futex.c

 1// SPDX-License-Identifier: GPL-2.0
 2#include <err.h>
 3#include <errno.h>
 4#include <stdio.h>
 5#include <stdlib.h>
 6#include <sys/prctl.h>
 7
 8#include "futex.h"
 9
10#ifndef PR_FUTEX_HASH
11#define PR_FUTEX_HASH                   78
12# define PR_FUTEX_HASH_SET_SLOTS        1
13# define PR_FUTEX_HASH_GET_SLOTS        2
14#endif // PR_FUTEX_HASH
15
16void futex_set_nbuckets_param(struct bench_futex_parameters *params)
17{
18	int ret;
19
20	if (params->nbuckets < 0)
21		return;
22
23	ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, params->nbuckets, 0);
24	if (ret) {
25		printf("Requesting %d hash buckets failed: %d/%m\n",
26		       params->nbuckets, ret);
27		err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
28	}
29}
30
31void futex_print_nbuckets(struct bench_futex_parameters *params)
32{
33	char *futex_hash_mode;
34	int ret;
35
36	ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_GET_SLOTS);
37	if (params->nbuckets >= 0) {
38		if (ret != params->nbuckets) {
39			if (ret < 0) {
40				printf("Can't query number of buckets: %m\n");
41				err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
42			}
43			printf("Requested number of hash buckets does not currently used.\n");
44			printf("Requested: %d in usage: %d\n", params->nbuckets, ret);
45			err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
46		}
47		if (params->nbuckets == 0)
48			ret = asprintf(&futex_hash_mode, "Futex hashing: global hash");
49		else
50			ret = asprintf(&futex_hash_mode, "Futex hashing: %d hash buckets",
51				       params->nbuckets);
52	} else {
53		if (ret <= 0) {
54			ret = asprintf(&futex_hash_mode, "Futex hashing: global hash");
55		} else {
56			ret = asprintf(&futex_hash_mode, "Futex hashing: auto resized to %d buckets",
57				       ret);
58		}
59	}
60	if (ret < 0)
61		err(EXIT_FAILURE, "ENOMEM, futex_hash_mode");
62	printf("%s\n", futex_hash_mode);
63	free(futex_hash_mode);
64}