libgo/go/runtime/testdata/testprogcgo/needmdeadlock.go

   1 // Copyright 2020 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build !plan9,!windows
   6
   7 package main
   8
   9 // This is for issue #42207.
  10 // During a call to needm we could get a SIGCHLD signal
  11 // which would itself call needm, causing a deadlock.
  12
  13 /*
  14 #include <signal.h>
  15 #include <pthread.h>
  16 #include <sched.h>
  17 #include <unistd.h>
  18
  19 extern void GoNeedM();
  20
  21 #define SIGNALERS 10
  22
  23 static void* needmSignalThread(void* p) {
  24         pthread_t* pt = (pthread_t*)(p);
  25         int i;
  26
  27         for (i = 0; i < 100; i++) {
  28                 if (pthread_kill(*pt, SIGCHLD) < 0) {
  29                         return NULL;
  30                 }
  31                 usleep(1);
  32         }
  33         return NULL;
  34 }
  35
  36 // We don't need many calls, as the deadlock is only likely
  37 // to occur the first couple of times that needm is called.
  38 // After that there will likely be an extra M available.
  39 #define CALLS 10
  40
  41 static void* needmCallbackThread(void* p) {
  42         int i;
  43
  44         for (i = 0; i < SIGNALERS; i++) {
  45                 sched_yield(); // Help the signal threads get started.
  46         }
  47         for (i = 0; i < CALLS; i++) {
  48                 GoNeedM();
  49         }
  50         return NULL;
  51 }
  52
  53 static void runNeedmSignalThread() {
  54         int i;
  55         pthread_t caller;
  56         pthread_t s[SIGNALERS];
  57
  58         pthread_create(&caller, NULL, needmCallbackThread, NULL);
  59         for (i = 0; i < SIGNALERS; i++) {
  60                 pthread_create(&s[i], NULL, needmSignalThread, &caller);
  61         }
  62         for (i = 0; i < SIGNALERS; i++) {
  63                 pthread_join(s[i], NULL);
  64         }
  65         pthread_join(caller, NULL);
  66 }
  67 */
  68 import "C"
  69
  70 import (
  71         "fmt"
  72         "os"
  73         "time"
  74 )
  75
  76 func init() {
  77         register("NeedmDeadlock", NeedmDeadlock)
  78 }
  79
  80 //export GoNeedM
  81 func GoNeedM() {
  82 }
  83
  84 func NeedmDeadlock() {
  85         // The failure symptom is that the program hangs because of a
  86         // deadlock in needm, so set an alarm.
  87         go func() {
  88                 time.Sleep(5 * time.Second)
  89                 fmt.Println("Hung for 5 seconds")
  90                 os.Exit(1)
  91         }()
  92
  93         C.runNeedmSignalThread()
  94         fmt.Println("OK")
  95 }