hugetlb_fault_after_madv.c

  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#include <setjmp.h>
  9#include <signal.h>
 10
 11#include "vm_util.h"
 12#include "kselftest.h"
 13
 14#define INLOOP_ITER 100
 15
 16static char *huge_ptr;
 17static size_t huge_page_size;
 18
 19static sigjmp_buf sigbuf;
 20static bool sigbus_triggered;
 21
 22static void signal_handler(int signal)
 23{
 24	if (signal == SIGBUS) {
 25		sigbus_triggered = true;
 26		siglongjmp(sigbuf, 1);
 27	}
 28}
 29
 30/* Touch the memory while it is being madvised() */
 31void *touch(void *unused)
 32{
 33	char *ptr = (char *)huge_ptr;
 34
 35	if (sigsetjmp(sigbuf, 1))
 36		return NULL;
 37
 38	for (int i = 0; i < INLOOP_ITER; i++)
 39		ptr[0] = '.';
 40
 41	return NULL;
 42}
 43
 44void *madv(void *unused)
 45{
 46	usleep(rand() % 10);
 47
 48	for (int i = 0; i < INLOOP_ITER; i++)
 49		madvise(huge_ptr, huge_page_size, MADV_DONTNEED);
 50
 51	return NULL;
 52}
 53
 54int main(void)
 55{
 56	unsigned long free_hugepages;
 57	pthread_t thread1, thread2;
 58	/*
 59	 * On kernel 6.4, we are able to reproduce the problem with ~1000
 60	 * interactions
 61	 */
 62	int max = 10000;
 63	int err;
 64
 65	ksft_print_header();
 66	ksft_set_plan(1);
 67
 68	srand(getpid());
 69
 70	if (signal(SIGBUS, signal_handler) == SIG_ERR)
 71		ksft_exit_skip("Could not register signal handler.");
 72
 73	huge_page_size = default_huge_page_size();
 74	if (!huge_page_size)
 75		ksft_exit_skip("Could not detect default hugetlb page size.");
 76
 77	ksft_print_msg("[INFO] detected default hugetlb page size: %zu KiB\n",
 78		       huge_page_size / 1024);
 79
 80	free_hugepages = get_free_hugepages();
 81	if (free_hugepages != 1) {
 82		ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n",
 83			       free_hugepages);
 84	}
 85
 86	while (max--) {
 87		huge_ptr = mmap(NULL, huge_page_size, PROT_READ | PROT_WRITE,
 88				MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
 89				-1, 0);
 90
 91		if ((unsigned long)huge_ptr == -1)
 92			ksft_exit_skip("Failed to allocated huge page\n");
 93
 94		pthread_create(&thread1, NULL, madv, NULL);
 95		pthread_create(&thread2, NULL, touch, NULL);
 96
 97		pthread_join(thread1, NULL);
 98		pthread_join(thread2, NULL);
 99		munmap(huge_ptr, huge_page_size);
100	}
101
102	ksft_test_result(!sigbus_triggered, "SIGBUS behavior\n");
103
104	err = ksft_get_fail_cnt();
105	if (err)
106		ksft_exit_fail_msg("%d out of %d tests failed\n",
107				   err, ksft_test_num());
108	ksft_exit_pass();
109}