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/* Test rdlock overflow.
Copyright (C) 2000-2023 Free Software Foundation, Inc.
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; see the file COPYING.LIB. If
not, see <https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <error.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#include <pthreadP.h>
#define NREADERS 15
#define READTRIES 5000
#define DELAY 1000000
static pthread_rwlock_t lock = PTHREAD_RWLOCK_INITIALIZER;
static int eagain_returned = 0;
static int success_returned = 0;
static void *
reader_thread (void *nr)
{
struct timespec delay;
int n;
delay.tv_sec = 0;
delay.tv_nsec = DELAY;
for (n = 0; n < READTRIES; ++n)
{
int err = pthread_rwlock_rdlock (&lock);
if (err == EAGAIN)
{
atomic_store_relaxed (&eagain_returned, 1);
continue;
}
else if (err == 0)
atomic_store_relaxed (&success_returned, 1);
else
{
puts ("rdlock failed");
exit (1);
}
nanosleep (&delay, NULL);
if (pthread_rwlock_unlock (&lock) != 0)
{
puts ("unlock for reader failed");
exit (1);
}
}
return NULL;
}
static int
do_test (void)
{
pthread_t thrd[NREADERS];
int n;
void *res;
/* Set the rwlock so that it's close to a reader overflow.
PTHREAD_RWLOCK_WRPHASE and PTHREAD_RWLOCK_WRLOCK are zero initially. */
unsigned int readers = PTHREAD_RWLOCK_READER_OVERFLOW
- ((NREADERS / 3) << PTHREAD_RWLOCK_READER_SHIFT);
lock.__data.__readers = readers;
for (n = 0; n < NREADERS; ++n)
if (pthread_create (&thrd[n], NULL, reader_thread,
(void *) (long int) n) != 0)
{
puts ("reader create failed");
exit (1);
}
/* Wait for all the threads. */
for (n = 0; n < NREADERS; ++n)
if (pthread_join (thrd[n], &res) != 0)
{
puts ("reader join failed");
exit (1);
}
if (atomic_load_relaxed (&eagain_returned) == 0)
{
puts ("EAGAIN has never been returned");
exit (1);
}
if (atomic_load_relaxed (&success_returned) == 0)
{
puts ("rdlock was never successfully acquired");
exit (1);
}
if (lock.__data.__readers != readers)
{
puts ("__readers in rwlock differs from initial value");
exit (1);
}
return 0;
}
#define TIMEOUT 100
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"
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