Re: [PATCH slab hotfixes v2 2/2] slub/kunit: skip test_kfree_rcu when the slub kunit test is built-in

[Guenter Roeck]

On 10/1/24 09:20, Vlastimil Babka wrote:
> Guenter Roeck reports that the new slub kunit tests added by commit
> 4e1c44b3db79 ("kunit, slub: add test_kfree_rcu() and
> test_leak_destroy()") cause a lockup on boot on several architectures
> when the kunit tests are configured to be built-in and not modules.
>
> The test_kfree_rcu test invokes kfree_rcu() and boot sequence inspection
> showed the runner for built-in kunit tests kunit_run_all_tests() is
> called before setting system_state to SYSTEM_RUNNING and calling
> rcu_end_inkernel_boot(), so this seems like a likely cause. So while I
> was unable to reproduce the problem myself, skipping the test when the
> slub_kunit module is built-in should avoid the issue.
>
> An alternative fix that was moving the call to kunit_run_all_tests() a
> bit later in the boot was tried, but has broken tests with functions
> marked as __init due to free_initmem() already being done.
>
> Fixes: 4e1c44b3db79 ("kunit, slub: add test_kfree_rcu() and test_leak_destroy()")
> Reported-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Closes: https://lore.kernel.org/all/6fcb1252-7990-4f0d-8027-5e83f0fb9409@xxxxxxxxxxxx/
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
> Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
> Cc: Uladzislau Rezki <urezki@xxxxxxxxx>
> Cc: rcu@xxxxxxxxxxxxxxx
> Cc: Brendan Higgins <brendanhiggins@xxxxxxxxxx>
> Cc: David Gow <davidgow@xxxxxxxxxx>
> Cc: Rae Moar <rmoar@xxxxxxxxxx>
> Cc: linux-kselftest@xxxxxxxxxxxxxxx
> Cc: kunit-dev@xxxxxxxxxxxxxxxx
> Signed-off-by: Vlastimil Babka <vbabka@xxxxxxx>

This results in:

    KTAP version 1
    # Subtest: slub_test
    # module: slub_kunit
    1..8
    # test_clobber_zone: pass:1 fail:0 skip:0 total:1
    ok 1 test_clobber_zone
    # test_next_pointer: pass:1 fail:0 skip:0 total:1
    ok 2 test_next_pointer
    # test_first_word: pass:1 fail:0 skip:0 total:1
    ok 3 test_first_word
    # test_clobber_50th_byte: pass:1 fail:0 skip:0 total:1
    ok 4 test_clobber_50th_byte
    # test_clobber_redzone_free: pass:1 fail:0 skip:0 total:1
    ok 5 test_clobber_redzone_free
    # test_kmalloc_redzone_access: pass:1 fail:0 skip:0 total:1
    ok 6 test_kmalloc_redzone_access
    # test_kfree_rcu: pass:0 fail:0 skip:1 total:1
    ok 7 test_kfree_rcu # SKIP can't do kfree_rcu() when test is built-in
    # test_leak_destroy: pass:1 fail:0 skip:0 total:1
    ok 8 test_leak_destroy
# slub_test: pass:7 fail:0 skip:1 total:8

Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>

Thanks,
Guenter