c++ - 子级和父级 C 程序中的 SIGSEGV 处理

Question

下面提到的是我的 C++ 程序。当在任何子进程或父进程内部生成段错误信号时，我想终止所有子进程和父进程。

我从 linux 内核得到 sigterm 信号到达 handle_signal 函数。但我坚持在后来的流程中，调试时我什至看到 gSegSignalRcvd=1 已设置。但是过程控制没有到达子 r 父中的任何 for 循环。

---

#include<iostream>
#include<stdio.h>
#include<sys/types.h> 
#include<unistd.h>
#include<signal.h>

bool gSignalRcvd = 0;
bool gSegSignalRcvd = 0;

pid_t lCid1;
pid_t lCid2;
pid_t lPid;

void handle_signal(int sig)
{
  switch(sig)
  {
    case SIGSEGV:
    {
        gSegSignalRcvd = 1;
        printf("Reecived Signal:%d SegSignal:%d\n", gSignalRcvd, gSegSignalRcvd);
    }
    default:
        printf("Reecived Signal :%d\n",sig);
  };
  gSignalRcvd = 1;
  signal(SIGSEGV, handle_signal);
}

int main()
{
  signal(SIGSEGV, handle_signal);

  lCid1 = fork();

  if(lCid1 < 0)
  {
      printf("Error in child Creation Err:%d\n", lCid1);
      exit(1);
  }
  else if(lCid1 > 0)
  {
      lCid2 = fork();

      if(lCid2 < 0)
      {
          printf("Error in child Creation Err:%d\n", lCid1);
          exit(2);
      }
      else if(lCid2 > 0)
      {
          struct tm * lTimePtr;
          int    lSleepTime=0;
          int    mUploadTime=0;
          int    lCount = 1;
          time_t lTimeObj;

          for(;;)
          {
              lCount = lCount++;
              printf("Received Signal @ Parent Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
              if(gSignalRcvd)
              {
                  if(gSegSignalRcvd)
                  {
                    printf("Received Signal Inside Parent now killing the Process\n");
                    kill(lCid1, SIGTERM);
                    kill(lCid2, SIGTERM);
                    kill(getpid(), SIGTERM);
                  }
              }
              gSignalRcvd = 0;

              printf("Time:%ld tm_min:%d tm_sec:%d UploadTime:%d SleepTime:%d\n", lTimeObj, lTimePtr->tm_min, lTimePtr->tm_sec, mUploadTime, lSleepTime);

              sleep(mUploadTime + lCount);
          }
      }
      else
      {
          int lNumb,lResult;

          for(;;)
          {
              printf("Received Signal @ Child2 Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
              if(gSignalRcvd)
              {
                  if(gSegSignalRcvd)
                  {
                      printf("Received Signal Inside Child2 **************\n");
                      kill(lCid1, SIGTERM);
                      kill(lCid2, SIGTERM);
                      kill(getpid(), SIGTERM);
                  }
              }
              gSignalRcvd = 0;
              printf("Printing the Child2 Value\n");
              lNumb = rand() / 100;

              lResult = lNumb / 2;
              printf("Number:%s Result:%d\n", lNumb, lResult);

              usleep(lNumb);
          }
      }
  }
  else
  {
      for(;;)
      {
          printf("Received Signal @ Child1 Seg:%d Sig%d\n", gSegSignalRcvd, gSignalRcvd);
          if(gSignalRcvd)
          {
              if(gSegSignalRcvd)
              {
                  printf("Received Signal Inside Child1 ---------------\n");
                  kill(lCid1, SIGTERM);
                  kill(lCid2, SIGTERM);
                  kill(getpid(), SIGTERM);
              }
          }
          gSignalRcvd = 0;

          printf("Printing the Child1 Value\n");
          usleep(rand());
      }
  }
  return 0;
}

---

----------- Program OutPut ---------
[scuser@Bilx-Congo-Lab ~]$ ./sigHandle
Received Signal @ Child1 Seg:0 Sig0
Printing the Child1 Value
Received Signal @ Child2 Seg:0 Sig0
Printing the Child2 Value
Number:Reecived Signal:0 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1
Reecived Signal :11
Reecived Signal:1 SegSignal:1

Answer 1

将所有进程放在它们自己的进程组中，然后在任何成员获得 SEGV 时向整个组发送一个 SIGTERM。

在父级中，在任何 fork 之前:

pid_t gPGid;
volatile sig_atomic_t gSegSignalRcvd = 0;

... main() ...
setpgid(0, 0);       // Make new process group, if needed
gPGid = getpgid(0);

然后，在处理程序中，向整个进程组发送信号:

void handler(int sig) {
  if (sig == SIGSEGV) {
    kill(-gPGid, SIGTERM);     // Note the -gPGid here
    _exit(1);                  // We segfaulted - we'd better quit now
  } else if (sig == SIGTERM) {
    gSegSignalRcvd = 1;
  }
  ...
}

在实践中，可能无法达到 _exit()，因为进程组的 SIGTERM 也会中断生成它的程序。

一些注意事项:不要使用 signal() 和在处理程序中重新安装处理程序的过时约定 — 使用 sigaction()反而。不要在处理程序中调用 printf() — that's not safe .您的“标志” bool 值可能应该是 volatile sig_atomic_t类型。