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/* Test rwlocks.
Copyright (C) 2000-2024 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
<https://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;
}
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