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116d57303a
Create a selftest that exercises the race between page faults and madvise(MADV_DONTNEED) in the same huge page. Do it by running two threads that touches the huge page and madvise(MADV_DONTNEED) at the same time. In case of a SIGBUS coming at pagefault, the test should fail, since we hit the bug. The test doesn't have a signal handler, and if it fails, it fails like the following ---------------------------------- running ./hugetlb_fault_after_madv ---------------------------------- ./run_vmtests.sh: line 186: 595563 Bus error (core dumped) "$@" [FAIL] This selftest goes together with the fix of the bug[1] itself. [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r Link: https://lkml.kernel.org/r/20231005163922.87568-3-leitao@debian.org Signed-off-by: Breno Leitao <leitao@debian.org> Reviewed-by: Rik van Riel <riel@surriel.com> Tested-by: Rik van Riel <riel@surriel.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Muchun Song <muchun.song@linux.dev> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
74 lines
1.4 KiB
C
74 lines
1.4 KiB
C
// SPDX-License-Identifier: GPL-2.0
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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 MMAP_SIZE (1 << 21)
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#define INLOOP_ITER 100
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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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char *ptr = (char *)huge_ptr;
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for (int i = 0; i < INLOOP_ITER; i++)
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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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usleep(rand() % 10);
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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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int main(void)
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{
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unsigned long free_hugepages;
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pthread_t thread1, thread2;
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/*
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* On kernel 6.4, we are able to reproduce the problem with ~1000
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* interactions
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*/
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int max = 10000;
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srand(getpid());
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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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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_exit_skip("Failed to allocated huge page\n");
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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_join(thread1, NULL);
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pthread_join(thread2, NULL);
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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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