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("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("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