linux-kernel - [PATCH slab hotfixes 2/2] kunit: move call to kunit_run_all_tests() after rcu_end_inkernel

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Message-Id: <20240930-b4-slub-kunit-fix-v1-2-32ca9dbbbc11@suse.cz>
Date: Mon, 30 Sep 2024 10:37:17 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Andrew Morton <akpm@...ux-foundation.org>, 
 Christoph Lameter <cl@...ux.com>, David Rientjes <rientjes@...gle.com>, 
 Roman Gushchin <roman.gushchin@...ux.dev>, 
 Hyeonggon Yoo <42.hyeyoo@...il.com>, linux-kernel@...r.kernel.org, 
 linux-mm@...ck.org, Vlastimil Babka <vbabka@...e.cz>
Cc: 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 2/2] kunit: move call to
 kunit_run_all_tests() after rcu_end_inkernel_boot()

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.

These tests invoke kfree_rcu() and kvfree_rcu_barrier() 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,
moving the call to kunit_run_all_tests() a bit later in the boot seems
to have fixed the lockup problem according to Guenter's limited testing.

No kunit tests should be broken by calling the built-in executor a bit
later, as when compiled as modules, they are still executed even later
than this.

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>
---
 init/main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index c4778edae7972f512d5eefe8400075ac35a70d1c..7890ebb00e84b8bd7bac28923fb1fe571b3e9ee2 100644
--- a/init/main.c
+++ b/init/main.c
@@ -1489,6 +1489,8 @@ static int __ref kernel_init(void *unused)

 	rcu_end_inkernel_boot();

+	kunit_run_all_tests();
+
 	do_sysctl_args();

 	if (ramdisk_execute_command) {
@@ -1579,8 +1581,6 @@ static noinline void __init kernel_init_freeable(void)

 	do_basic_setup();

-	kunit_run_all_tests();
-
 	wait_for_initramfs();
 	console_on_rootfs();

-- 
2.46.1