runtime: uphold goroutine profile invariants in coroswitch

Goroutine profiles require checking in with the profiler before any
goroutine starts running. coroswitch is a place where a goroutine may
start running, but where we do not check in with the profiler, which
leads to crashes. Fix this by checking in with the profiler the same way
execute does.

Fixes #69998.

Change-Id: Idef6dd31b70a73dd1c967b56c307c7a46a26ba73
Reviewed-on: https://go-review.googlesource.com/c/go/+/622016
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

1 files changed, 45 insertions, 0 deletions

diff --git a/src/runtime/pprof/pprof_test.go b/src/runtime/pprof/pprof_test.go
index e9f287df60..19641f62aa 100644
--- a/src/runtime/pprof/pprof_test.go
+++ b/src/runtime/pprof/pprof_test.go
@@ -15,6 +15,7 @@ import (
 	"internal/syscall/unix"
 	"internal/testenv"
 	"io"
+	"iter"
 	"math"
 	"math/big"
 	"os"
@@ -1784,6 +1785,50 @@ func TestGoroutineProfileConcurrency(t *testing.T) {
 	}
 }
 
+// Regression test for #69998.
+func TestGoroutineProfileCoro(t *testing.T) {
+	testenv.MustHaveParallelism(t)
+
+	goroutineProf := Lookup("goroutine")
+
+	// Set up a goroutine to just create and run coroutine goroutines all day.
+	iterFunc := func() {
+		p, stop := iter.Pull2(
+			func(yield func(int, int) bool) {
+				for i := 0; i < 10000; i++ {
+					if !yield(i, i) {
+						return
+					}
+				}
+			},
+		)
+		defer stop()
+		for {
+			_, _, ok := p()
+			if !ok {
+				break
+			}
+		}
+	}
+	var wg sync.WaitGroup
+	done := make(chan struct{})
+	wg.Add(1)
+	go func() {
+		defer wg.Done()
+		for {
+			iterFunc()
+			select {
+			case <-done:
+			default:
+			}
+		}
+	}()
+
+	// Take a goroutine profile. If the bug in #69998 is present, this will crash
+	// with high probability. We don't care about the output for this bug.
+	goroutineProf.WriteTo(io.Discard, 1)
+}
+
 func BenchmarkGoroutine(b *testing.B) {
 	withIdle := func(n int, fn func(b *testing.B)) func(b *testing.B) {
 		return func(b *testing.B) {