Question

我试图实现检查点功能来检查进程。我通过分配子进程来做到这一点。但是我需要在开始时暂停子进程。稍后，我们可以通过取消暂停子进程并使父进程自行从检查点重新启动。

以下是我为checkpoint和restart_from_checkpoint撰写的代码以及如何调用它们的示例。

#include <stdio.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <sys/wait.h>

pid_t checkpoint();
void restart_from_checkpoint( pid_t pid );

int main( int argc, char *argv[] )
{
  int i;
  pid_t child_pid;
  pid_t parent_pid = getpid();

  for( i = 0; i < 10; i++ )
  {
    if ( i == 4 )
    {
      printf( "%6s: Checkpointing!\n", (getpid() == parent_pid)? "parent":"child" );
      child_pid = checkpoint();
    }

    if ( i == 7 )
    {
      printf( "%6s: Restarting!\n", (getpid() == parent_pid)? "parent":"child" );
      restart_from_checkpoint( child_pid );
    }

    printf( "%6s: i = %d\n", (getpid() == parent_pid)? "parent":"child", i );
  }

  return 0;
}

pid_t checkpoint()
{
    pid_t pid;
    int wait_val;

    switch (pid=fork()) 
    {
    case -1: 
        perror("fork"); 
        break;
    case 0:         // child process starts
        ptrace(PTRACE_TRACEME,0,0,0);
        raise( SIGTRAP ); // Note that this is the solution to first part
                              // of the question, which I added after
                              // asking this question.
        break;  // child process ends
    default:        // parent process starts
        wait(&wait_val);
        return pid;
    }
}

void restart_from_checkpoint( pid_t pid )
{
    ptrace(PTRACE_CONT, pid, NULL, NULL);
    wait(NULL); // I'm just waiting here, but actually 
                //  I need to kill the calling process.
}

我在调用ptrace(PTRACE_TRACEME,0,0,0)后不知道如何停止子进程。其次，在让孩子继续restart_from_checkpoint时，我不知道如何杀死父进程。

最好的方法是使用ptrace参数来启动分叉流程，然后以PTRACE_CONT开始。不幸的是，PTRACE_TRACEME仅在exec函数调用停止。

Answer 1

您可以使用IPC信号量或SIGNAL USR1 ......

Answer 2

好的，我找到了解决方案。它现在工作得很好。以下是您感兴趣的人的代码。

#include <stdio.h>
#include <unistd.h>
#include <sys/ptrace.h>
#include <sys/wait.h>
#include <stdlib.h>

pid_t checkpoint();
void restart_from_checkpoint( pid_t pid );

int main( int argc, char *argv[] )
{
  int i;
  pid_t child_pid;
  pid_t parent_pid = getpid();

  for( i = 0; i < 10; i++ )
  {
    if ( i == 4 )
    {
      printf( "%6s: Checkpointing!\n", (getpid() == parent_pid)? "parent":"child" );
      child_pid = checkpoint();
    }

    if ( i == 7 && ( getpid() == parent_pid ) )
    {
      printf( "%6s: Restarting!\n", (getpid() == parent_pid)? "parent":"child" );
      restart_from_checkpoint( child_pid );
    }

    printf( "%6s: i = %d\n", (getpid() == parent_pid)? "parent":"child", i );
  }

  return 0;
}

pid_t checkpoint()
{
    pid_t pid;
    int wait_val;

    switch (pid=fork()) 
    {
    case -1: 
        perror("fork"); 
        break;
    case 0:         // child process starts
        ptrace(PTRACE_TRACEME,0,0,0);
        raise(SIGTRAP);
        break;  // child process ends
    default:        // parent process starts
        wait(&wait_val);
        return pid;
    }
}

void restart_from_checkpoint( pid_t pid )
{
    ptrace(PTRACE_CONT, pid, NULL, NULL);
    ptrace(PTRACE_DETACH, pid, NULL, NULL);
    exit( 1 );
}

在开始时停止子进程

2 个答案: