glibc/time/tst-cpuclock1.c

/* Test program for process CPU clocks.
   Copyright (C) 2004-2020 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <errno.h>
#include <signal.h>
#include <stdint.h>
#include <sys/wait.h>
#include <support/timespec.h>

/* This function is intended to rack up both user and system time.  */
static void
chew_cpu (void)
{
  while (1)
    {
      static volatile char buf[4096];
      for (int i = 0; i < 100; ++i)
	for (size_t j = 0; j < sizeof buf; ++j)
	  buf[j] = 0xaa;
      int nullfd = open ("/dev/null", O_WRONLY);
      for (int i = 0; i < 100; ++i)
	for (size_t j = 0; j < sizeof buf; ++j)
	  buf[j] = 0xbb;
      write (nullfd, (char *) buf, sizeof buf);
      close (nullfd);
      if (getppid () == 1)
	_exit (2);
    }
}

static int
do_test (void)
{
  int result = 0;
  clockid_t cl;
  int e;
  pid_t dead_child, child;

  /* Fork a child and let it die, to give us a PID known not be valid
     (assuming PIDs don't wrap around during the test).  */
  {
    dead_child = fork ();
    if (dead_child == 0)
      _exit (0);
    if (dead_child < 0)
      {
	perror ("fork");
	return 1;
      }
    int x;
    if (wait (&x) != dead_child)
      {
	perror ("wait");
	return 2;
      }
  }

  /* POSIX says we should get ESRCH for this.  */
  e = clock_getcpuclockid (dead_child, &cl);
  if (e != ENOSYS && e != ESRCH && e != EPERM)
    {
      printf ("clock_getcpuclockid on dead PID %d => %s\n",
	      dead_child, strerror (e));
      result = 1;
    }

  /* Now give us a live child eating up CPU time.  */
  child = fork ();
  if (child == 0)
    {
      chew_cpu ();
      _exit (1);
    }
  if (child < 0)
    {
      perror ("fork");
      return 1;
    }

  e = clock_getcpuclockid (child, &cl);
  if (e == EPERM)
    {
      puts ("clock_getcpuclockid does not support other processes");
      goto done;
    }
  if (e != 0)
    {
      printf ("clock_getcpuclockid on live PID %d => %s\n",
	      child, strerror (e));
      result = 1;
      goto done;
    }

  const clockid_t child_clock = cl;
  struct timespec res;
  if (clock_getres (child_clock, &res) < 0)
    {
      printf ("clock_getres on live PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
      result = 1;
      goto done;
    }
  printf ("live PID %d clock %lx resolution %ju.%.9ju\n",
	  child, (unsigned long int) child_clock,
	  (uintmax_t) res.tv_sec, (uintmax_t) res.tv_nsec);

  struct timespec before, after;
  if (clock_gettime (child_clock, &before) < 0)
    {
      printf ("clock_gettime on live PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
      result = 1;
      goto done;
    }
  /* Should be close to 0.0.  */
  printf ("live PID %d before sleep => %ju.%.9ju\n",
	  child, (uintmax_t) before.tv_sec, (uintmax_t) before.tv_nsec);

  struct timespec sleeptime = { .tv_nsec = 500000000 };
  if (nanosleep (&sleeptime, NULL) != 0)
    {
      perror ("nanosleep");
      result = 1;
      goto done;
    }

  if (clock_gettime (child_clock, &after) < 0)
    {
      printf ("clock_gettime on live PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
      result = 1;
      goto done;
    }
  /* Should be close to 0.5.  */
  printf ("live PID %d after sleep => %ju.%.9ju\n",
	  child, (uintmax_t) after.tv_sec, (uintmax_t) after.tv_nsec);

  /* The bound values are empirically defined by testing this code over high cpu
     usage and different nice values. Of all the values we keep the 90th
     percentile of values and use those values for our testing allowed range.  */
  struct timespec diff = timespec_sub (support_timespec_normalize (after),
				       support_timespec_normalize (before));
  if (!support_timespec_check_in_range (sleeptime, diff, .9,  1.1))
    {
      printf ("before - after %ju.%.9ju outside reasonable range\n",
	      (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
      result = 1;
    }

  sleeptime.tv_nsec = 100000000;
  e = clock_nanosleep (child_clock, 0, &sleeptime, NULL);
  if (e == EINVAL || e == ENOTSUP || e == ENOSYS)
    {
      printf ("clock_nanosleep not supported for other process clock: %s\n",
	      strerror (e));
    }
  else if (e != 0)
    {
      printf ("clock_nanosleep on other process clock: %s\n", strerror (e));
      result = 1;
    }
  else
    {
      struct timespec afterns;
      if (clock_gettime (child_clock, &afterns) < 0)
	{
	  printf ("clock_gettime on live PID %d clock %lx => %s\n",
		  child, (unsigned long int) child_clock, strerror (errno));
	  result = 1;
	}
      else
	{
        /* The bound values are empirically defined by testing this code over
           high cpu usage and different nice values. Of all the values we keep
           the 90th percentile of values and use those values for our testing
           allowed range.  */
	  diff = timespec_sub (support_timespec_normalize (afterns),
			       support_timespec_normalize (after));
	  if (!support_timespec_check_in_range (sleeptime, diff, .9, 1.2))
	    {
	      printf ("nanosleep time %ju.%.9ju outside reasonable range\n",
		      (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
	      result = 1;
	    }
	}
    }

  if (kill (child, SIGKILL) != 0)
    {
      perror ("kill");
      result = 2;
      goto done;
    }

  /* Wait long enough to let the child finish dying.  */

  sleeptime.tv_nsec = 200000000;
  if (nanosleep (&sleeptime, NULL) != 0)
    {
      perror ("nanosleep");
      result = 1;
      goto done;
    }

  struct timespec dead;
  if (clock_gettime (child_clock, &dead) < 0)
    {
      printf ("clock_gettime on dead PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
      result = 1;
      goto done;
    }
  /* Should be close to 0.6.  */
  printf ("dead PID %d => %ju.%.9ju\n",
	  child, (uintmax_t) dead.tv_sec, (uintmax_t) dead.tv_nsec);
  /* The bound values are empirically defined by testing this code over high cpu
     usage and different nice values. Of all the values we keep the 90th
     percentile of values and use those values for our testing allowed range.  */
  diff = timespec_sub (support_timespec_normalize (dead),
		       support_timespec_normalize (after));
  sleeptime.tv_nsec = 100000000;
  if (!support_timespec_check_in_range (sleeptime, diff, .9, 1.2))
    {
      printf ("dead - after %ju.%.9ju outside reasonable range\n",
	      (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
      result = 1;
    }

  /* Now reap the child and verify that its clock is no longer valid.  */
  {
    int x;
    if (waitpid (child, &x, 0) != child)
      {
	perror ("waitpid");
	result = 1;
      }
  }

  if (clock_gettime (child_clock, &dead) == 0)
    {
      printf ("clock_gettime on reaped PID %d clock %lx => %ju%.9ju\n",
	      child, (unsigned long int) child_clock,
	      (uintmax_t) dead.tv_sec, (uintmax_t) dead.tv_nsec);
      result = 1;
    }
  else
    {
      if (errno != EINVAL)
	result = 1;
      printf ("clock_gettime on reaped PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
    }

  if (clock_getres (child_clock, &dead) == 0)
    {
      printf ("clock_getres on reaped PID %d clock %lx => %ju%.9ju\n",
	      child, (unsigned long int) child_clock,
	      (uintmax_t) dead.tv_sec, (uintmax_t) dead.tv_nsec);
      result = 1;
    }
  else
    {
      if (errno != EINVAL)
	result = 1;
      printf ("clock_getres on reaped PID %d clock %lx => %s\n",
	      child, (unsigned long int) child_clock, strerror (errno));
    }

  return result;

 done:
  {
    if (kill (child, SIGKILL) != 0 && errno != ESRCH)
      {
	perror ("kill");
	return 2;
      }
    int x;
    if (waitpid (child, &x, 0) != child && errno != ECHILD)
      {
	perror ("waitpid");
	return 2;
      }
  }

  return result;
}


#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"