From 116d57303a051bb2c7939a5026e441d8a7845db2 Mon Sep 17 00:00:00 2001 From: Breno Leitao Date: Thu, 5 Oct 2023 09:39:22 -0700 Subject: [PATCH] selftests/mm: add a new test for madv and hugetlb 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) "$@" [FAIL] This selftest goes together with the fix of the bug[1] itself. [1] https://lore.kernel.org/all/20231001005659.2185316-1-riel@surriel.com/#r Link: https://lkml.kernel.org/r/20231005163922.87568-3-leitao@debian.org Signed-off-by: Breno Leitao Reviewed-by: Rik van Riel Tested-by: Rik van Riel Cc: Mike Kravetz Cc: Muchun Song Signed-off-by: Andrew Morton --- tools/testing/selftests/mm/Makefile | 1 + .../selftests/mm/hugetlb_fault_after_madv.c | 73 +++++++++++++++++++ tools/testing/selftests/mm/run_vmtests.sh | 4 + 3 files changed, 78 insertions(+) create mode 100644 tools/testing/selftests/mm/hugetlb_fault_after_madv.c diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile index 2a89989afafc..78dfec8bc676 100644 --- a/tools/testing/selftests/mm/Makefile +++ b/tools/testing/selftests/mm/Makefile @@ -69,6 +69,7 @@ TEST_GEN_FILES += split_huge_page_test TEST_GEN_FILES += ksm_tests TEST_GEN_FILES += ksm_functional_tests TEST_GEN_FILES += mdwe_test +TEST_GEN_FILES += hugetlb_fault_after_madv ifneq ($(ARCH),arm64) TEST_GEN_PROGS += soft-dirty diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c new file mode 100644 index 000000000000..73b81c632366 --- /dev/null +++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include + +#include "vm_util.h" +#include "../kselftest.h" + +#define MMAP_SIZE (1 << 21) +#define INLOOP_ITER 100 + +char *huge_ptr; + +/* Touch the memory while it is being madvised() */ +void *touch(void *unused) +{ + char *ptr = (char *)huge_ptr; + + for (int i = 0; i < INLOOP_ITER; i++) + ptr[0] = '.'; + + return NULL; +} + +void *madv(void *unused) +{ + usleep(rand() % 10); + + for (int i = 0; i < INLOOP_ITER; i++) + madvise(huge_ptr, MMAP_SIZE, MADV_DONTNEED); + + return NULL; +} + +int main(void) +{ + unsigned long free_hugepages; + pthread_t thread1, thread2; + /* + * On kernel 6.4, we are able to reproduce the problem with ~1000 + * interactions + */ + int max = 10000; + + srand(getpid()); + + free_hugepages = get_free_hugepages(); + if (free_hugepages != 1) { + ksft_exit_skip("This test needs one and only one page to execute. Got %lu\n", + free_hugepages); + } + + while (max--) { + huge_ptr = mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB, + -1, 0); + + if ((unsigned long)huge_ptr == -1) + ksft_exit_skip("Failed to allocated huge page\n"); + + pthread_create(&thread1, NULL, madv, NULL); + pthread_create(&thread2, NULL, touch, NULL); + + pthread_join(thread1, NULL); + pthread_join(thread2, NULL); + munmap(huge_ptr, MMAP_SIZE); + } + + return KSFT_PASS; +} diff --git a/tools/testing/selftests/mm/run_vmtests.sh b/tools/testing/selftests/mm/run_vmtests.sh index 45941ad5f658..bf4c4cd46600 100755 --- a/tools/testing/selftests/mm/run_vmtests.sh +++ b/tools/testing/selftests/mm/run_vmtests.sh @@ -223,6 +223,10 @@ CATEGORY="hugetlb" run_test ./hugepage-mremap CATEGORY="hugetlb" run_test ./hugepage-vmemmap CATEGORY="hugetlb" run_test ./hugetlb-madvise +# For this test, we need one and just one huge page +echo 1 > /proc/sys/vm/nr_hugepages +CATEGORY="hugetlb" run_test ./hugetlb_fault_after_madv + if test_selected "hugetlb"; then echo "NOTE: These hugetlb tests provide minimal coverage. Use" echo " https://github.com/libhugetlbfs/libhugetlbfs.git for" -- 2.39.5