linux-kernel - [PATCH slab hotfixes v2 2/2] slub/kunit: skip test_kfree

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Message-Id: <20241001-b4-slub-kunit-fix-v2-2-2d995d3ecb49@suse.cz>
Date: Tue, 01 Oct 2024 18:20:49 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>
Cc: Roman Gushchin <roman.gushchin@...ux.dev>, 
 Andrew Morton <akpm@...ux-foundation.org>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, Vlastimil Babka <vbabka@...e.cz>, 
 Guenter Roeck <linux@...ck-us.net>, "Paul E. McKenney" <paulmck@...nel.org>, 
 Boqun Feng <boqun.feng@...il.com>, Uladzislau Rezki <urezki@...il.com>, 
 rcu@...r.kernel.org, David Gow <davidgow@...gle.com>, 
 Rae Moar <rmoar@...gle.com>, linux-kselftest@...r.kernel.org, 
 kunit-dev@...glegroups.com, Brendan Higgins <brendan.higgins@...ux.dev>
Subject: [PATCH slab hotfixes v2 2/2] slub/kunit: skip test_kfree_rcu when
 the slub kunit test is built-in

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