VILLASnode/common/lib/task.cpp

/* Run tasks periodically.
 *
 * Author: Steffen Vogel <post@steffenvogel.de>
 * SPDX-FileCopyrightText: 2014-2023 Institute for Automation of Complex Power Systems, RWTH Aachen University
 * SPDX-License-Identifier: Apache-2.0
 */

#include <cerrno>
#include <ctime>
#include <unistd.h>

#include <villas/exceptions.hpp>
#include <villas/task.hpp>
#include <villas/timing.hpp>
#include <villas/utils.hpp>

using namespace villas;

#if PERIODIC_TASK_IMPL == TIMERFD
#include <sys/timerfd.h>
#endif // PERIODIC_TASK_IMPL

Task::Task(int clk) : clock(clk) {
#if PERIODIC_TASK_IMPL == TIMERFD
  fd = timerfd_create(clock, 0);
  if (fd < 0)
    throw SystemError("Failed to create timerfd");
#elif PERIODIC_TASK_IMPL == RDTSC
  int ret = tsc_init(&tsc);
  if (ret)
    return ret;
#endif // PERIODIC_TASK_IMPL
}

void Task::setTimeout(double to) {
  struct timespec now;

  clock_gettime(clock, &now);

  struct timespec timeout = time_from_double(to);
  struct timespec next = time_add(&now, &timeout);

  setNext(&next);
}

void Task::setNext(const struct timespec *nxt) {

#if PERIODIC_TASK_IMPL != RDTSC
  next = *nxt;

#if PERIODIC_TASK_IMPL == TIMERFD
  int ret;
  struct itimerspec its = {.it_interval = (struct timespec){0, 0},
                           .it_value = next};

  ret = timerfd_settime(fd, TFD_TIMER_ABSTIME, &its, nullptr);
  if (ret)
    throw SystemError("Failed to set timerfd");
#endif // PERIODIC_TASK_IMPL == TIMERFD
#endif // PERIODIC_TASK_IMPL != RDTSC
}

void Task::setRate(double rate) {
#if PERIODIC_TASK_IMPL == RDTSC
  period = tsc_rate_to_cycles(&tsc, rate);
  next = tsc_now(&tsc) + period;
#else
  // A rate of 0 will disarm the timer
  period = rate ? time_from_double(1.0 / rate) : (struct timespec){0, 0};

#if PERIODIC_TASK_IMPL == CLOCK_NANOSLEEP || PERIODIC_TASK_IMPL == NANOSLEEP
  struct timespec now, next;

  clock_gettime(clock, &now);

  next = time_add(&now, &period);

  return setNext(&next);
#elif PERIODIC_TASK_IMPL == TIMERFD
  int ret;
  struct itimerspec its = {.it_interval = period, .it_value = period};

  ret = timerfd_settime(fd, 0, &its, nullptr);
  if (ret)
    throw SystemError("Failed to set timerfd");
#endif // PERIODIC_TASK_IMPL
#endif // PERIODIC_TASK_IMPL == RDTSC
}

Task::~Task() {
#if PERIODIC_TASK_IMPL == TIMERFD
  close(fd);
#endif
}

uint64_t Task::wait() {
  uint64_t runs;

#if PERIODIC_TASK_IMPL == CLOCK_NANOSLEEP || PERIODIC_TASK_IMPL == NANOSLEEP
  int ret;
  struct timespec now;

  ret = clock_gettime(clock, &now);
  if (ret)
    return ret;

  for (runs = 0; time_cmp(&next, &now) < 0; runs++)
    next = time_add(&next, &period);

#if PERIODIC_TASK_IMPL == CLOCK_NANOSLEEP
  do {
    ret = clock_nanosleep(clock, TIMER_ABSTIME, &next, nullptr);
  } while (ret == EINTR);
#elif PERIODIC_TASK_IMPL == NANOSLEEP
  struct timespec req, rem = time_diff(&now, &next);

  do {
    req = rem;
    ret = nanosleep(&req, &rem);
  } while (ret < 0 && errno == EINTR);
#endif
  if (ret)
    return 0;

  ret = clock_gettime(clock, &now);
  if (ret)
    return ret;

  for (; time_cmp(&next, &now) < 0; runs++)
    next = time_add(&next, &period);
#elif PERIODIC_TASK_IMPL == TIMERFD
  int ret;

  ret = read(fd, &runs, sizeof(runs));
  if (ret < 0)
    return 0;
#elif PERIODIC_TASK_IMPL == RDTSC
  uint64_t now;

  do {
    now = tsc_now(&tsc);
  } while (now < next);

  for (runs = 0; next < now; runs++)
    next += period;
#else
#error "Invalid period task implementation"
#endif

  return runs;
}

void Task::stop() {
#if PERIODIC_TASK_IMPL == TIMERFD
  int ret;
  struct itimerspec its = {.it_interval = (struct timespec){0, 0},
                           .it_value = (struct timespec){0, 0}};

  ret = timerfd_settime(fd, 0, &its, nullptr);
  if (ret)
    throw SystemError("Failed to disarm timerfd");
#endif // PERIODIC_TASK_IMPL == TIMERFD
}

int Task::getFD() const {
#if PERIODIC_TASK_IMPL == TIMERFD
  return fd;
#else
  return -1;
#endif
}