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// Copyright 2020 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
// +build !plan9,!windows
package main
// This is for issue #42207.
// During a call to needm we could get a SIGCHLD signal
// which would itself call needm, causing a deadlock.
/*
#include <signal.h>
#include <pthread.h>
#include <sched.h>
#include <unistd.h>
extern void GoNeedM();
#define SIGNALERS 10
static void* needmSignalThread(void* p) {
pthread_t* pt = (pthread_t*)(p);
int i;
for (i = 0; i < 100; i++) {
if (pthread_kill(*pt, SIGCHLD) < 0) {
return NULL;
}
usleep(1);
}
return NULL;
}
// We don't need many calls, as the deadlock is only likely
// to occur the first couple of times that needm is called.
// After that there will likely be an extra M available.
#define CALLS 10
static void* needmCallbackThread(void* p) {
int i;
for (i = 0; i < SIGNALERS; i++) {
sched_yield(); // Help the signal threads get started.
}
for (i = 0; i < CALLS; i++) {
GoNeedM();
}
return NULL;
}
static void runNeedmSignalThread() {
int i;
pthread_t caller;
pthread_t s[SIGNALERS];
pthread_create(&caller, NULL, needmCallbackThread, NULL);
for (i = 0; i < SIGNALERS; i++) {
pthread_create(&s[i], NULL, needmSignalThread, &caller);
}
for (i = 0; i < SIGNALERS; i++) {
pthread_join(s[i], NULL);
}
pthread_join(caller, NULL);
}
*/
import "C"
import (
"fmt"
"os"
"time"
)
func init() {
register("NeedmDeadlock", NeedmDeadlock)
}
//export GoNeedM
func GoNeedM() {
}
func NeedmDeadlock() {
// The failure symptom is that the program hangs because of a
// deadlock in needm, so set an alarm.
go func() {
time.Sleep(5 * time.Second)
fmt.Println("Hung for 5 seconds")
os.Exit(1)
}()
C.runNeedmSignalThread()
fmt.Println("OK")
}
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