127 lines
2.8 KiB
C
127 lines
2.8 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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/*
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* A test case that must run on a system with one and only one huge page available.
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* # echo 1 > /sys/kernel/mm/hugepages/hugepages-2048kB/nr_hugepages
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*
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* During setup, the test allocates the only available page, and starts three threads:
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* - thread1:
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* * madvise(MADV_DONTNEED) on the allocated huge page
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* - thread 2:
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* * Write to the allocated huge page
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* - thread 3:
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* * Try to allocated an extra huge page (which must not available)
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*
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* The test fails if thread3 is able to allocate a page.
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*
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* Touching the first page after thread3's allocation will raise a SIGBUS
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*
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* Author: Breno Leitao <leitao@debian.org>
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*/
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#include <pthread.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include "vm_util.h"
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#include "../kselftest.h"
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#define INLOOP_ITER 100
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size_t mmap_size;
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char *huge_ptr;
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/* Touch the memory while it is being madvised() */
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void *touch(void *unused)
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{
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for (int i = 0; i < INLOOP_ITER; i++)
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huge_ptr[0] = '.';
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return NULL;
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}
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void *madv(void *unused)
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{
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for (int i = 0; i < INLOOP_ITER; i++)
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madvise(huge_ptr, mmap_size, MADV_DONTNEED);
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return NULL;
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}
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/*
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* We got here, and there must be no huge page available for mapping
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* The other hugepage should be flipping from used <-> reserved, because
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* of madvise(DONTNEED).
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*/
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void *map_extra(void *unused)
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{
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void *ptr;
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for (int i = 0; i < INLOOP_ITER; i++) {
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ptr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
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-1, 0);
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if ((long)ptr != -1) {
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/* Touching the other page now will cause a SIGBUG
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* huge_ptr[0] = '1';
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*/
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return ptr;
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}
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}
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return NULL;
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}
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int main(void)
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{
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pthread_t thread1, thread2, thread3;
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unsigned long free_hugepages;
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void *ret;
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/*
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* On kernel 6.7, we are able to reproduce the problem with ~10
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* interactions
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*/
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int max = 10;
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free_hugepages = get_free_hugepages();
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if (free_hugepages != 1) {
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ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n",
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free_hugepages);
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}
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mmap_size = default_huge_page_size();
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while (max--) {
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huge_ptr = mmap(NULL, mmap_size, PROT_READ | PROT_WRITE,
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MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB,
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-1, 0);
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if ((unsigned long)huge_ptr == -1) {
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ksft_test_result_fail("Failed to allocate huge page\n");
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return KSFT_FAIL;
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}
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pthread_create(&thread1, NULL, madv, NULL);
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pthread_create(&thread2, NULL, touch, NULL);
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pthread_create(&thread3, NULL, map_extra, NULL);
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pthread_join(thread1, NULL);
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pthread_join(thread2, NULL);
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pthread_join(thread3, &ret);
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if (ret) {
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ksft_test_result_fail("Unexpected huge page allocation\n");
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return KSFT_FAIL;
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}
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/* Unmap and restart */
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munmap(huge_ptr, mmap_size);
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}
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return KSFT_PASS;
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}
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