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 <li...@roeck-us.net>
Closes: 
https://lore.kernel.org/all/6fcb1252-7990-4f0d-8027-5e83f0fb9...@roeck-us.net/
Cc: "Paul E. McKenney" <paul...@kernel.org>
Cc: Boqun Feng <boqun.f...@gmail.com>
Cc: Uladzislau Rezki <ure...@gmail.com>
Cc: r...@vger.kernel.org
Cc: Brendan Higgins <brendanhigg...@google.com>
Cc: David Gow <david...@google.com>
Cc: Rae Moar <rm...@google.com>
Cc: linux-kselft...@vger.kernel.org
Cc: kunit-...@googlegroups.com
Signed-off-by: Vlastimil Babka <vba...@suse.cz>
---
 lib/slub_kunit.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/lib/slub_kunit.c b/lib/slub_kunit.c
index 
85d51ec09846d4fa219db6bda336c6f0b89e98e4..80e39f003344858722a544ad62ed84e885574054
 100644
--- a/lib/slub_kunit.c
+++ b/lib/slub_kunit.c
@@ -164,10 +164,16 @@ struct test_kfree_rcu_struct {
 
 static void test_kfree_rcu(struct kunit *test)
 {
-       struct kmem_cache *s = test_kmem_cache_create("TestSlub_kfree_rcu",
-                               sizeof(struct test_kfree_rcu_struct),
-                               SLAB_NO_MERGE);
-       struct test_kfree_rcu_struct *p = kmem_cache_alloc(s, GFP_KERNEL);
+       struct kmem_cache *s;
+       struct test_kfree_rcu_struct *p;
+
+       if (IS_BUILTIN(CONFIG_SLUB_KUNIT_TEST))
+               kunit_skip(test, "can't do kfree_rcu() when test is built-in");
+
+       s = test_kmem_cache_create("TestSlub_kfree_rcu",
+                                  sizeof(struct test_kfree_rcu_struct),
+                                  SLAB_NO_MERGE);
+       p = kmem_cache_alloc(s, GFP_KERNEL);
 
        kfree_rcu(p, rcu);
        kmem_cache_destroy(s);

-- 
2.46.1


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