/* Test rwlocks.

   Copyright (C) 2000-2018 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

   <http://www.gnu.org/licenses/>.  */

#define _GNU_SOURCE

#include <pthread.h>

#include <assert.h>

#include <error.h>

#include <errno.h>

#define THREADS 1

int a;

int b;

/* Get a read lock and assert that a == b.  */

void *

test1 (void *arg)

{

  error_t err;

  pthread_rwlock_t *lock = arg;

  int i;

  for (i = 0; i < 200; i++)

    {

      err = pthread_rwlock_rdlock (lock);

      assert (err == 0);

      assert (a == b);

      sched_yield ();

      assert (a == b);

      err = pthread_rwlock_unlock (lock);

      assert (err == 0);

    }

  return 0;

}

int

main (int argc, char **argv)

{

  error_t err;

  pthread_rwlockattr_t attr;

  pthread_rwlock_t lock;

  int pshared;

  int i;

  pthread_t tid[THREADS];

  void *ret;

  err = pthread_rwlockattr_init (&attr);

  if (err)

    error (1, err, "pthread_rwlockattr_init");

  err = pthread_rwlockattr_getpshared (&attr, &pshared);

  if (err)

    error (1, err, "pthread_rwlockattr_getpshared");

  /* Assert the default state as mandated by POSIX.  */

  assert (pshared == PTHREAD_PROCESS_PRIVATE);

  err = pthread_rwlockattr_setpshared (&attr, pshared);

  if (err)

    error (1, err, "pthread_rwlockattr_setpshared");

  err = pthread_rwlock_init (&lock, &attr);

  if (err)

    error (1, err, "pthread_rwlock_init");

  err = pthread_rwlockattr_destroy (&attr);

  if (err)

    error (1, err, "pthread_rwlockattr_destroy");

  /* Now test the lock.  */

  for (i = 0; i < THREADS; i++)

    {

      err = pthread_create (&tid[i], 0, test1, &lock);

      if (err)

	error (1, err, "pthread_create");

    }

  for (i = 0; i < 10; i++)

    {

      sched_yield ();

      /* Get a write lock.  */

      pthread_rwlock_wrlock (&lock);

      /* Increment a and b giving other threads a chance to run in

         between.  */

      sched_yield ();

      a++;

      sched_yield ();

      b++;

      sched_yield ();

      /* Unlock.  */

      pthread_rwlock_unlock (&lock);

    }

  for (i = 0; i < THREADS; i++)

    {

      err = pthread_join (tid[i], &ret;;

      if (err)

	error (1, err, "pthread_join");

    }

  /* Read lock it.  */

  err = pthread_rwlock_tryrdlock (&lock);

  assert (err == 0);

  /* Try to write lock it.  It should fail with EBUSY.  */

  err = pthread_rwlock_trywrlock (&lock);

  assert (err == EBUSY);

  /* Drop the read lock.  */

  err = pthread_rwlock_unlock (&lock);

  assert (err == 0);

  /* Get a write lock.  */

  err = pthread_rwlock_trywrlock (&lock);

  assert (err == 0);

  /* Fail trying to acquire another write lock.  */

  err = pthread_rwlock_trywrlock (&lock);

  assert (err == EBUSY);

  /* Try to get a read lock which should also fail.  */

  err = pthread_rwlock_tryrdlock (&lock);

  assert (err == EBUSY);

  /* Unlock it.  */

  err = pthread_rwlock_unlock (&lock);

  assert (err == 0);

  err = pthread_rwlock_destroy (&lock);

  if (err)

    error (1, err, "pthread_rwlock_destroy");

  return 0;

}