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/* Test of read-write locks in multithreaded situations.
Copyright (C) 2005, 2008-2023 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Bruno Haible <bruno@clisp.org>, 2005. */
#include <config.h>
#if USE_ISOC_THREADS || USE_POSIX_THREADS || USE_ISOC_AND_POSIX_THREADS || USE_WINDOWS_THREADS
/* Whether to enable locking.
Uncomment this to get a test program without locking, to verify that
it crashes. */
#define ENABLE_LOCKING 1
/* Whether to help the scheduler through explicit sched_yield().
Uncomment this to see if the operating system has a fair scheduler. */
#define EXPLICIT_YIELD 1
/* Whether to print debugging messages. */
#define ENABLE_DEBUGGING 0
/* Number of simultaneous threads. */
#define THREAD_COUNT 10
/* Number of operations performed in each thread.
This is quite high, because with a smaller count, say 5000, we often get
an "OK" result even without ENABLE_LOCKING (on Linux/x86). */
#define REPEAT_COUNT 50000
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#if EXPLICIT_YIELD
# include <sched.h>
#endif
#if HAVE_DECL_ALARM
# include <signal.h>
# include <unistd.h>
#endif
#include "macros.h"
#include "atomic-int-posix.h"
#if ENABLE_DEBUGGING
# define dbgprintf printf
#else
# define dbgprintf if (0) printf
#endif
#if EXPLICIT_YIELD
# define yield() sched_yield ()
#else
# define yield()
#endif
/* Returns a reference to the current thread as a pointer, for debugging. */
#if defined __MVS__
/* On IBM z/OS, pthread_t is a struct with an 8-byte '__' field.
The first three bytes of this field appear to uniquely identify a
pthread_t, though not necessarily representing a pointer. */
# define pthread_self_pointer() (*((void **) pthread_self ().__))
#else
# define pthread_self_pointer() ((void *) (uintptr_t) pthread_self ())
#endif
#define ACCOUNT_COUNT 4
static int account[ACCOUNT_COUNT];
static int
random_account (void)
{
return ((unsigned int) rand () >> 3) % ACCOUNT_COUNT;
}
static void
check_accounts (void)
{
int i, sum;
sum = 0;
for (i = 0; i < ACCOUNT_COUNT; i++)
sum += account[i];
if (sum != ACCOUNT_COUNT * 1000)
abort ();
}
/* ----------------- Test read-write (non-recursive) locks ----------------- */
/* Test read-write locks by having several bank accounts and several threads
which shuffle around money between the accounts and several other threads
that check that all the money is still there. */
static pthread_rwlock_t my_rwlock = PTHREAD_RWLOCK_INITIALIZER;
static void *
rwlock_mutator_thread (void *arg)
{
int repeat;
for (repeat = REPEAT_COUNT; repeat > 0; repeat--)
{
int i1, i2, value;
dbgprintf ("Mutator %p before wrlock\n", pthread_self_pointer ());
ASSERT (pthread_rwlock_wrlock (&my_rwlock) == 0);
dbgprintf ("Mutator %p after wrlock\n", pthread_self_pointer ());
i1 = random_account ();
i2 = random_account ();
value = ((unsigned int) rand () >> 3) % 10;
account[i1] += value;
account[i2] -= value;
dbgprintf ("Mutator %p before unlock\n", pthread_self_pointer ());
ASSERT (pthread_rwlock_unlock (&my_rwlock) == 0);
dbgprintf ("Mutator %p after unlock\n", pthread_self_pointer ());
yield ();
}
dbgprintf ("Mutator %p dying.\n", pthread_self_pointer ());
return NULL;
}
static struct atomic_int rwlock_checker_done;
static void *
rwlock_checker_thread (void *arg)
{
while (get_atomic_int_value (&rwlock_checker_done) == 0)
{
dbgprintf ("Checker %p before check rdlock\n", pthread_self_pointer ());
ASSERT (pthread_rwlock_rdlock (&my_rwlock) == 0);
check_accounts ();
ASSERT (pthread_rwlock_unlock (&my_rwlock) == 0);
dbgprintf ("Checker %p after check unlock\n", pthread_self_pointer ());
yield ();
}
dbgprintf ("Checker %p dying.\n", pthread_self_pointer ());
return NULL;
}
static void
test_rwlock (void)
{
int i;
pthread_t checkerthreads[THREAD_COUNT];
pthread_t threads[THREAD_COUNT];
/* Initialization. */
for (i = 0; i < ACCOUNT_COUNT; i++)
account[i] = 1000;
init_atomic_int (&rwlock_checker_done);
set_atomic_int_value (&rwlock_checker_done, 0);
/* Spawn the threads. */
for (i = 0; i < THREAD_COUNT; i++)
ASSERT (pthread_create (&checkerthreads[i], NULL,
rwlock_checker_thread, NULL)
== 0);
for (i = 0; i < THREAD_COUNT; i++)
ASSERT (pthread_create (&threads[i], NULL, rwlock_mutator_thread, NULL)
== 0);
/* Wait for the threads to terminate. */
for (i = 0; i < THREAD_COUNT; i++)
ASSERT (pthread_join (threads[i], NULL) == 0);
set_atomic_int_value (&rwlock_checker_done, 1);
for (i = 0; i < THREAD_COUNT; i++)
ASSERT (pthread_join (checkerthreads[i], NULL) == 0);
check_accounts ();
}
/* -------------------------------------------------------------------------- */
int
main ()
{
#if HAVE_DECL_ALARM
/* Declare failure if test takes too long, by using default abort
caused by SIGALRM. */
int alarm_value = 600;
signal (SIGALRM, SIG_DFL);
alarm (alarm_value);
#endif
printf ("Starting test_rwlock ..."); fflush (stdout);
test_rwlock ();
printf (" OK\n"); fflush (stdout);
return 0;
}
#else
/* No multithreading available. */
#include <stdio.h>
int
main ()
{
fputs ("Skipping test: multithreading not enabled\n", stderr);
return 77;
}
#endif
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