Run an infinite loop at max/FIFO thread priority. OS: Linux, w/ pthread.

peg_cpu.cpp

#include <pthread.h>
#include <sched.h>
#include <iostream>

void infLoop() {
    int i = 0;
    while (true) {
        i = (i + 1) % 1024;
    }
}

void set_realtime_priority() {
  int ret;

  // We'll operate on the currently running thread.
  pthread_t this_thread = pthread_self();
  // struct sched_param is used to store the scheduling priority
  struct sched_param params;

  // We'll set the priority to the maximum.
  params.sched_priority = sched_get_priority_max(SCHED_FIFO);
  std::cout << "Trying to set thread realtime prio = " << params.sched_priority << std::endl;

  // Attempt to set thread real-time priority to the SCHED_FIFO policy
  ret = pthread_setschedparam(this_thread, SCHED_FIFO, &params);
  if (ret != 0) {
    // Print the error
    std::cout << "Unsuccessful in setting thread realtime prio" << std::endl;
    return;
  }

  // Now verify the change in thread priority
  int policy = 0;
  ret = pthread_getschedparam(this_thread, &policy, &params);
  if (ret != 0) {
    std::cout << "Couldn't retrieve real-time scheduling paramers" << std::endl;
    return;
  }

  // Check the correct policy was applied
  if(policy != SCHED_FIFO) {
    std::cout << "Scheduling is NOT SCHED_FIFO!" << std::endl;
  } else {
    std::cout << "SCHED_FIFO OK" << std::endl;
  }

  // Print thread scheduling priority
  std::cout << "Thread priority is " << params.sched_priority << std::endl;
  std::cout << "Looping!";

  infLoop();
}

int main() {
  set_realtime_priority();
}