sync/atomic"
+)
+
+// Start enables tracing for the current program.
+// While tracing, the trace will be buffered and written to w.
+// Start returns an error if tracing is already enabled.
+func Start(w io.Writer) error {
+	tracing.Lock()
+	defer tracing.Unlock()
+
+	if err := runtime.StartTrace(); err != nil {
+		return err
+	}
+	go func() {
+		for {
+			data := runtime.ReadTrace()
+			if data == nil {
+				break
+			}
+			w.Write(data)
+		}
+	}()
+	tracing.enabled.Store(true)
+	return nil
+}
+
+// Stop stops the current tracing, if any.
+// Stop only returns after all the writes for the trace have completed.
+func Stop() {
+	tracing.Lock()
+	defer tracing.Unlock()
+	tracing.enabled.Store(false)
+
+	runtime.StopTrace()
+}
+
+var tracing struct {
+	sync.Mutex // gate mutators (Start, Stop)
+	enabled    atomic.Bool
+}
diff --git a/src/runtime/trace/trace_stack_test.go b/src/runtime/trace/trace_stack_test.go
new file mode 100644
index 0000000..be3adc9
--- /dev/null
+++ b/src/runtime/trace/trace_stack_test.go
@@ -0,0 +1,333 @@
+// Copyright 2014 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 trace_test
+
+import (
+	"bytes"
+	"fmt"
+	"internal/testenv"
+	"internal/trace"
+	"net"
+	"os"
+	"runtime"
+	. "runtime/trace"
+	"strings"
+	"sync"
+	"testing"
+	"text/tabwriter"
+	"time"
+)
+
+// TestTraceSymbolize tests symbolization and that events has proper stacks.
+// In particular that we strip bottom uninteresting frames like goexit,
+// top uninteresting frames (runtime guts).
+func TestTraceSymbolize(t *testing.T) {
+	skipTraceSymbolizeTestIfNecessary(t)
+
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	defer Stop() // in case of early return
+
+	// Now we will do a bunch of things for which we verify stacks later.
+	// It is impossible to ensure that a goroutine has actually blocked
+	// on a channel, in a select or otherwise. So we kick off goroutines
+	// that need to block first in the hope that while we are executing
+	// the rest of the test, they will block.
+	go func() { // func1
+		select {}
+	}()
+	go func() { // func2
+		var c chan int
+		c <- 0
+	}()
+	go func() { // func3
+		var c chan int
+		<-c
+	}()
+	done1 := make(chan bool)
+	go func() { // func4
+		<-done1
+	}()
+	done2 := make(chan bool)
+	go func() { // func5
+		done2 <- true
+	}()
+	c1 := make(chan int)
+	c2 := make(chan int)
+	go func() { // func6
+		select {
+		case <-c1:
+		case <-c2:
+		}
+	}()
+	var mu sync.Mutex
+	mu.Lock()
+	go func() { // func7
+		mu.Lock()
+		mu.Unlock()
+	}()
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() { // func8
+		wg.Wait()
+	}()
+	cv := sync.NewCond(&sync.Mutex{})
+	go func() { // func9
+		cv.L.Lock()
+		cv.Wait()
+		cv.L.Unlock()
+	}()
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("failed to listen: %v", err)
+	}
+	go func() { // func10
+		c, err := ln.Accept()
+		if err != nil {
+			t.Errorf("failed to accept: %v", err)
+			return
+		}
+		c.Close()
+	}()
+	rp, wp, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create a pipe: %v", err)
+	}
+	defer rp.Close()
+	defer wp.Close()
+	pipeReadDone := make(chan bool)
+	go func() { // func11
+		var data [1]byte
+		rp.Read(data[:])
+		pipeReadDone <- true
+	}()
+
+	time.Sleep(100 * time.Millisecond)
+	runtime.GC()
+	runtime.Gosched()
+	time.Sleep(100 * time.Millisecond) // the last chance for the goroutines above to block
+	done1 <- true
+	<-done2
+	select {
+	case c1 <- 0:
+	case c2 <- 0:
+	}
+	mu.Unlock()
+	wg.Done()
+	cv.Signal()
+	c, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("failed to dial: %v", err)
+	}
+	c.Close()
+	var data [1]byte
+	wp.Write(data[:])
+	<-pipeReadDone
+
+	oldGoMaxProcs := runtime.GOMAXPROCS(0)
+	runtime.GOMAXPROCS(oldGoMaxProcs + 1)
+
+	Stop()
+
+	runtime.GOMAXPROCS(oldGoMaxProcs)
+
+	events, _ := parseTrace(t, buf)
+
+	// Now check that the stacks are correct.
+	type eventDesc struct {
+		Type byte
+		Stk  []frame
+	}
+	want := []eventDesc{
+		{trace.EvGCStart, []frame{
+			{"runtime.GC", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 0},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoStart, []frame{
+			{"runtime/trace_test.TestTraceSymbolize.func1", 0},
+		}},
+		{trace.EvGoSched, []frame{
+			{"runtime/trace_test.TestTraceSymbolize", 111},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoCreate, []frame{
+			{"runtime/trace_test.TestTraceSymbolize", 40},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoStop, []frame{
+			{"runtime.block", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func1", 0},
+		}},
+		{trace.EvGoStop, []frame{
+			{"runtime.chansend1", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func2", 0},
+		}},
+		{trace.EvGoStop, []frame{
+			{"runtime.chanrecv1", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func3", 0},
+		}},
+		{trace.EvGoBlockRecv, []frame{
+			{"runtime.chanrecv1", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func4", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"runtime.chansend1", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 113},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoBlockSend, []frame{
+			{"runtime.chansend1", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func5", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"runtime.chanrecv1", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 114},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoBlockSelect, []frame{
+			{"runtime.selectgo", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func6", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"runtime.selectgo", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 115},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoBlockSync, []frame{
+			{"sync.(*Mutex).Lock", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func7", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"sync.(*Mutex).Unlock", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 0},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoBlockSync, []frame{
+			{"sync.(*WaitGroup).Wait", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func8", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"sync.(*WaitGroup).Add", 0},
+			{"sync.(*WaitGroup).Done", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 120},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoBlockCond, []frame{
+			{"sync.(*Cond).Wait", 0},
+			{"runtime/trace_test.TestTraceSymbolize.func9", 0},
+		}},
+		{trace.EvGoUnblock, []frame{
+			{"sync.(*Cond).Signal", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 0},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGoSleep, []frame{
+			{"time.Sleep", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 0},
+			{"testing.tRunner", 0},
+		}},
+		{trace.EvGomaxprocs, []frame{
+			{"runtime.startTheWorld", 0}, // this is when the current gomaxprocs is logged.
+			{"runtime.startTheWorldGC", 0},
+			{"runtime.GOMAXPROCS", 0},
+			{"runtime/trace_test.TestTraceSymbolize", 0},
+			{"testing.tRunner", 0},
+		}},
+	}
+	// Stacks for the following events are OS-dependent due to OS-specific code in net package.
+	if runtime.GOOS != "windows" && runtime.GOOS != "plan9" {
+		want = append(want, []eventDesc{
+			{trace.EvGoBlockNet, []frame{
+				{"internal/poll.(*FD).Accept", 0},
+				{"net.(*netFD).accept", 0},
+				{"net.(*TCPListener).accept", 0},
+				{"net.(*TCPListener).Accept", 0},
+				{"runtime/trace_test.TestTraceSymbolize.func10", 0},
+			}},
+			{trace.EvGoSysCall, []frame{
+				{"syscall.read", 0},
+				{"syscall.Read", 0},
+				{"internal/poll.ignoringEINTRIO", 0},
+				{"internal/poll.(*FD).Read", 0},
+				{"os.(*File).read", 0},
+				{"os.(*File).Read", 0},
+				{"runtime/trace_test.TestTraceSymbolize.func11", 0},
+			}},
+		}...)
+	}
+	matched := make([]bool, len(want))
+	for _, ev := range events {
+	wantLoop:
+		for i, w := range want {
+			if matched[i] || w.Type != ev.Type || len(w.Stk) != len(ev.Stk) {
+				continue
+			}
+
+			for fi, f := range ev.Stk {
+				wf := w.Stk[fi]
+				if wf.Fn != f.Fn || wf.Line != 0 && wf.Line != f.Line {
+					continue wantLoop
+				}
+			}
+			matched[i] = true
+		}
+	}
+	for i, w := range want {
+		if matched[i] {
+			continue
+		}
+		seen, n := dumpEventStacks(w.Type, events)
+		t.Errorf("Did not match event %v with stack\n%s\nSeen %d events of the type\n%s",
+			trace.EventDescriptions[w.Type].Name, dumpFrames(w.Stk), n, seen)
+	}
+}
+
+func skipTraceSymbolizeTestIfNecessary(t *testing.T) {
+	testenv.MustHaveGoBuild(t)
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+}
+
+func dumpEventStacks(typ byte, events []*trace.Event) ([]byte, int) {
+	matched := 0
+	o := new(bytes.Buffer)
+	tw := tabwriter.NewWriter(o, 0, 8, 0, '\t', 0)
+	for _, ev := range events {
+		if ev.Type != typ {
+			continue
+		}
+		matched++
+		fmt.Fprintf(tw, "Offset %d\n", ev.Off)
+		for _, f := range ev.Stk {
+			fname := f.File
+			if idx := strings.Index(fname, "/go/src/"); idx > 0 {
+				fname = fname[idx:]
+			}
+			fmt.Fprintf(tw, "  %v\t%s:%d\n", f.Fn, fname, f.Line)
+		}
+	}
+	tw.Flush()
+	return o.Bytes(), matched
+}
+
+type frame struct {
+	Fn   string
+	Line int
+}
+
+func dumpFrames(frames []frame) []byte {
+	o := new(bytes.Buffer)
+	tw := tabwriter.NewWriter(o, 0, 8, 0, '\t', 0)
+
+	for _, f := range frames {
+		fmt.Fprintf(tw, "  %v\t :%d\n", f.Fn, f.Line)
+	}
+	tw.Flush()
+	return o.Bytes()
+}
diff --git a/src/runtime/trace/trace_test.go b/src/runtime/trace/trace_test.go
new file mode 100644
index 0000000..04a43a0
--- /dev/null
+++ b/src/runtime/trace/trace_test.go
@@ -0,0 +1,794 @@
+// Copyright 2014 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 trace_test
+
+import (
+	"bytes"
+	"context"
+	"flag"
+	"fmt"
+	"internal/profile"
+	"internal/race"
+	"internal/trace"
+	"io"
+	"net"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	. "runtime/trace"
+	"strconv"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+var (
+	saveTraces = flag.Bool("savetraces", false, "save traces collected by tests")
+)
+
+// TestEventBatch tests Flush calls that happen during Start
+// don't produce corrupted traces.
+func TestEventBatch(t *testing.T) {
+	if race.Enabled {
+		t.Skip("skipping in race mode")
+	}
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	if testing.Short() {
+		t.Skip("skipping in short mode")
+	}
+	// During Start, bunch of records are written to reflect the current
+	// snapshot of the program, including state of each goroutines.
+	// And some string constants are written to the trace to aid trace
+	// parsing. This test checks Flush of the buffer occurred during
+	// this process doesn't cause corrupted traces.
+	// When a Flush is called during Start is complicated
+	// so we test with a range of number of goroutines hoping that one
+	// of them triggers Flush.
+	// This range was chosen to fill up a ~64KB buffer with traceEvGoCreate
+	// and traceEvGoWaiting events (12~13bytes per goroutine).
+	for g := 4950; g < 5050; g++ {
+		n := g
+		t.Run("G="+strconv.Itoa(n), func(t *testing.T) {
+			var wg sync.WaitGroup
+			wg.Add(n)
+
+			in := make(chan bool, 1000)
+			for i := 0; i < n; i++ {
+				go func() {
+					<-in
+					wg.Done()
+				}()
+			}
+			buf := new(bytes.Buffer)
+			if err := Start(buf); err != nil {
+				t.Fatalf("failed to start tracing: %v", err)
+			}
+
+			for i := 0; i < n; i++ {
+				in <- true
+			}
+			wg.Wait()
+			Stop()
+
+			_, err := trace.Parse(buf, "")
+			if err == trace.ErrTimeOrder {
+				t.Skipf("skipping trace: %v", err)
+			}
+
+			if err != nil {
+				t.Fatalf("failed to parse trace: %v", err)
+			}
+		})
+	}
+}
+
+func TestTraceStartStop(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	Stop()
+	size := buf.Len()
+	if size == 0 {
+		t.Fatalf("trace is empty")
+	}
+	time.Sleep(100 * time.Millisecond)
+	if size != buf.Len() {
+		t.Fatalf("trace writes after stop: %v -> %v", size, buf.Len())
+	}
+	saveTrace(t, buf, "TestTraceStartStop")
+}
+
+func TestTraceDoubleStart(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	Stop()
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	if err := Start(buf); err == nil {
+		t.Fatalf("succeed to start tracing second time")
+	}
+	Stop()
+	Stop()
+}
+
+func TestTrace(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+	Stop()
+	saveTrace(t, buf, "TestTrace")
+	_, err := trace.Parse(buf, "")
+	if err == trace.ErrTimeOrder {
+		t.Skipf("skipping trace: %v", err)
+	}
+	if err != nil {
+		t.Fatalf("failed to parse trace: %v", err)
+	}
+}
+
+func parseTrace(t *testing.T, r io.Reader) ([]*trace.Event, map[uint64]*trace.GDesc) {
+	res, err := trace.Parse(r, "")
+	if err == trace.ErrTimeOrder {
+		t.Skipf("skipping trace: %v", err)
+	}
+	if err != nil {
+		t.Fatalf("failed to parse trace: %v", err)
+	}
+	gs := trace.GoroutineStats(res.Events)
+	for goid := range gs {
+		// We don't do any particular checks on the result at the moment.
+		// But still check that RelatedGoroutines does not crash, hang, etc.
+		_ = trace.RelatedGoroutines(res.Events, goid)
+	}
+	return res.Events, gs
+}
+
+func testBrokenTimestamps(t *testing.T, data []byte) {
+	// On some processors cputicks (used to generate trace timestamps)
+	// produce non-monotonic timestamps. It is important that the parser
+	// distinguishes logically inconsistent traces (e.g. missing, excessive
+	// or misordered events) from broken timestamps. The former is a bug
+	// in tracer, the latter is a machine issue.
+	// So now that we have a consistent trace, test that (1) parser does
+	// not return a logical error in case of broken timestamps
+	// and (2) broken timestamps are eventually detected and reported.
+	trace.BreakTimestampsForTesting = true
+	defer func() {
+		trace.BreakTimestampsForTesting = false
+	}()
+	for i := 0; i < 1e4; i++ {
+		_, err := trace.Parse(bytes.NewReader(data), "")
+		if err == trace.ErrTimeOrder {
+			return
+		}
+		if err != nil {
+			t.Fatalf("failed to parse trace: %v", err)
+		}
+	}
+}
+
+func TestTraceStress(t *testing.T) {
+	switch runtime.GOOS {
+	case "js", "wasip1":
+		t.Skip("no os.Pipe on " + runtime.GOOS)
+	}
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	if testing.Short() {
+		t.Skip("skipping in -short mode")
+	}
+
+	var wg sync.WaitGroup
+	done := make(chan bool)
+
+	// Create a goroutine blocked before tracing.
+	wg.Add(1)
+	go func() {
+		<-done
+		wg.Done()
+	}()
+
+	// Create a goroutine blocked in syscall before tracing.
+	rp, wp, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create pipe: %v", err)
+	}
+	defer func() {
+		rp.Close()
+		wp.Close()
+	}()
+	wg.Add(1)
+	go func() {
+		var tmp [1]byte
+		rp.Read(tmp[:])
+		<-done
+		wg.Done()
+	}()
+	time.Sleep(time.Millisecond) // give the goroutine above time to block
+
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+
+	procs := runtime.GOMAXPROCS(10)
+	time.Sleep(50 * time.Millisecond) // test proc stop/start events
+
+	go func() {
+		runtime.LockOSThread()
+		for {
+			select {
+			case <-done:
+				return
+			default:
+				runtime.Gosched()
+			}
+		}
+	}()
+
+	runtime.GC()
+	// Trigger GC from malloc.
+	n := int(1e3)
+	if isMemoryConstrained() {
+		// Reduce allocation to avoid running out of
+		// memory on the builder - see issue/12032.
+		n = 512
+	}
+	for i := 0; i < n; i++ {
+		_ = make([]byte, 1<<20)
+	}
+
+	// Create a bunch of busy goroutines to load all Ps.
+	for p := 0; p < 10; p++ {
+		wg.Add(1)
+		go func() {
+			// Do something useful.
+			tmp := make([]byte, 1<<16)
+			for i := range tmp {
+				tmp[i]++
+			}
+			_ = tmp
+			<-done
+			wg.Done()
+		}()
+	}
+
+	// Block in syscall.
+	wg.Add(1)
+	go func() {
+		var tmp [1]byte
+		rp.Read(tmp[:])
+		<-done
+		wg.Done()
+	}()
+
+	// Test timers.
+	timerDone := make(chan bool)
+	go func() {
+		time.Sleep(time.Millisecond)
+		timerDone <- true
+	}()
+	<-timerDone
+
+	// A bit of network.
+	ln, err := net.Listen("tcp", "127.0.0.1:0")
+	if err != nil {
+		t.Fatalf("listen failed: %v", err)
+	}
+	defer ln.Close()
+	go func() {
+		c, err := ln.Accept()
+		if err != nil {
+			return
+		}
+		time.Sleep(time.Millisecond)
+		var buf [1]byte
+		c.Write(buf[:])
+		c.Close()
+	}()
+	c, err := net.Dial("tcp", ln.Addr().String())
+	if err != nil {
+		t.Fatalf("dial failed: %v", err)
+	}
+	var tmp [1]byte
+	c.Read(tmp[:])
+	c.Close()
+
+	go func() {
+		runtime.Gosched()
+		select {}
+	}()
+
+	// Unblock helper goroutines and wait them to finish.
+	wp.Write(tmp[:])
+	wp.Write(tmp[:])
+	close(done)
+	wg.Wait()
+
+	runtime.GOMAXPROCS(procs)
+
+	Stop()
+	saveTrace(t, buf, "TestTraceStress")
+	trace := buf.Bytes()
+	parseTrace(t, buf)
+	testBrokenTimestamps(t, trace)
+}
+
+// isMemoryConstrained reports whether the current machine is likely
+// to be memory constrained.
+// This was originally for the openbsd/arm builder (Issue 12032).
+// TODO: move this to testenv? Make this look at memory? Look at GO_BUILDER_NAME?
+func isMemoryConstrained() bool {
+	if runtime.GOOS == "plan9" {
+		return true
+	}
+	switch runtime.GOARCH {
+	case "arm", "mips", "mipsle":
+		return true
+	}
+	return false
+}
+
+// Do a bunch of various stuff (timers, GC, network, etc) in a separate goroutine.
+// And concurrently with all that start/stop trace 3 times.
+func TestTraceStressStartStop(t *testing.T) {
+	switch runtime.GOOS {
+	case "js", "wasip1":
+		t.Skip("no os.Pipe on " + runtime.GOOS)
+	}
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(8))
+	outerDone := make(chan bool)
+
+	go func() {
+		defer func() {
+			outerDone <- true
+		}()
+
+		var wg sync.WaitGroup
+		done := make(chan bool)
+
+		wg.Add(1)
+		go func() {
+			<-done
+			wg.Done()
+		}()
+
+		rp, wp, err := os.Pipe()
+		if err != nil {
+			t.Errorf("failed to create pipe: %v", err)
+			return
+		}
+		defer func() {
+			rp.Close()
+			wp.Close()
+		}()
+		wg.Add(1)
+		go func() {
+			var tmp [1]byte
+			rp.Read(tmp[:])
+			<-done
+			wg.Done()
+		}()
+		time.Sleep(time.Millisecond)
+
+		go func() {
+			runtime.LockOSThread()
+			for {
+				select {
+				case <-done:
+					return
+				default:
+					runtime.Gosched()
+				}
+			}
+		}()
+
+		runtime.GC()
+		// Trigger GC from malloc.
+		n := int(1e3)
+		if isMemoryConstrained() {
+			// Reduce allocation to avoid running out of
+			// memory on the builder.
+			n = 512
+		}
+		for i := 0; i < n; i++ {
+			_ = make([]byte, 1<<20)
+		}
+
+		// Create a bunch of busy goroutines to load all Ps.
+		for p := 0; p < 10; p++ {
+			wg.Add(1)
+			go func() {
+				// Do something useful.
+				tmp := make([]byte, 1<<16)
+				for i := range tmp {
+					tmp[i]++
+				}
+				_ = tmp
+				<-done
+				wg.Done()
+			}()
+		}
+
+		// Block in syscall.
+		wg.Add(1)
+		go func() {
+			var tmp [1]byte
+			rp.Read(tmp[:])
+			<-done
+			wg.Done()
+		}()
+
+		runtime.GOMAXPROCS(runtime.GOMAXPROCS(1))
+
+		// Test timers.
+		timerDone := make(chan bool)
+		go func() {
+			time.Sleep(time.Millisecond)
+			timerDone <- true
+		}()
+		<-timerDone
+
+		// A bit of network.
+		ln, err := net.Listen("tcp", "127.0.0.1:0")
+		if err != nil {
+			t.Errorf("listen failed: %v", err)
+			return
+		}
+		defer ln.Close()
+		go func() {
+			c, err := ln.Accept()
+			if err != nil {
+				return
+			}
+			time.Sleep(time.Millisecond)
+			var buf [1]byte
+			c.Write(buf[:])
+			c.Close()
+		}()
+		c, err := net.Dial("tcp", ln.Addr().String())
+		if err != nil {
+			t.Errorf("dial failed: %v", err)
+			return
+		}
+		var tmp [1]byte
+		c.Read(tmp[:])
+		c.Close()
+
+		go func() {
+			runtime.Gosched()
+			select {}
+		}()
+
+		// Unblock helper goroutines and wait them to finish.
+		wp.Write(tmp[:])
+		wp.Write(tmp[:])
+		close(done)
+		wg.Wait()
+	}()
+
+	for i := 0; i < 3; i++ {
+		buf := new(bytes.Buffer)
+		if err := Start(buf); err != nil {
+			t.Fatalf("failed to start tracing: %v", err)
+		}
+		time.Sleep(time.Millisecond)
+		Stop()
+		saveTrace(t, buf, "TestTraceStressStartStop")
+		trace := buf.Bytes()
+		parseTrace(t, buf)
+		testBrokenTimestamps(t, trace)
+	}
+	<-outerDone
+}
+
+func TestTraceFutileWakeup(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+
+	defer runtime.GOMAXPROCS(runtime.GOMAXPROCS(8))
+	c0 := make(chan int, 1)
+	c1 := make(chan int, 1)
+	c2 := make(chan int, 1)
+	const procs = 2
+	var done sync.WaitGroup
+	done.Add(4 * procs)
+	for p := 0; p < procs; p++ {
+		const iters = 1e3
+		go func() {
+			for i := 0; i < iters; i++ {
+				runtime.Gosched()
+				c0 <- 0
+			}
+			done.Done()
+		}()
+		go func() {
+			for i := 0; i < iters; i++ {
+				runtime.Gosched()
+				<-c0
+			}
+			done.Done()
+		}()
+		go func() {
+			for i := 0; i < iters; i++ {
+				runtime.Gosched()
+				select {
+				case c1 <- 0:
+				case c2 <- 0:
+				}
+			}
+			done.Done()
+		}()
+		go func() {
+			for i := 0; i < iters; i++ {
+				runtime.Gosched()
+				select {
+				case <-c1:
+				case <-c2:
+				}
+			}
+			done.Done()
+		}()
+	}
+	done.Wait()
+
+	Stop()
+	saveTrace(t, buf, "TestTraceFutileWakeup")
+	events, _ := parseTrace(t, buf)
+	// Check that (1) trace does not contain EvFutileWakeup events and
+	// (2) there are no consecutive EvGoBlock/EvGCStart/EvGoBlock events
+	// (we call runtime.Gosched between all operations, so these would be futile wakeups).
+	gs := make(map[uint64]int)
+	for _, ev := range events {
+		switch ev.Type {
+		case trace.EvFutileWakeup:
+			t.Fatalf("found EvFutileWakeup event")
+		case trace.EvGoBlockSend, trace.EvGoBlockRecv, trace.EvGoBlockSelect:
+			if gs[ev.G] == 2 {
+				t.Fatalf("goroutine %v blocked on %v at %v right after start",
+					ev.G, trace.EventDescriptions[ev.Type].Name, ev.Ts)
+			}
+			if gs[ev.G] == 1 {
+				t.Fatalf("goroutine %v blocked on %v at %v while blocked",
+					ev.G, trace.EventDescriptions[ev.Type].Name, ev.Ts)
+			}
+			gs[ev.G] = 1
+		case trace.EvGoStart:
+			if gs[ev.G] == 1 {
+				gs[ev.G] = 2
+			}
+		default:
+			delete(gs, ev.G)
+		}
+	}
+}
+
+func TestTraceCPUProfile(t *testing.T) {
+	if IsEnabled() {
+		t.Skip("skipping because -test.trace is set")
+	}
+
+	cpuBuf := new(bytes.Buffer)
+	if err := pprof.StartCPUProfile(cpuBuf); err != nil {
+		t.Skipf("failed to start CPU profile: %v", err)
+	}
+
+	buf := new(bytes.Buffer)
+	if err := Start(buf); err != nil {
+		t.Fatalf("failed to start tracing: %v", err)
+	}
+
+	dur := 100 * time.Millisecond
+	func() {
+		// Create a region in the execution trace. Set and clear goroutine
+		// labels fully within that region, so we know that any CPU profile
+		// sample with the label must also be eligible for inclusion in the
+		// execution trace.
+		ctx := context.Background()
+		defer StartRegion(ctx, "cpuHogger").End()
+		pprof.Do(ctx, pprof.Labels("tracing", "on"), func(ctx context.Context) {
+			cpuHogger(cpuHog1, &salt1, dur)
+		})
+		// Be sure the execution trace's view, when filtered to this goroutine
+		// via the explicit goroutine ID in each event, gets many more samples
+		// than the CPU profiler when filtered to this goroutine via labels.
+		cpuHogger(cpuHog1, &salt1, dur)
+	}()
+
+	Stop()
+	pprof.StopCPUProfile()
+	saveTrace(t, buf, "TestTraceCPUProfile")
+
+	prof, err := profile.Parse(cpuBuf)
+	if err != nil {
+		t.Fatalf("failed to parse CPU profile: %v", err)
+	}
+	// Examine the CPU profiler's view. Filter it to only include samples from
+	// the single test goroutine. Use labels to execute that filter: they should
+	// apply to all work done while that goroutine is getg().m.curg, and they
+	// should apply to no other goroutines.
+	pprofSamples := 0
+	pprofStacks := make(map[string]int)
+	for _, s := range prof.Sample {
+		if s.Label["tracing"] != nil {
+			var fns []string
+			var leaf string
+			for _, loc := range s.Location {
+				for _, line := range loc.Line {
+					fns = append(fns, fmt.Sprintf("%s:%d", line.Function.Name, line.Line))
+					leaf = line.Function.Name
+				}
+			}
+			// runtime.sigprof synthesizes call stacks when "normal traceback is
+			// impossible or has failed", using particular placeholder functions
+			// to represent common failure cases. Look for those functions in
+			// the leaf position as a sign that the call stack and its
+			// symbolization are more complex than this test can handle.
+			//
+			// TODO: Make the symbolization done by the execution tracer and CPU
+			// profiler match up even in these harder cases. See #53378.
+			switch leaf {
+			case "runtime._System", "runtime._GC", "runtime._ExternalCode", "runtime._VDSO":
+				continue
+			}
+			stack := strings.Join(fns, " ")
+			samples := int(s.Value[0])
+			pprofSamples += samples
+			pprofStacks[stack] += samples
+		}
+	}
+	if pprofSamples == 0 {
+		t.Skipf("CPU profile did not include any samples while tracing was active\n%s", prof)
+	}
+
+	// Examine the execution tracer's view of the CPU profile samples. Filter it
+	// to only include samples from the single test goroutine. Use the goroutine
+	// ID that was recorded in the events: that should reflect getg().m.curg,
+	// same as the profiler's labels (even when the M is using its g0 stack).
+	totalTraceSamples := 0
+	traceSamples := 0
+	traceStacks := make(map[string]int)
+	events, _ := parseTrace(t, buf)
+	var hogRegion *trace.Event
+	for _, ev := range events {
+		if ev.Type == trace.EvUserRegion && ev.Args[1] == 0 && ev.SArgs[0] == "cpuHogger" {
+			// mode "0" indicates region start
+			hogRegion = ev
+		}
+	}
+	if hogRegion == nil {
+		t.Fatalf("execution trace did not identify cpuHogger goroutine")
+	} else if hogRegion.Link == nil {
+		t.Fatalf("execution trace did not close cpuHogger region")
+	}
+	for _, ev := range events {
+		if ev.Type == trace.EvCPUSample {
+			totalTraceSamples++
+			if ev.G == hogRegion.G {
+				traceSamples++
+				var fns []string
+				for _, frame := range ev.Stk {
+					if frame.Fn != "runtime.goexit" {
+						fns = append(fns, fmt.Sprintf("%s:%d", frame.Fn, frame.Line))
+					}
+				}
+				stack := strings.Join(fns, " ")
+				traceStacks[stack]++
+			}
+		}
+	}
+
+	// The execution trace may drop CPU profile samples if the profiling buffer
+	// overflows. Based on the size of profBufWordCount, that takes a bit over
+	// 1900 CPU samples or 19 thread-seconds at a 100 Hz sample rate. If we've
+	// hit that case, then we definitely have at least one full buffer's worth
+	// of CPU samples, so we'll call that success.
+	overflowed := totalTraceSamples >= 1900
+	if traceSamples < pprofSamples {
+		t.Logf("execution trace did not include all CPU profile samples; %d in profile, %d in trace", pprofSamples, traceSamples)
+		if !overflowed {
+			t.Fail()
+		}
+	}
+
+	for stack, traceSamples := range traceStacks {
+		pprofSamples := pprofStacks[stack]
+		delete(pprofStacks, stack)
+		if traceSamples < pprofSamples {
+			t.Logf("execution trace did not include all CPU profile samples for stack %q; %d in profile, %d in trace",
+				stack, pprofSamples, traceSamples)
+			if !overflowed {
+				t.Fail()
+			}
+		}
+	}
+	for stack, pprofSamples := range pprofStacks {
+		t.Logf("CPU profile included %d samples at stack %q not present in execution trace", pprofSamples, stack)
+		if !overflowed {
+			t.Fail()
+		}
+	}
+
+	if t.Failed() {
+		t.Logf("execution trace CPU samples:")
+		for stack, samples := range traceStacks {
+			t.Logf("%d: %q", samples, stack)
+		}
+		t.Logf("CPU profile:\n%v", prof)
+	}
+}
+
+func cpuHogger(f func(x int) int, y *int, dur time.Duration) {
+	// We only need to get one 100 Hz clock tick, so we've got
+	// a large safety buffer.
+	// But do at least 500 iterations (which should take about 100ms),
+	// otherwise TestCPUProfileMultithreaded can fail if only one
+	// thread is scheduled during the testing period.
+	t0 := time.Now()
+	accum := *y
+	for i := 0; i < 500 || time.Since(t0) < dur; i++ {
+		accum = f(accum)
+	}
+	*y = accum
+}
+
+var (
+	salt1 = 0
+)
+
+// The actual CPU hogging function.
+// Must not call other functions nor access heap/globals in the loop,
+// otherwise under race detector the samples will be in the race runtime.
+func cpuHog1(x int) int {
+	return cpuHog0(x, 1e5)
+}
+
+func cpuHog0(x, n int) int {
+	foo := x
+	for i := 0; i < n; i++ {
+		if i%1000 == 0 {
+			// Spend time in mcall, stored as gp.m.curg, with g0 running
+			runtime.Gosched()
+		}
+		if foo > 0 {
+			foo *= foo
+		} else {
+			foo *= foo + 1
+		}
+	}
+	return foo
+}
+
+func saveTrace(t *testing.T, buf *bytes.Buffer, name string) {
+	if !*saveTraces {
+		return
+	}
+	if err := os.WriteFile(name+".trace", buf.Bytes(), 0600); err != nil {
+		t.Errorf("failed to write trace file: %s", err)
+	}
+}