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

[Guenter Roeck <linux@roeck-us.net>]

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@roeck-us.net>
> Closes: https://lore.kernel.org/all/6fcb1252-7990-4f0d-8027-5e83f0fb9409@roeck-us.net/
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Boqun Feng <boqun.feng@gmail.com>
> Cc: Uladzislau Rezki <urezki@gmail.com>
> Cc: rcu@vger.kernel.org
> Cc: Brendan Higgins <brendanhiggins@google.com>
> Cc: David Gow <davidgow@google.com>
> Cc: Rae Moar <rmoar@google.com>
> Cc: linux-kselftest@vger.kernel.org
> Cc: kunit-dev@googlegroups.com
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

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@roeck-us.net>

Thanks,
Guenter