1 files changed, 89 insertions, 0 deletions
diff --git a/src/runtime/testdata/testprogcgo/pprof_callback.go b/src/runtime/testdata/testprogcgo/pprof_callback.go
new file mode 100644
index 0000000..fd87eb8
--- /dev/null
+++ b/src/runtime/testdata/testprogcgo/pprof_callback.go
@@ -0,0 +1,89 @@
+// Copyright 2022 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.
+
+//go:build !plan9 && !windows
+
+package main
+
+// Make many C-to-Go callback while collecting a CPU profile.
+//
+// This is a regression test for issue 50936.
+
+/*
+#include <unistd.h>
+
+void goCallbackPprof();
+
+static void callGo() {
+	// Spent >20us in C so this thread is eligible for sysmon to retake its
+	// P.
+	usleep(50);
+	goCallbackPprof();
+}
+*/
+import "C"
+
+import (
+	"fmt"
+	"os"
+	"runtime"
+	"runtime/pprof"
+	"time"
+)
+
+func init() {
+	register("CgoPprofCallback", CgoPprofCallback)
+}
+
+//export goCallbackPprof
+func goCallbackPprof() {
+	// No-op. We want to stress the cgocall and cgocallback internals,
+	// landing as many pprof signals there as possible.
+}
+
+func CgoPprofCallback() {
+	// Issue 50936 was a crash in the SIGPROF handler when the signal
+	// arrived during the exitsyscall following a cgocall(back) in dropg or
+	// execute, when updating mp.curg.
+	//
+	// These are reachable only when exitsyscall finds no P available. Thus
+	// we make C calls from significantly more Gs than there are available
+	// Ps. Lots of runnable work combined with >20us spent in callGo makes
+	// it possible for sysmon to retake Ps, forcing C calls to go down the
+	// desired exitsyscall path.
+	//
+	// High GOMAXPROCS is used to increase opportunities for failure on
+	// high CPU machines.
+	const (
+		P = 16
+		G = 64
+	)
+	runtime.GOMAXPROCS(P)
+
+	f, err := os.CreateTemp("", "prof")
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+	defer f.Close()
+
+	if err := pprof.StartCPUProfile(f); err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		os.Exit(2)
+	}
+
+	for i := 0; i < G; i++ {
+		go func() {
+			for {
+				C.callGo()
+			}
+		}()
+	}
+
+	time.Sleep(time.Second)
+
+	pprof.StopCPUProfile()
+
+	fmt.Println("OK")
+}