membar_test.c

/* $Id: membar_test.c,v 1.4 2021/10/08 12:33:32 kostik Exp kostik $ */

#include <sys/types.h>
#ifndef OLDSYSTEM
#include <sys/membarrier.h>
#endif
#include <err.h>
#include <errno.h>
#include <pthread.h>
#include <stdatomic.h>
#include <stdbool.h>
#include <stdio.h>
#include <unistd.h>

#ifdef OLDSYSTEM
#define	MEMBARRIER_CMD_QUERY				0x00000000
#define	MEMBARRIER_CMD_GLOBAL				0x00000001
#define	MEMBARRIER_CMD_GLOBAL_EXPEDITED			0x00000002
#define	MEMBARRIER_CMD_REGISTER_GLOBAL_EXPEDITED	0x00000004
#define	MEMBARRIER_CMD_PRIVATE_EXPEDITED		0x00000008
#define	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED	0x00000010
#define	MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE	0x00000020
#define	MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE	0x00000040
int membarrier(int, unsigned, int);
int
membarrier(int cmd __unused, unsigned flags __unused, int cpu_id __unused)
{
	errno = ENOSYS;
	return (-1);
}
#endif

static const int nrepeats = 1000000;

static void *
test_private_expedited_thr_func(void *arg)
{
	atomic_int *done;

	done = arg;
	while (atomic_load_explicit(done, memory_order_relaxed) == 0)
		;
	return (NULL);
}

static void
test_private_expedited(const char *title, int cmd_reg, int cmd)
{
	int error, ncpus, i;
	atomic_int done;

	ncpus = sysconf(_SC_NPROCESSORS_ONLN);
	if (ncpus == -1)
		err(1, "ncpus");

	error = membarrier(cmd_reg, 0, 0);
	if (error == -1)
		err(1, "register priv expedited");

	int nthreads = ncpus * 2;
	printf("starting %s on %d cpus (%d threads), %d calls\n",
	    title, ncpus, nthreads, nrepeats);

	pthread_t thrs[nthreads];
	atomic_store_explicit(&done, 0, memory_order_relaxed);
	for (i = 0; i < nthreads; i++) {
		error = pthread_create(&thrs[i], NULL,
		    test_private_expedited_thr_func, &done);
		if (error != 0)
			errc(1, error, "pthread_create");
	}
	for (i = 0; i < nrepeats; i++)
		membarrier(cmd, 0, 0);
	atomic_store_explicit(&done, 1, memory_order_relaxed);
	for (i = 0; i < nthreads; i++) {
		error = pthread_join(thrs[i], NULL);
		if (error != 0)
			errc(1, error, "pthread_join");
	}
}

int
main(void)
{
	int res;

	res = membarrier(MEMBARRIER_CMD_QUERY, 0, 0);
	if (res == -1)
		err(1, "query");
	printf("supported commands %#x\n", res);

	if ((res & MEMBARRIER_CMD_PRIVATE_EXPEDITED) != 0)
		test_private_expedited("private expedited",
		    MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED,
		    MEMBARRIER_CMD_PRIVATE_EXPEDITED);
	if ((res & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) != 0)
		test_private_expedited("private expedited core sync",
		    MEMBARRIER_CMD_REGISTER_PRIVATE_EXPEDITED_SYNC_CORE,
		    MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE);
}