当我跟踪此代码时

void printMsg();

int main() {
  signal(SIGPROF,printMsg);

  struct itimerval tick;
  memset(&tick,sizeof(tick));

  tick.it_value.tv_sec = 1;  // sec
  tick.it_value.tv_usec = 0; // micro sec.
  tick.it_interval.tv_sec = 0;
  tick.it_interval.tv_usec = 0;

  setitimer(ITIMER_PROF,&tick,NULL);

  while(1) {
    ;
  }

  return 0;
}

void printMsg() {
    printf("%s","Hello World!!\n");
}

1秒后我收到了SIGPROF信号

...
05:54:10 setitimer(ITIMER_PROF,{it_interval={0,0},it_value={1,0}},NULL) = 0
05:54:11 --- SIGPROF {si_signo=SIGPROF,si_code=SI_KERNEL} ---
...

但是，当我在write(2,"",0)中添加诸如read(2,0)或while(1)的系统调用并再次跟踪时，似乎无法触发SIGPROF。但是，time(0)中的while(1)可以正确触发SIGPROF。

顺便说一句，我使用此代码模拟以下PHP脚本，该脚本忽略了PHP-FPM SAPI下的时间限制，

<?php
set_time_limit(5);  // PHP uses setitimer(ITIMER_PROF) to implement this function
while (true) {
    flush();       // PHP uses write(<fd>,0) to implement this function
}