From bc2a97ef4b165f7a432cc9cf8d5714b94e120051 Mon Sep 17 00:00:00 2001 From: Edward Liaw Date: Tue, 10 May 2022 18:06:01 +0000 Subject: [PATCH 22/24] userfaultfd: infinite loop in faulting_process The local variables steps and signalled were being reset to 1 and 0 respectively after every jump back to sigsetjmp by siglongjmp in the signal handler. The test was incrementing them and expecting them to retain their incremented values. The documentation for siglongjmp says: All accessible objects have values as of the time sigsetjmp() was called, except that the values of objects of automatic storage duration which are local to the function containing the invocation of the corresponding sigsetjmp() which do not have volatile-qualified type and which are changed between the sigsetjmp() invocation and siglongjmp() call are indeterminate. Tagging steps and signalled with volatile enabled the test to pass. Bug: 232026677 Signed-off-by: Edward Liaw --- tools/testing/selftests/vm/userfaultfd.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c index e7a79f120cbde..b37642be42054 100644 --- a/tools/testing/selftests/vm/userfaultfd.c +++ b/tools/testing/selftests/vm/userfaultfd.c @@ -944,7 +944,7 @@ static int faulting_process(int signal_test) unsigned long split_nr_pages; unsigned long lastnr; struct sigaction act; - unsigned long signalled = 0; + volatile unsigned long signalled = 0; if (test_type != TEST_HUGETLB) split_nr_pages = (nr_pages + 1) / 2; @@ -962,7 +962,7 @@ static int faulting_process(int signal_test) } for (nr = 0; nr < split_nr_pages; nr++) { - int steps = 1; + volatile int steps = 1; unsigned long offset = nr * page_size; if (signal_test) { -- 2.36.0.550.gb090851708-goog