cascade_flock.c

/*
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 * (the "License").  You may not use this file except
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 *
 * You can obtain a copy of the license at
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/*
 * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*
 * The "cascade" test case is a multiprocess/multithread batten-passing model
 * using lock primitives alone for synchronisation. Threads are arranged in a
 * ring. Each thread has two locks of its own on which it blocks, and is able
 * to manipulate the two locks belonging to the thread which follows it in the
 * ring.
 *
 * The number of threads (nthreads) is specified by the generic libMicro -P/-T
 * options. With nthreads == 1 (the default) the uncontended case can be timed.
 *
 * The main logic is generic and allows any simple blocking API to be tested.
 * The API-specific component is clearly indicated.
 */

#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>

#include "libmicro.h"

#ifndef LOCK_EX
#include "/usr/ucbinclude/sys/file.h"
extern int flock(int fd, int operation);
#endif

typedef struct {
	int			ts_once;
	int			ts_id;
	int			ts_us0;		/* our lock indices */
	int			ts_us1;
	int			ts_them0;	/* their lock indices */
	int			ts_them1;
} tsd_t;

static int			nthreads;

/*
 * API-specific code BEGINS here
 */

#define	DEFD			"/tmp"

static char			*optd = DEFD;
static int			nfiles;
static int			*files;

int
benchmark_init()
{
	lm_tsdsize = sizeof (tsd_t);

	(void) sprintf(lm_optstr, "d:");

	lm_defN = "cscd_flock";

	(void) sprintf(lm_usage,
	    "       [-d directory for temp files (default %s)]\n"
	    "notes: thread cascade using flock file locking\n",
	    DEFD);

	return (0);
}

int
benchmark_optswitch(int opt, char *optarg)
{
	switch (opt) {
	case 'd':
		optd = optarg;
		break;
	default:
		return (-1);
	}
	return (0);
}

int
benchmark_initrun()
{
	int			i;
	int			errors = 0;
	char			fname[1024];

	nthreads = lm_optP * lm_optT;
	nfiles = nthreads * 2;
	(void) setfdlimit(nfiles + 10);
	files = (int *)malloc(nfiles * sizeof (int));
	if (files == NULL) {
		return (1);
	}

	(void) sprintf(fname, "%s/cascade.%ld", optd, getpid());

	for (i = 0; i < nfiles; i++) {
		files[i] = open(fname, O_CREAT | O_TRUNC | O_RDWR, 0600);
		if (files[i] == -1) {
			errors++;
		}
		if (unlink(fname)) {
			errors++;
		}
	}

	return (errors);
}

int
block(int index)
{
	return (flock(files[index], LOCK_EX) == -1);
}

int
unblock(int index)
{
	return (flock(files[index], LOCK_UN) == -1);
}

/*
 * API-specific code ENDS here
 */

int
benchmark_initbatch(void *tsd)
{
	tsd_t			*ts = (tsd_t *)tsd;
	int			e = 0;

	if (ts->ts_once == 0) {
		int		us, them;

		us = (getpindex() * lm_optT) + gettindex();
		them = (us + 1) % (lm_optP * lm_optT);

		ts->ts_id = us;

		/* lock index asignment for us and them */
		ts->ts_us0 = (us * 2);
		ts->ts_us1 = (us * 2) + 1;
		if (us < nthreads - 1) {
			/* straight-thru connection to them */
			ts->ts_them0 = (them * 2);
			ts->ts_them1 = (them * 2) + 1;
		} else {
			/* cross-over connection to them */
			ts->ts_them0 = (them * 2) + 1;
			ts->ts_them1 = (them * 2);
		}

		ts->ts_once = 1;
	}

	/* block their first move */
	e += block(ts->ts_them0);

	return (e);
}

int
benchmark(void *tsd, result_t *res)
{
	tsd_t			*ts = (tsd_t *)tsd;
	int			i;
	int			e = 0;

	/* wait to be unblocked (id == 0 will not block) */
	e += block(ts->ts_us0);

	for (i = 0; i < lm_optB; i += 2) {
		/* allow them to block us again */
		e += unblock(ts->ts_us0);

		/* block their next + 1 move */
		e += block(ts->ts_them1);

		/* unblock their next move */
		e += unblock(ts->ts_them0);

		/* wait for them to unblock us */
		e += block(ts->ts_us1);

		/* repeat with locks reversed */
		e += unblock(ts->ts_us1);
		e += block(ts->ts_them0);
		e += unblock(ts->ts_them1);
		e += block(ts->ts_us0);
	}

	/* finish batch with nothing blocked */
	e += unblock(ts->ts_them0);
	e += unblock(ts->ts_us0);

	res->re_count = i;
	res->re_errors = e;

	return (0);
}