Quelle  hugetlb_fault_after_madv.c   Sprache: C

// SPDX-License-Identifier: GPL-2.0
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <unistd.h>
#include <setjmp.h>
#include <signal.h>

#include "vm_util.h"
#include "../kselftest.h"

#define INLOOP_ITER 100

static char *huge_ptr;
static size_t huge_page_size;

static sigjmp_buf sigbuf;
static bool sigbus_triggered;

static void signal_handler(int signal)
{
 if (signal == SIGBUS) {
  sigbus_triggered = true;
  siglongjmp(sigbuf, 1);
 }
}

/* Touch the memory while it is being madvised() */
void *touch(void *unused)
{
 char *ptr = (char *)huge_ptr;

 if (sigsetjmp(sigbuf, 1))
  return NULL;

 for (int i = 0; i < INLOOP_ITER; i++)
  ptr[0] = '.';

 return NULL;
}

void *madv(void *unused)
{
 usleep(rand() % 10);

 for (int i = 0; i < INLOOP_ITER; i++)
  madvise(huge_ptr, huge_page_size, MADV_DONTNEED);

 return NULL;
}

int main(void)
{
 unsigned long free_hugepages;
 pthread_t thread1, thread2;
 /*
 * On kernel 6.4, we are able to reproduce the problem with ~1000
 * interactions
 */
 int max = 10000;
 int err;

 ksft_print_header();
 ksft_set_plan(1);

 srand(getpid());

 if (signal(SIGBUS, signal_handler) == SIG_ERR)
  ksft_exit_skip("Could not register signal handler.");

 huge_page_size = default_huge_page_size();
 if (!huge_page_size)
  ksft_exit_skip("Could not detect default hugetlb page size.");

 ksft_print_msg("[INFO] detected default hugetlb page size: %zu KiB\n",
         huge_page_size / 1024);

 free_hugepages = get_free_hugepages();
 if (free_hugepages != 1) {
  ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n",
          free_hugepages);
 }

 while (max--) {
  huge_ptr = mmap(NULL, huge_page_size, PROT_READ | PROT_WRITE,
    MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
    -1, 0);

  if ((unsigned long)huge_ptr == -1)
   ksft_exit_skip("Failed to allocated huge page\n");

  pthread_create(&thread1, NULL, madv, NULL);
  pthread_create(&thread2, NULL, touch, NULL);

  pthread_join(thread1, NULL);
  pthread_join(thread2, NULL);
  munmap(huge_ptr, huge_page_size);
 }

 ksft_test_result(!sigbus_triggered, "SIGBUS behavior\n");

 err = ksft_get_fail_cnt();
 if (err)
  ksft_exit_fail_msg("%d out of %d tests failed\n",
       err, ksft_test_num());
 ksft_exit_pass();
}