c - 如何在循环中设置信号检查？

Question

在 createProcess(pid_t pidArray[]) 函数中我创建了新进程，如果它是子进程我打印它。但是在 while 循环中我每次都检查 killFlag，我的程序没有效率。我该如何解决这个问题？感谢您的任何帮助。在我的程序中，您可以通过按 + 添加进程或按 - 删除它，或者按 q 退出。

这是我的代码:

#include <ncurses.h> 
#include <unistd.h> 
#include <sys/wait.h> 
#include <signal.h> 
#include <string.h> 
#include <stdlib.h> 

bool printAllowed = false; 
bool killFlag = true; 
bool flag = false; 
int processesCount = 0; 
int currentProcessNumber = 0; 
static const char *colors[] = { "\x1B[0m", "\x1B[31m","\x1B[32m","\x1B[33m","\x1B[34m","\x1B[35m","\x1B[36m","\x1B[37m" }; 

struct sigaction printSignal, killSignal; 

void allowPrint(int sign){ 
  printAllowed = true; 
} 

void setKillFlag(int sign){ 
  killFlag = true; 
} 

int createProcess(pid_t pidArray[]){ 

  if(processesCount > 100) return 1; 

  pidArray[processesCount] = fork(); 
  processesCount++; 

  switch(pidArray[processesCount - 1]){ 

    case 0:{ 
      killFlag = false; 
      char buff[255]; 
      int colorNumber = (processesCount > 7)? 0 : processesCount; 
      sprintf(buff,"%sProcess %d || ", colors[colorNumber], processesCount); 
      while(!killFlag) { 
        usleep(10000); 
        if(printAllowed){ 
          for(int i = 0; i < strlen(buff); i++){ 
            if(killFlag) { return -1;}; 
            printf("%c", buff[i]); 
            refresh(); 
            usleep(50000); 
          } 
          printAllowed = false; 
          // signal to parent that process stop print
          kill(getppid(), SIGUSR2); 
        } 
      } 
      return -1; 
    } 

    case -1: printf("%sError!", colors[1]); return 1; 

    default:  return 1; 
  } 
} 

bool killProcess(pid_t pidArray[]){ 
  if (processesCount <= 0) return 1; 

  processesCount--; 
  // stop last child process
  kill(pidArray[processesCount], SIGUSR2); 
  waitpid(pidArray[processesCount], NULL, NULL); 
  // if the process that printing now stopped
  if (currentProcessNumber >= processesCount){ 
    currentProcessNumber = 0; // start from beginning
    flag = true;  // flag last process by number
    killFlag = true; // flag of end printing current process
  } 

  return 1; 
} 

int controlProcesses(pid_t pidArray[]){ 
  halfdelay(1); 
  switch((char)getchar()){ 
  case '=': return createProcess(pidArray); 
  case '-': return killProcess(pidArray); 
  case 'q': return 0; 
  default: return 1; 
  } 
} 

void killAllProcesses(pid_t pidArray[]){ 
  if(pidArray[--processesCount] != 0) 
    for( ;processesCount >= 0; processesCount--){ 
      kill(pidArray[processesCount],SIGUSR2); 
      waitpid(pidArray[processesCount],NULL,NULL); 
    } 
} 

int main(){ 

  initscr(); 
  clear(); 
  noecho(); 
  refresh(); 


  printSignal.sa_handler = allowPrint; 
  sigaction(SIGUSR1,&printSignal,NULL); 

  killSignal.sa_handler = setKillFlag; 
  sigaction(SIGUSR2,&killSignal,NULL); 

  pid_t pidArray[100]; 

  while(int i = controlProcesses(pidArray)) { 

    if(i == -1) return 0; 


    if(killFlag && processesCount > 0){  // if current process stop printing
      killFlag = false; 
      if(currentProcessNumber >= processesCount - 1) currentProcessNumber = 0; // if the number of current process is last, start from beginning
      else if(!flag) currentProcessNumber++; // else if last stopped process wasn't the last by number go to next process
      flag = false; 
      kill(pidArray[currentProcessNumber], SIGUSR1); // signal to child process start the printing
    } 
    refresh(); 
  } 
  // stop all child processes
  killAllProcesses(pidArray); 

  clear(); 
  endwin(); 

  return 0; 
}

Answer 1

您的 killFlags(和 printAllowed)声明错误。应该声明

volatile sig_atomic_t killFlags, printAllowed;

volatile预选赛真的很重要。否则，编译器会通过假设只能显式更改 killFlags 来优化(它不知道信号处理程序可以随时更改它，因此它可以通过将该变量保存在寄存器中来优化，等等) ...)。

仔细阅读signal(7)手册页。

如果你的循环是轮询 event loop (可能基于 poll(2) ...)您可能会考虑使用特定于 Linux 的 signalfd(2)打电话。