#! /usr/bin/env stap
/*
 * watchdog.stp
 * usage: stap watchdog.stp start_event stop_event time_ms
 */

global active, count

function trigger(p:long) { 
  /* may want to change the action here */
  event=sprintf("/usr/bin/pstack %d", p);
  system(event);
}

probe $1 { active[pid()]=1 }
probe $2 { delete active[pid()]; delete count[pid()]}

probe timer.ms($3) {
  foreach (p in active) {
    count[p]++
    if (count[p] == 2) 
      trigger(p)
  }
}