1// SPDX-License-Identifier: GPL-2.0
2#include <pthread.h>
3#include <stdio.h>
4#include <stdlib.h>
5#include <sys/mman.h>
6#include <sys/types.h>
7#include <unistd.h>
8
9#include "vm_util.h"
10#include "../kselftest.h"
11
12#define MMAP_SIZE (1 << 21)
13#define INLOOP_ITER 100
14
15char *huge_ptr;
16
17/* Touch the memory while it is being madvised() */
18void *touch(void *unused)
19{
20 char *ptr = (char *)huge_ptr;
21
22 for (int i = 0; i < INLOOP_ITER; i++)
23 ptr[0] = '.';
24
25 return NULL;
26}
27
28void *madv(void *unused)
29{
30 usleep(rand() % 10);
31
32 for (int i = 0; i < INLOOP_ITER; i++)
33 madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED);
34
35 return NULL;
36}
37
38int main(void)
39{
40 unsigned long free_hugepages;
41 pthread_t thread1, thread2;
42 /*
43 * On kernel 6.4, we are able to reproduce the problem with ~1000
44 * interactions
45 */
46 int max = 10000;
47
48 srand(getpid());
49
50 free_hugepages = get_free_hugepages();
51 if (free_hugepages != 1) {
52 ksft_exit_skip(msg: "This test needs one and only one page to execute. Got %lu\n",
53 free_hugepages);
54 }
55
56 while (max--) {
57 huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,
58 MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
59 -1, 0);
60
61 if ((unsigned long)huge_ptr == -1)
62 ksft_exit_skip(msg: "Failed to allocated huge page\n");
63
64 pthread_create(&thread1, NULL, madv, NULL);
65 pthread_create(&thread2, NULL, touch, NULL);
66
67 pthread_join(thread1, NULL);
68 pthread_join(thread2, NULL);
69 munmap(huge_ptr, MMAP_SIZE);
70 }
71
72 return KSFT_PASS;
73}
74

source code of linux/tools/testing/selftests/mm/hugetlb_fault_after_madv.c