On Tue, Aug 31, 2021 at 05:02:15PM +0200, Marco Elver wrote: > On Tue, Aug 31, 2021 at 12:46PM +0200, Marco Elver wrote: > > On Tue, 31 Aug 2021 at 12:13, Heiko Carstens <hca@xxxxxxxxxxxxx> wrote: > I repro'd, and the problem is part QEMU TCG and a minor problem with > stack_trace_save() on s390: > > 1. QEMU TCG doesn't seem to want to execute threads concurrently, > resulting in no "value changes" being observed. This is probably just > a limitation of TCG, and if run on a real CPU, shouldn't be a problem. > On QEMU, most test cases will pass with CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n > (There's one left that requires value changes to be observable) > > 2. stack_trace_save() is subtly broken on s390: it starts the trace in > stack_trace_save() itself. This is incorrect, as the trace should > start with the caller. We reported something similar to arm64, also > because one of our sanitizer tests failed: > https://lkml.kernel.org/r/20210319184106.5688-1-mark.rutland@xxxxxxx ... > I fixed it with the below, and now most tests pass. Note that, other > debugging tools may also report misleading stack traces without the > stack_trace_save() fix (e.g. certain KFENCE reports). > > If you have a better solution for how to fix stack_trace_save() on s390, > please discard my patch. Ah, with your patch I get the below on a real machine; so it looks like this really was the only problem for the failing self tests. Thanks a lot for the patch! Will look into it later and apply if everything else still works! [ 5.138547] ok 1 - test_basic [ 7.538799] ok 2 - test_concurrent_races [ 9.938524] ok 3 - test_novalue_change [ 11.620063] ok 4 - test_novalue_change_exception [ 11.952404] ok 5 - test_unknown_origin [ 14.349852] ok 6 - test_write_write_assume_atomic [ 14.681937] ok 7 - test_write_write_struct [ 15.031046] ok 8 - test_write_write_struct_part [ 17.429869] ok 9 - test_read_atomic_write_atomic [ 17.760862] ok 10 - test_read_plain_atomic_write [ 18.093500] ok 11 - test_read_plain_atomic_rmw [ 20.490570] ok 12 - test_zero_size_access [ 22.939270] ok 13 - test_data_race [ 23.271104] ok 14 - test_assert_exclusive_writer [ 23.601940] ok 15 - test_assert_exclusive_access [ 26.000281] ok 16 - test_assert_exclusive_access_writer [ 26.330718] ok 17 - test_assert_exclusive_bits_change [ 28.739480] ok 18 - test_assert_exclusive_bits_nochange [ 28.962218] ok 19 - test_assert_exclusive_writer_scoped [ 29.071385] ok 20 - test_assert_exclusive_access_scoped [ 31.479706] ok 21 - test_jiffies_noreport [ 33.879581] ok 22 - test_seqlock_noreport [ 36.279853] ok 23 - test_atomic_builtins [ 36.279893] ok 1 - kcsan
