When CONFIG_DEBUG_LOCK_ALLOC is enabled, the following commands can
trigger a bug,
mount -t cgroup2 none /sys/fs/cgroup
cd /sys/fs/cgroup
echo "+hugetlb" > cgroup.subtree_control
The log is as below:
BUG: key ffff8880046d88d8 has not been registered!
------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(1)
WARNING: CPU: 3 PID: 226 at kernel/locking/lockdep.c:4945 lockdep_init_map_type+0x185/0x220
Modules linked in:
CPU: 3 PID: 226 Comm: bash Not tainted 6.10.0-rc4-next-20240617-g76db4c64526c #544
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:lockdep_init_map_type+0x185/0x220
Code: 00 85 c0 0f 84 6c ff ff ff 8b 3d 6a d1 85 01 85 ff 0f 85 5e ff ff ff 48 c7 c6 21 99 4a 82 48 c7 c7 60 29 49 82 e8 3b 2e f5
RSP: 0018:ffffc9000083fc30 EFLAGS: 00000282
RAX: 0000000000000000 RBX: ffffffff828dd820 RCX: 0000000000000027
RDX: ffff88803cd9cac8 RSI: 0000000000000001 RDI: ffff88803cd9cac0
RBP: ffff88800674fbb0 R08: ffffffff828ce248 R09: 00000000ffffefff
R10: ffffffff8285e260 R11: ffffffff828b8eb8 R12: ffff8880046d88d8
R13: 0000000000000000 R14: 0000000000000000 R15: ffff8880067281c0
FS: 00007f68601ea740(0000) GS:ffff88803cd80000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005614f3ebc740 CR3: 000000000773a000 CR4: 00000000000006f0
Call Trace:
<TASK>
? __warn+0x77/0xd0
? lockdep_init_map_type+0x185/0x220
? report_bug+0x189/0x1a0
? handle_bug+0x3c/0x70
? exc_invalid_op+0x18/0x70
? asm_exc_invalid_op+0x1a/0x20
? lockdep_init_map_type+0x185/0x220
__kernfs_create_file+0x79/0x100
cgroup_addrm_files+0x163/0x380
? find_held_lock+0x2b/0x80
? find_held_lock+0x2b/0x80
? find_held_lock+0x2b/0x80
css_populate_dir+0x73/0x180
cgroup_apply_control_enable+0x12f/0x3a0
cgroup_subtree_control_write+0x30b/0x440
kernfs_fop_write_iter+0x13a/0x1f0
vfs_write+0x341/0x450
ksys_write+0x64/0xe0
do_syscall_64+0x4b/0x110
entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7f68602d9833
Code: 8b 15 61 26 0e 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 64 8b 04 25 18 00 00 00 85 c0 75 14 b8 01 00 00 00 08
RSP: 002b:00007fff9bbdf8e8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000009 RCX: 00007f68602d9833
RDX: 0000000000000009 RSI: 00005614f3ebc740 RDI: 0000000000000001
RBP: 00005614f3ebc740 R08: 000000000000000a R09: 0000000000000008
R10: 00005614f3db6ba0 R11: 0000000000000246 R12: 0000000000000009
R13: 00007f68603bd6a0 R14: 0000000000000009 R15: 00007f68603b8880
For lockdep, there is a sanity check in lockdep_init_map_type(), the
lock-class key must either have been allocated statically or must
have been registered as a dynamic key. However the commit e18df2889ff9
("mm/hugetlb_cgroup: prepare cftypes based on template") has changed
the cftypes from static allocated objects to dynamic allocated objects,
so the cft->lockdep_key must be registered proactively.
Fixes: e18df2889ff9 ("mm/hugetlb_cgroup: prepare cftypes based on template")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202406181046.8d8b2492-oliver.sang@xxxxxxxxx
Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
---
v3: remove #ifdef CONFIG_DEBUG_LOCK_ALLOC in struct cftype
v2: add bug log to commit message
---
include/linux/cgroup-defs.h | 2 --
mm/hugetlb_cgroup.c | 2 ++
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index b36690ca0d3f..293af7f8a694 100644
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -681,9 +681,7 @@ struct cftype {
__poll_t (*poll)(struct kernfs_open_file *of,
struct poll_table_struct *pt);
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lock_class_key lockdep_key;
-#endif
};
/*
diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
index 2b899c4ae968..4ff238ba1250 100644
--- a/mm/hugetlb_cgroup.c
+++ b/mm/hugetlb_cgroup.c
@@ -836,6 +836,8 @@ hugetlb_cgroup_cfttypes_init(struct hstate *h, struct cftype *cft,
cft->file_offset = MEMFILE_OFFSET0(offset) +
MEMFILE_FIELD_SIZE(offset) * idx;
}
+
+ lockdep_register_key(&cft->lockdep_key);
}
}
--
2.34.1
