Question

我正在进行一项使用蒙特卡罗模拟的任务，以确定将产生多少随机地址访问。故障直到ULONG_MAX尝试次数。我们被指示创建信号处理程序来处理这些信号SIGSEGV，SIGIINT，SIGTSTP，SIGALRM，SIGUSR1和SIGUSR2。

我有几个关于SIGSEGV，SIGUSR1和SIGUSR2的问题。

对于SIGSEGV，我查看了sigsetjmp和siglongjmp的手册页，但我很困惑这些函数的参数应该做什么。
对于USR信号，方向是： SIGUSR1 / SIGUSR2 - 每当执行10次评估时，然后，当前估计的准确度增加一位精度。例如，在进行了100次评估之后，已知答案在1/100或两位数内精度，并且当执行了1000时，那么答案就在内部已知 1/1000，或3位精度。这个进展将传达给父母（shell）你写的）以下列方式：
- 每次评估的次数超过10次，孩子都应该使用 kill（）命令将SIGUSR1信号发送给父级。（最简单的方法这是设置一个“报告”变量，最初为10，每次都是数量评估与报告变量匹配发送信号并将报告变量相乘由10.）
- 父级现在需要一个信号处理程序来捕获SIGUSR1，并增加一个计数器每次它到来。如果计数器超过了命令行上设置的限制 shell已启动，然后父进程使用kill（）系统调用发送SIGUSR2 向孩子发出信号。（计数器需要在之前的某个时间重置为零启动下一个孩子。）
- 孩子现在需要一个信号处理程序来捕获SIGUSR2。答案应该是与control-C相同，实际上可能是同一个处理程序。

所以，话虽如此，我完全混淆了如何制作/放置这两个USR信号的位置。有人可以帮我从这里出去吗。我非常感谢。这是我一直在研究的代码（减去shell，我确定它工作正常。已经过测试）。

#include <iostream> 
#include <cstdlib> /* srand, rand */ 
#include <time.h>   /* time */
#include <limits.h>
#include <setjmp.h>
#include <signal.h>
using namespace std; 
#define MAXARGS 512

/* Monte Carlo Simulator */
unsigned long int seg_fault = 0; // count for generated segfaults due to attempts 
unsigned long int attempts = 0; // count for evaluations attempted 

// functions
void handler_seg (int sig); 
void handler_int (int sig); 
void handler_tstp (int sig);
void handler_alrm (int arg);    
void handler_usr1 (int sig); 
void handler_usr2 (int sig); 

/* Takes floating point command line argument as max seconds to run before stopping. 
If +, call alarm before starting the for loop*/
/*Generated by CTRL-C, signal handler simply reports the final results and exits */
void handler_int (int sig)
{
    cout << "SIG_INT called" << endl; 
    cout << "Total number of SEG_FAULTS: " << seg_fault << endl; 
    cout << "Total number of evaluations: " << attempts << endl;
    double percent = seg_fault/attempts; 
    cout << "The percentage of seg_fault attempts: " << percent << endl;  
    exit ((int)percent); 
}

/*Generated by CTRL-Z, reports the current results without stopping program, this 
handler doesnt exit, and returns when complete */
void handler_tstp (int sig)
{
    cout << "SIG_TSTP called" << endl;
    cout << "Total number of SEG_FAULTS: " << seg_fault << endl;
    cout << "Total number of evaluations: " << attempts << endl;
    double percent = seg_fault/attempts;
    cout << "The percentage of seg_fault attempts: " << percent << endl;
    return; // can go right back to what you were doing because no errors to report 
}

void handler_seg (int sig)
{
    seg_fault++; 
    attempts++;
    // return of the handler if eval counter hasnt reached the limit ulong_max
    if (attempts != ULONG_MAX)
        siglongjmp(); // fixes the error of seg_fault infinite loop 
    else 
    {
        cout << "SIG_INT called" << endl; 
        cout << "Total number of SEG_FAULTS: " << seg_fault << endl; 
        cout << "Total number of evaluations: " << attempts << endl;
        double percent = seg_fault/attempts; 
        cout << "The percentage of seg_fault attempts: " << percent << endl;  
        exit ((int)percent); 
    }
}

int main (int argc, char* argv[], char **envp)
{
    srand (time(NULL)); 
    int count = 0;
    char *cargs[MAXARGS];
    int alrmReq = 0; 

// need to parse any command line arguments that are present 
for (int i=0 ; i<argc ; i++)
{
    cout << argv[i] << endl; 
    cargs[i] = argv[i];
    if (i == argc-1)
        alrmReq = atoi(argv[i]); // set the alarm value 
}

// Set up signal handlers to catch and respond to certain signals 
signal (SIGSEGV, handler_seg);

// for loop to generate and test random addresses using global eval 
// counter for the loop counter
 if (alrmReq > 0)
{
    alarm (alrmReq); 
    signal (SIGALRM, handler_alrm); 
}

 int* address_ptr = NULL; // initialization only occurs for the first run in a loop 
 int temp = 0; 
 int report = 10;
for (attempts=0; attempts<100 ; attempts++) // ULONG_MAX
{
    sigsetjmp(); // remembers the context at the beginnging of the loop
    attempts++; 
    address_ptr = (int*)rand(); // possibly not all the mem locations
    // attempt to read from possible seg_fault location 
    temp = *address_ptr; // for seg fault returns back to redo instruction that caused the fault

    // check if attempts is a power of 10
    if (attempts == report)
    {
        //child use the kill command to send SIGUSR1 signal to parent 
        signal (SIGUSR1, handler_usr1); 
        report = report*10; 
    }
}   

// successfully completed the for loop 
cout << "Successfully completed the for loop" << endl; 
cout << "Total number of SEG_FAULTS: " << seg_fault << endl; 
cout << "Total number of evaluations: " << attempts << endl;
double percent = seg_fault/attempts; 
cout << "The percentage of seg_fault attempts: " << percent << endl;  
exit ((int)percent); 
}

C / C ++中的信号 - 使个人shell发送/接收信号程序

0 个答案: