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* "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key"
@ 2020-05-15  5:21 Qian Cai
  2020-05-17  1:15 ` Waiman Long
  0 siblings, 1 reply; 3+ messages in thread
From: Qian Cai @ 2020-05-15  5:21 UTC (permalink / raw)
  To: Peter Zijlstra, Will Deacon, Ingo Molnar
  Cc: David Howells, Alexander Viro, linux-fsdevel,
	Linux Kernel Mailing List, Waiman Long

Lockdep is screwed here in next-20200514 due to "BUG: MAX_LOCKDEP_ENTRIES too low". One of the traces below pointed to this linux-next commit,

8c8e824d4ef0 watch_queue: Introduce a non-repeating system-unique superblock ID

which was accidentally just showed up in next-20200514 along with,

46896d79c514 watch_queue: Add superblock notifications

I did have here,

CONFIG_SB_NOTIFICATIONS=y
CONFIG_MOUNT_NOTIFICATIONS=y
CONFIG_FSINFO=y

While MAX_LOCKDEP_ENTRIES is 32768, I noticed there is one type of lock had a lot along,

# grep  'type->s_umount_key’ /proc/lockdep_chains | wc -l
6979

type->s_umount_key is from alloc_super(),

lockdep_set_class(&s->s_umount, &type->s_umount_key);

Any thought before I bury myself bisecting this?

[15323.316234] LTP: starting isofs (isofs.sh)
[15369.549302] LTP: starting fs_fill
[15369.837565] /dev/zero: Can't open blockdev
[15378.107150] EXT4-fs (loop0): mounting ext3 file system using the ext4 subsystem
[15378.180704] EXT4-fs (loop0): mounted filesystem with ordered data mode. Opts: (null)
[15378.191630] ext3 filesystem being mounted at /tmp/ltp-M6YHxqgN9o/mIisOB/mntpoint supports timestamps until 2038 (0x7fffffff)
[15448.581853] EXT4-fs (loop0): mounted filesystem with ordered data mode. Opts: (null)
[15448.592515] ext4 filesystem being mounted at /tmp/ltp-M6YHxqgN9o/mIisOB/mntpoint supports timestamps until 2038 (0x7fffffff)
[15482.370368] XFS (loop0): Mounting V5 Filesystem
[15482.413544] XFS (loop0): Ending clean mount
[15482.427896] xfs filesystem being mounted at /tmp/ltp-M6YHxqgN9o/mIisOB/mntpoint supports timestamps until 2038 (0x7fffffff)
[15495.280716] XFS (loop0): Unmounting Filesystem
[15613.223513] LTP: starting binfmt_misc01 (binfmt_misc01.sh)
[15615.253089] BUG: MAX_LOCKDEP_ENTRIES too low!
[15615.258178] turning off the locking correctness validator.
[15615.264402] CPU: 4 PID: 80930 Comm: mount Tainted: G           O      5.7.0-rc5-next-20200514 #1
[15615.273942] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
[15615.283218] Call Trace:
[15615.286388]  dump_stack+0xa7/0xea
[15615.290429]  alloc_list_entry.cold.37+0x11/0x18
[15615.295689]  __lock_acquire+0x2aad/0x3260
[15615.300428]  ? register_lock_class+0xb90/0xb90
[15615.305603]  ? __kasan_check_read+0x11/0x20
[15615.310514]  ? mark_lock+0x160/0xfe0
[15615.314814]  ? check_chain_key+0x1df/0x2e0
[15615.319637]  ? print_irqtrace_events+0x110/0x110
[15615.324984]  lock_acquire+0x1a2/0x680
[15615.329373]  ? vfs_generate_unique_id+0x23/0x70
[15615.334632]  ? check_flags.part.28+0x220/0x220
[15615.339806]  ? ktime_get+0xf2/0x150
[15615.344016]  ? lockdep_hardirqs_on+0x1b0/0x2c0
[15615.349190]  ? vfs_generate_unique_id+0x14/0x70
[15615.354453]  ? trace_hardirqs_on+0x3a/0x160
[15615.359366]  _raw_spin_lock+0x2f/0x40
[15615.363754]  ? vfs_generate_unique_id+0x23/0x70
[15615.369014]  vfs_generate_unique_id+0x23/0x70
vfs_generate_unique_id at fs/super.c:1890
[15615.374099]  alloc_super+0x531/0x5b0
alloc_super at fs/super.c:286
[15615.378398]  ? alloc_file.cold.7+0x19/0x19
[15615.383220]  sget_fc+0xb9/0x3a0
sget_fc at fs/super.c:539
[15615.387082]  ? compare_single+0x10/0x10
[15615.391645]  ? bm_get_tree+0x20/0x20 [binfmt_misc]
[15615.397167]  vfs_get_super+0x4e/0x1a0
vfs_get_super at fs/super.c:1197
[15615.401554]  get_tree_single+0x13/0x20
[15615.406031]  bm_get_tree+0x15/0x20 [binfmt_misc]
[15615.411380]  vfs_get_tree+0x54/0x150
[15615.415681]  do_mount+0xef4/0x11b0
[15615.419807]  ? copy_mount_string+0x20/0x20
[15615.424630]  ? __kasan_check_write+0x14/0x20
[15615.429630]  ? _copy_from_user+0x95/0xd0
[15615.434282]  ? memdup_user+0x58/0x90
[15615.438579]  __x64_sys_mount+0x100/0x120
[15615.443231]  do_syscall_64+0xcc/0xaf0
[15615.447617]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[15615.452965]  ? syscall_return_slowpath+0x580/0x580
[15615.458487]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xb3
[15615.464447]  ? trace_hardirqs_off_caller+0x3a/0x150
[15615.470055]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[15615.475489]  entry_SYSCALL_64_after_hwframe+0x49/0xb3
[15615.481271] RIP: 0033:0x7f9721fb79ee
[15615.485572] Code: 48 8b 0d 9d f4 2b 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 6a f4 2b 00 f7 d8 64 89 01 48
[15615.505155] RSP: 002b:00007ffd555d4ac8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
[15615.513474] RAX: ffffffffffffffda RBX: 00005591d34c19c0 RCX: 00007f9721fb79ee
[15615.521355] RDX: 00005591d34c1ba0 RSI: 00005591d34c38c0 RDI: 00005591d34c1bc0
[15615.529232] RBP: 00007f9722d63184 R08: 0000000000000000 R09: 0000000000000003
[15615.537113] R10: 00000000c0ed0000 R11: 0000000000000246 R12: 0000000000000000
[15615.544991] R13: 00000000c0ed0000 R14: 00005591d34c1bc0 R15: 00005591d34c1ba0

=== the second run ===

[28392.003312] LTP: starting read_all_dev (read_all -d /dev -p -q -r 10)
[28392.125739] BUG: MAX_LOCKDEP_ENTRIES too low!
[28392.131254] turning off the locking correctness validator.
[28392.137568] CPU: 64 PID: 107055 Comm: read_all Tainted: G           O L    5.7.0-rc5-next-20200514 #1
[28392.147634] Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40 07/10/2019
[28392.157002] Call Trace:
[28392.160260]  dump_stack+0xa7/0xea
[28392.164390]  alloc_list_entry.cold.37+0x11/0x18
[28392.169745]  __lock_acquire+0x2aad/0x3260
[28392.174820]  ? register_lock_class+0xb90/0xb90
[28392.180208]  ? check_chain_key+0x1df/0x2e0
[28392.185120]  lock_acquire+0x1a2/0x680
[28392.189646]  ? get_random_u32+0x4c/0xe0
[28392.194296]  ? lock_downgrade+0x3e0/0x3e0
[28392.199123]  ? check_flags.part.28+0x220/0x220
[28392.204386]  ? get_random_u32+0x4c/0xe0
[28392.209038]  _raw_spin_lock_irqsave+0x3a/0x50
[28392.214212]  ? get_random_u32+0x4c/0xe0
[28392.218862]  get_random_u32+0x4c/0xe0
get_random_u32 at drivers/char/random.c:2225
[28392.223341]  allocate_slab+0x13e/0x5c0
[28392.227905]  ? memcg_kmem_get_cache+0x378/0x640
[28392.233257]  new_slab+0x46/0x70
[28392.237207]  ___slab_alloc+0x35e/0x810
[28392.241770]  ? rcu_read_lock_sched_held+0xe0/0xe0
[28392.247295]  ? seq_open+0x44/0xd0
[28392.251424]  ? seq_open+0x44/0xd0
[28392.255551]  __slab_alloc+0x43/0x70
[28392.259851]  ? __slab_alloc+0x43/0x70
[28392.264325]  ? seq_open+0x44/0xd0
[28392.268455]  kmem_cache_alloc+0x2e9/0x460
[28392.273281]  seq_open+0x44/0xd0
kmem_cache_zalloc at include/linux/slab.h:661 (discriminator 3)
(inlined by) seq_open at fs/seq_file.c:59 (discriminator 3)
[28392.277233]  kernfs_fop_open+0x2ec/0x720
[28392.281973]  do_dentry_open+0x323/0x870
do_dentry_open at fs/open.c:796
[28392.286625]  ? kernfs_fop_read+0x2c0/0x2c0
[28392.291539]  ? chmod_common+0x280/0x280
[28392.296188]  ? kernfs_iop_permission+0x5d/0x70
[28392.301451]  ? inode_permission+0x65/0x1d0
[28392.306364]  vfs_open+0x58/0x60
[28392.310314]  path_openat+0xbd6/0xf40
[28392.314703]  ? path_lookupat+0x1c0/0x1c0
[28392.319441]  ? register_lock_class+0xb90/0xb90
[28392.324701]  ? match_held_lock+0x20/0x270
[28392.329525]  ? match_held_lock+0x20/0x270
[28392.334351]  ? check_chain_key+0x1df/0x2e0
[28392.339261]  ? find_held_lock+0xca/0xf0
[28392.343910]  do_filp_open+0x11d/0x1a0
[28392.348389]  ? may_open_dev+0x50/0x50
[28392.352865]  ? __kasan_check_read+0x11/0x20
[28392.357866]  ? do_raw_spin_unlock+0xa8/0x140
[28392.362953]  ? _raw_spin_unlock+0x22/0x30
[28392.367780]  do_sys_openat2+0x307/0x420
[28392.372431]  ? file_open_root+0x210/0x210
[28392.377257]  do_sys_open+0x95/0xe0
[28392.381469]  ? filp_open+0x60/0x60
[28392.385683]  ? lockdep_hardirqs_on+0x1b0/0x2c0
[28392.390944]  __x64_sys_openat+0x59/0x70
[28392.395596]  do_syscall_64+0xcc/0xaf0
[28392.400072]  ? trace_hardirqs_on_thunk+0x1a/0x1c
[28392.405510]  ? syscall_return_slowpath+0x580/0x580
[28392.411122]  ? entry_SYSCALL_64_after_hwframe+0x3e/0xb3
[28392.417172]  ? trace_hardirqs_off_caller+0x3a/0x150
[28392.422869]  ? trace_hardirqs_off_thunk+0x1a/0x1c
[28392.428394]  entry_SYSCALL_64_after_hwframe+0x49/0xb3
[28392.434268] RIP: 0033:0x7f1ad727a2ff
[28392.438658] Code: 52 89 f0 25 00 00 41 00 3d 00 00 41 00 74 44 8b 05 56 d1 20 00 85 c0 75 65 89 f2 b8 01 01 00 00 48 89 fe bf 9c ff ff ff 0f 05 <48> 3d 00 f0 ff ff 0f 87 9d 00 00 00 48 8b 4c 24 28 64 48 33 0c 25
[28392.458331] RSP: 002b:00007ffd8c461340 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
[28392.466742] RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00007f1ad727a2ff
[28392.474710] RDX: 0000000000000800 RSI: 00007ffd8c461450 RDI: 00000000ffffff9c

^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key"
  2020-05-15  5:21 "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key" Qian Cai
@ 2020-05-17  1:15 ` Waiman Long
  2020-05-17 11:12   ` Qian Cai
  0 siblings, 1 reply; 3+ messages in thread
From: Waiman Long @ 2020-05-17  1:15 UTC (permalink / raw)
  To: Qian Cai, Peter Zijlstra, Will Deacon, Ingo Molnar
  Cc: David Howells, Alexander Viro, linux-fsdevel, Linux Kernel Mailing List

On 5/15/20 1:21 AM, Qian Cai wrote:
> Lockdep is screwed here in next-20200514 due to "BUG: MAX_LOCKDEP_ENTRIES too low". One of the traces below pointed to this linux-next commit,
>
> 8c8e824d4ef0 watch_queue: Introduce a non-repeating system-unique superblock ID
>
> which was accidentally just showed up in next-20200514 along with,
>
> 46896d79c514 watch_queue: Add superblock notifications
>
> I did have here,
>
> CONFIG_SB_NOTIFICATIONS=y
> CONFIG_MOUNT_NOTIFICATIONS=y
> CONFIG_FSINFO=y
>
> While MAX_LOCKDEP_ENTRIES is 32768, I noticed there is one type of lock had a lot along,
>
> # grep  'type->s_umount_key’ /proc/lockdep_chains | wc -l
> 6979

The lock_list table entries are for tracking a lock's forward and 
backward dependencies. The lockdep_chains isn't the right lockdep file 
to look at. Instead, check the lockdep files for entries with the 
maximum BD (backward dependency) + FD (forward dependency). That will 
give you a better view of which locks are consuming most of the 
lock_list entries. Also take a look at lockdep_stats for an overall view 
of how much various table entries are being consumed.

Cheers,
Longman



^ permalink raw reply	[flat|nested] 3+ messages in thread

* Re: "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key"
  2020-05-17  1:15 ` Waiman Long
@ 2020-05-17 11:12   ` Qian Cai
  0 siblings, 0 replies; 3+ messages in thread
From: Qian Cai @ 2020-05-17 11:12 UTC (permalink / raw)
  To: Waiman Long
  Cc: Peter Zijlstra, Will Deacon, Ingo Molnar, David Howells,
	Alexander Viro, linux-fsdevel, Linux Kernel Mailing List



> On May 16, 2020, at 9:16 PM, Waiman Long <longman@redhat.com> wrote:
> 
> The lock_list table entries are for tracking a lock's forward and backward dependencies. The lockdep_chains isn't the right lockdep file to look at. Instead, check the lockdep files for entries with the maximum BD (backward dependency) + FD (forward dependency). That will give you a better view of which locks are consuming most of the lock_list entries. Also take a look at lockdep_stats for an overall view of how much various table entries are being consumed.

Thanks for the hint. It seems something in vfs is the culprit because every single one of those triggering from path_openat() (vfs_open()) or vfs_get_tree()

When the system after boot, lock_list entries is around 10000. After running LTP syscalls and mm tests, the number is around 20000. Then, it will go all the way over the max (32700) while running LTP fs tests. Most of the time from a test that would read every single file in sysfs.

I’ll decode the lockdep file to see if there is any more clues.

^ permalink raw reply	[flat|nested] 3+ messages in thread

end of thread, other threads:[~2020-05-17 11:13 UTC | newest]

Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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2020-05-15  5:21 "BUG: MAX_LOCKDEP_ENTRIES too low" with 6979 "&type->s_umount_key" Qian Cai
2020-05-17  1:15 ` Waiman Long
2020-05-17 11:12   ` Qian Cai

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