/* Test rwlock with PREFER_WRITER_NONRECURSIVE_NP (bug 23861).

   Copyright (C) 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/>.  */

#include <stdio.h>

#include <stdlib.h>

#include <unistd.h>

#include <pthread.h>

#include <support/xthread.h>

/* We choose 10 iterations because this happens to be able to trigger the

   stall on contemporary hardware.  */

#define LOOPS 10

/* We need 3 threads to trigger bug 23861.  One thread as a writer, and

   two reader threads.  The test verifies that the second-to-last reader

   is able to notify the *last* reader that it should be done waiting.

   If the second-to-last reader fails to notify the last reader or does

   so incorrectly then the last reader may stall indefinitely.  */

#define NTHREADS 3

_Atomic int do_exit;

pthread_rwlockattr_t mylock_attr;

pthread_rwlock_t mylock;

void *

run_loop (void *a)

{

  while (!do_exit)

    {

      if (random () & 1)

	{

	  xpthread_rwlock_wrlock (&mylock);

	  xpthread_rwlock_unlock (&mylock);

	}

      else

	{

	  xpthread_rwlock_rdlock (&mylock);

	  xpthread_rwlock_unlock (&mylock);

	}

    }

  return NULL;

}

int

do_test (void)

{

  xpthread_rwlockattr_init (&mylock_attr);

  xpthread_rwlockattr_setkind_np (&mylock_attr,

				  PTHREAD_RWLOCK_PREFER_WRITER_NONRECURSIVE_NP);

  xpthread_rwlock_init (&mylock, &mylock_attr);

  for (int n = 0; n < LOOPS; n++)

    {

      pthread_t tids[NTHREADS];

      do_exit = 0;

      for (int i = 0; i < NTHREADS; i++)

	tids[i] = xpthread_create (NULL, run_loop, NULL);

      /* Let the threads run for some time.  */

      sleep (1);

      printf ("Exiting...");

      fflush (stdout);

      do_exit = 1;

      for (int i = 0; i < NTHREADS; i++)

	xpthread_join (tids[i]);

      printf ("done.\n");

    }

  pthread_rwlock_destroy (&mylock);

  pthread_rwlockattr_destroy (&mylock_attr);

  return 0;

}

#define TIMEOUT (DEFAULT_TIMEOUT + 3 * LOOPS)

#include <support/test-driver.c>