x15/test/test_sref_dirty_zeroes.c

/*
 * Copyright (c) 2014-2019 Richard Braun.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *
 * The purpose of this test module is to produce dirty zeroes and make
 * sure they're correctly processed. It is a stress test that never ends,
 * except on failure. Two threads are created. The first increments a
 * scalable reference counter, then signals the second that it can decrement
 * it. Since these threads are likely to run on different processors, a
 * good amount of dirty zeroes should be produced, as reported by regularly
 * printing the relevant event counters. Since the true number of references
 * can never drop to 0, the no-reference function should never be called,
 * and panics if it is.
 */

#include <stddef.h>
#include <stdio.h>

#include <kern/condition.h>
#include <kern/init.h>
#include <kern/kmem.h>
#include <kern/log.h>
#include <kern/macros.h>
#include <kern/mutex.h>
#include <kern/panic.h>
#include <kern/sref.h>
#include <kern/syscnt.h>
#include <kern/thread.h>

#include <test/test.h>

#include <vm/kmem.h>

static struct condition test_condition;
static struct mutex test_lock;
static struct sref_counter test_counter;
static unsigned long test_transient_ref;

static void
test_inc (void *arg __unused)
{
  while (1)
    {
      for (volatile unsigned long i = 0; i < 1000000; i++)
        {
          sref_counter_inc (&test_counter);

          mutex_lock (&test_lock);
          test_transient_ref++;
          condition_signal (&test_condition);

          while (test_transient_ref)
            condition_wait (&test_condition, &test_lock);

          mutex_unlock (&test_lock);
        }

      printf ("counter global value: %lu\n", test_counter.value);
      syscnt_info ("sref_epoch", log_stream_info ());
      syscnt_info ("sref_dirty_zero", log_stream_info ());
      syscnt_info ("sref_true_zero", log_stream_info ());
    }
}

static void
test_dec (void *arg __unused)
{
  while (1)
    {
      mutex_lock (&test_lock);

      while (! test_transient_ref)
        condition_wait (&test_condition, &test_lock);

      --test_transient_ref;
      condition_signal (&test_condition);
      mutex_unlock (&test_lock);

      sref_counter_dec (&test_counter);
    }
}

static void
test_noref (struct sref_counter *counter __unused)
{
  panic ("0 references, page released\n");
}

TEST_INLINE (sref_dirty_zeroes)
{
  condition_init (&test_condition);
  mutex_init (&test_lock);

  sref_counter_init (&test_counter, 1, NULL, test_noref);
  test_transient_ref = 0;

  struct thread_attr attr;
  thread_attr_init (&attr, THREAD_KERNEL_PREFIX "test_inc");
  thread_attr_set_detached (&attr);
  int error = thread_create (NULL, &attr, test_inc, NULL);
  test_assert_zero (error);

  thread_attr_init (&attr, THREAD_KERNEL_PREFIX "test_dec");
  thread_attr_set_detached (&attr);
  error = thread_create (NULL, &attr, test_dec, NULL);
  test_assert_zero (error);

  return (TEST_RUNNING);
}