runtime: record parent goroutine ID, and print it in stack traces

Fixes #38651

Change-Id: Id46d684ee80e208c018791a06c26f304670ed159
Reviewed-on: https://go-review.googlesource.com/c/go/+/435337
Run-TryBot: Nick Ripley <nick.ripley@datadoghq.com>
Reviewed-by: Ethan Reesor <ethan.reesor@gmail.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/runtime/export_test.go

@@ -540,6 +540,10 @@ func Getg() *G {
 	return getg()
 }
 
+func Goid() uint64 {
+	return getg().goid
+}
+
 func GIsWaitingOnMutex(gp *G) bool {
 	return readgstatus(gp) == _Gwaiting && gp.waitreason.isMutexWait()
 }

src/runtime/proc.go

@@ -4283,6 +4283,7 @@ func newproc1(fn *funcval, callergp *g, callerpc uintptr) *g {
 	newg.sched.pc = abi.FuncPCABI0(goexit) + sys.PCQuantum // +PCQuantum so that previous instruction is in same function
 	newg.sched.g = guintptr(unsafe.Pointer(newg))
 	gostartcallfn(&newg.sched, fn)
+	newg.parentGoid = callergp.goid
 	newg.gopc = callerpc
 	newg.ancestors = saveAncestors(callergp)
 	newg.startpc = fn.fn

src/runtime/proc_test.go

@@ -415,7 +415,10 @@ func TestNumGoroutine(t *testing.T) {
 		n := runtime.NumGoroutine()
 		buf = buf[:runtime.Stack(buf, true)]
 
-		nstk := strings.Count(string(buf), "goroutine ")
+		// To avoid double-counting "goroutine" in "goroutine $m [running]:"
+		// and "created by $func in goroutine $n", remove the latter
+		output := strings.ReplaceAll(string(buf), "in goroutine", "")
+		nstk := strings.Count(output, "goroutine ")
 		if n == nstk {
 			break
 		}

src/runtime/runtime2.go

@@ -479,6 +479,7 @@ type g struct {
 	sigcode0       uintptr
 	sigcode1       uintptr
 	sigpc          uintptr
+	parentGoid     uint64          // goid of goroutine that created this goroutine
 	gopc           uintptr         // pc of go statement that created this goroutine
 	ancestors      *[]ancestorInfo // ancestor information goroutine(s) that created this goroutine (only used if debug.tracebackancestors)
 	startpc        uintptr         // pc of goroutine function

src/runtime/sizeof_test.go

@@ -21,7 +21,7 @@ func TestSizeof(t *testing.T) {
 		_32bit uintptr // size on 32bit platforms
 		_64bit uintptr // size on 64bit platforms
 	}{
-		{runtime.G{}, 240, 392},   // g, but exported for testing
+		{runtime.G{}, 248, 400},   // g, but exported for testing
 		{runtime.Sudog{}, 56, 88}, // sudog, but exported for testing
 	}
 

src/runtime/traceback.go

@@ -701,12 +701,16 @@ func printcreatedby(gp *g) {
 	pc := gp.gopc
 	f := findfunc(pc)
 	if f.valid() && showframe(f, gp, false, funcID_normal, funcID_normal) && gp.goid != 1 {
-		printcreatedby1(f, pc)
+		printcreatedby1(f, pc, gp.parentGoid)
 	}
 }
 
-func printcreatedby1(f funcInfo, pc uintptr) {
+func printcreatedby1(f funcInfo, pc uintptr, goid uint64) {
-	print("created by ", funcname(f), "\n")
+	print("created by ", funcname(f))
+	if goid != 0 {
+		print(" in goroutine ", goid)
+	}
+	print("\n")
 	tracepc := pc // back up to CALL instruction for funcline.
 	if pc > f.entry() {
 		tracepc -= sys.PCQuantum
@@ -806,7 +810,9 @@ func printAncestorTraceback(ancestor ancestorInfo) {
 	// Show what created goroutine, except main goroutine (goid 1).
 	f := findfunc(ancestor.gopc)
 	if f.valid() && showfuncinfo(f, false, funcID_normal, funcID_normal) && ancestor.goid != 1 {
-		printcreatedby1(f, ancestor.gopc)
+		// In ancestor mode, we'll already print the goroutine ancestor.
+		// Pass 0 for the goid parameter so we don't print it again.
+		printcreatedby1(f, ancestor.gopc, 0)
 	}
 }
 

src/runtime/traceback_test.go

@@ -6,9 +6,12 @@ package runtime_test
 
 import (
 	"bytes"
+	"fmt"
 	"internal/abi"
 	"internal/testenv"
 	"runtime"
+	"strings"
+	"sync"
 	"testing"
 )
 
@@ -420,3 +423,23 @@ func testTracebackArgs11b(a, b, c, d int32) int {
 func poisonStack() [20]int {
 	return [20]int{-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1}
 }
+
+func TestTracebackParentChildGoroutines(t *testing.T) {
+	parent := fmt.Sprintf("goroutine %d", runtime.Goid())
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		buf := make([]byte, 1<<10)
+		// We collect the stack only for this goroutine (by passing
+		// false to runtime.Stack). We expect to see the current
+		// goroutine ID, and the parent goroutine ID in a message like
+		// "created by ... in goroutine N".
+		stack := string(buf[:runtime.Stack(buf, false)])
+		child := fmt.Sprintf("goroutine %d", runtime.Goid())
+		if !strings.Contains(stack, parent) || !strings.Contains(stack, child) {
+			t.Errorf("did not see parent (%s) and child (%s) IDs in stack, got %s", parent, child, stack)
+		}
+	}()
+	wg.Wait()
+}