Quelle  futex.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/prctl.h>

#include "futex.h"

#ifndef PR_FUTEX_HASH
#define PR_FUTEX_HASH                   78
# define PR_FUTEX_HASH_SET_SLOTS        1
# define PR_FUTEX_HASH_GET_SLOTS        2
#endif // PR_FUTEX_HASH

void futex_set_nbuckets_param(struct bench_futex_parameters *params)
{
 int ret;

 if (params->nbuckets < 0)
  return;

 ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_SET_SLOTS, params->nbuckets, 0);
 if (ret) {
  printf("Requesting %d hash buckets failed: %d/%m\n",
         params->nbuckets, ret);
  err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
 }
}

void futex_print_nbuckets(struct bench_futex_parameters *params)
{
 char *futex_hash_mode;
 int ret;

 ret = prctl(PR_FUTEX_HASH, PR_FUTEX_HASH_GET_SLOTS);
 if (params->nbuckets >= 0) {
  if (ret != params->nbuckets) {
   if (ret < 0) {
    printf("Can't query number of buckets: %m\n");
    err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
   }
   printf("Requested number of hash buckets does not currently used.\n");
   printf("Requested: %d in usage: %d\n", params->nbuckets, ret);
   err(EXIT_FAILURE, "prctl(PR_FUTEX_HASH)");
  }
  if (params->nbuckets == 0)
   ret = asprintf(&futex_hash_mode, "Futex hashing: global hash");
  else
   ret = asprintf(&futex_hash_mode, "Futex hashing: %d hash buckets",
           params->nbuckets);
 } else {
  if (ret <= 0) {
   ret = asprintf(&futex_hash_mode, "Futex hashing: global hash");
  } else {
   ret = asprintf(&futex_hash_mode, "Futex hashing: auto resized to %d buckets",
           ret);
  }
 }
 if (ret < 0)
  err(EXIT_FAILURE, "ENOMEM, futex_hash_mode");
 printf("%s\n", futex_hash_mode);
 free(futex_hash_mode);
}