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// 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/pprof"
"runtime"
"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")
}
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