/* Copyright (C) 2015-2018 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/>.  */

/* This tests that a writer that is preferred -- but times out due to a

   reader being present -- does not miss to wake other readers blocked on the

   writer's pending lock acquisition.  */

#include <errno.h>

#include <pthread.h>

#include <stdio.h>

#include <stdlib.h>

#include <time.h>

/* The bug existed in the code that strictly prefers writers over readers.  */

static pthread_rwlock_t r = PTHREAD_RWLOCK_WRITER_NONRECURSIVE_INITIALIZER_NP;

static void *

writer (void *arg)

{

  struct timespec ts;

  if (clock_gettime (CLOCK_REALTIME, &ts) != 0)

    {

      puts ("clock_gettime failed");

      exit (EXIT_FAILURE);

    }

  ts.tv_sec += 1;

  int e = pthread_rwlock_timedwrlock (&r, &ts);

  if (e != ETIMEDOUT)

    {

      puts ("timedwrlock did not time out");

      exit (EXIT_FAILURE);

    }

  return NULL;

}

static void *

reader (void *arg)

{

  /* This isn't a reliable way to get the interleaving we need (because a

     failed trylock doesn't synchronize with the writer, and because we could

     try to lock after the writer has already timed out).  However, both will

     just lead to false positives.  */

  int e;

  while ((e = pthread_rwlock_tryrdlock (&r)) != EBUSY)

    {

      if (e != 0)

	exit (EXIT_FAILURE);

      pthread_rwlock_unlock (&r);

    }

  e = pthread_rwlock_rdlock (&r);

  if (e != 0)

    {

      puts ("reader rdlock failed");

      exit (EXIT_FAILURE);

    }

  pthread_rwlock_unlock (&r);

  return NULL;

}

static int

do_test (void)

{

  /* Grab a rdlock, then create a writer and a reader, and wait until they

     finished.  */

  if (pthread_rwlock_rdlock (&r) != 0)

    {

      puts ("initial rdlock failed");

      return 1;

    }

  pthread_t thw;

  if (pthread_create (&thw, NULL, writer, NULL) != 0)

    {

      puts ("create failed");

      return 1;

    }

  pthread_t thr;

  if (pthread_create (&thr, NULL, reader, NULL) != 0)

    {

      puts ("create failed");

      return 1;

    }

  if (pthread_join (thw, NULL) != 0)

    {

      puts ("writer join failed");

      return 1;

    }

  if (pthread_join (thr, NULL) != 0)

    {

      puts ("reader join failed");

      return 1;

    }

  return 0;

}

#define TEST_FUNCTION do_test ()

#include "../test-skeleton.c"