Question

下面提到的是我的C ++程序。我想要杀死所有的儿童和儿童父进程，当在子进程或父进程内部生成分段错误信号时。

我从linux内核sigterm信号到达handle_signal函数。但我在以后的流程中坚持，当调试时我甚至看到gSegSignalRcvd = 1被设置。但是进程控制没有到达子r父级中的任何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

您的问题是，一旦信号被处理，流程将返回到有问题的代码，再次产生分段错误。

更简单的方法是让信号处理程序执行子项的kill()，然后exit()或abort()。

或者，siglongjmp()或将上下文切换到安全位置（如this answer所示，但我建议您使用makecontext()而不是处理特定于平台的寄存器。）。

Answer 2

将所有进程放在他们自己的进程组中，然后在任何成员获得SEGV时将SIGTERM发送给整个组。

在父母中，在任何分叉之前：

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，发出整个进程组的信号：

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;
  }
  ...
}

一些评论：不要使用signal()以及在处理程序中重新安装处理程序的日期约定 - 请改用sigaction()。不要在处理程序中调用printf() - that's not safe。你的“旗帜”布尔可能应该是volatile sig_atomic_t种类型。

SIGSEGV处理儿童和儿童父C程序

2 个答案: