[bug report v4.8] fs/locks.c: kernel oops during posix lock stress test

[Jeff Layton]

On Mon, 2016-11-28 at 11:10 +0800, Ming Lei wrote:
> Hi Guys,
> 
> When I run stress-ng via the following steps on one ARM64 dual
> socket system(Cavium Thunder), the kernel oops[1] can often be
> triggered after running the stress test for several hours(sometimes
> it may take longer):
> 
> - git clone git://kernel.ubuntu.com/cking/stress-ng.git
> - apply the attachment patch which just makes the posix file
> lock stress test more aggressive
> - run the test via '~/git/stress-ng$./stress-ng --lockf 128 --aggressive'
> 
> 
> From the oops log, looks one garbage file_lock node is got
> from the linked list of 'ctx->flc_posix' when the issue happens.
> 
> BTW, the issue isn't observed on single socket Cavium Thunder yet,
> and the same issue can be seen on Ubuntu Xenial(v4.4 based kernel)
> too.
> 
> Thanks,
> Ming
> 

Some questions just for clarification:

- I assume this is being run on a local fs of some sort? ext4 or xfs or
something?

- have you seen this on any other arch, besides ARM?

The file locking code does do some lockless checking to see whether the
i_flctx is even present and whether the list is empty in
locks_remove_posix. It's possible we have some barrier problems there,
but I don't quite see how that would cause us to have a corrupt lock on
the flc_posix list.

> [1] kernel oops log
> ubuntu at ubuntu:~/git/stress-ng$ ./stress-ng --lockf 128 --aggressive
> stress-ng: info:  [63828] defaulting to a 86400 second run per stressor
> stress-ng: info:  [63828] dispatching hogs: 128 lockf
> stress-ng: info:  [63828] cache allocate: default cache size: 16384K
> [80659.799092] Unable to handle kernel NULL pointer dereference at
> virtual address 00000030
> [80659.807219] pgd = ffff81001f365800
> [80659.810683] [00000030] *pgd=000001001a290003,
> *pud=000001001a290003, *pmd=0000010fa07f0003, *pte=0000000000000000
> [80659.821029] Internal error: Oops: 96000007 [#1] SMP
> [80659.825901] Modules linked in:
> [80659.828962] CPU: 15 PID: 63848 Comm: stress-ng-lockf Tainted: G
>    W       4.8.0 #167
> [80659.837132] Hardware name: Cavium ThunderX CRB/To be filled by
> O.E.M., BIOS 5.11 12/12/2012
> [80659.845479] task: ffff81001ee78580 task.stack: ffff81001f798000
> [80659.851402] PC is at posix_locks_conflict+0x94/0xc0
> [80659.856282] LR is at posix_lock_inode+0x90/0x6b0
> [80659.860896] pc : [<ffff00000828c694>] lr : [<ffff00000828cd90>]
> pstate: a0000145
> [80659.868285] sp : ffff81001f79bca0
> [80659.871596] x29: ffff81001f79bca0 x28: ffff81001f798000
> [80659.876915] x27: ffff800fdffbc160 x26: 0000000000000000
> [80659.882234] x25: ffff800fd2da2b30 x24: ffff800fce927430
> [80659.887551] x23: ffff800fce92d8f0 x22: ffff81001f79bd30
> [80659.892869] x21: ffff800fd2da2b18 x20: fffffffffffffff8
> [80659.898187] x19: ffff800fdffbc160 x18: 0000000000001140
> [80659.903504] x17: 0000ffff8870a578 x16: ffff000008245768
> [80659.908821] x15: 0000ffff888bc000 x14: 0000000000000000
> [80659.914139] x13: 00000003e8000000 x12: 0000000000000018
> [80659.919457] x11: 00000000000e6a17 x10: 00000000ffffffd0
> [80659.924776] x9 : 0000000000000000 x8 : ffff800fce927500
> [80659.930094] x7 : 0000000000000000 x6 : 000000000000007f
> [80659.935413] x5 : 0000000000000080 x4 : ffff800fce927438
> [80659.940729] x3 : ffff800fce927458 x2 : 00000000000026b9
> [80659.946047] x1 : ffff81001f37f300 x0 : 0000000000000000
> [80659.951363]
> [80659.952851] Process stress-ng-lockf (pid: 63848, stack limit =
> 0xffff81001f798020)
> [80659.960415] Stack: (0xffff81001f79bca0 to 0xffff81001f79c000)
> [80659.966158] bca0: ffff81001f79bcc0 ffff00000828cd90
> fffffffffffffff8 ffff800fa3a66568
> [80659.973986] bcc0: ffff81001f79bd40 ffff00000828d5f0
> ffff800f8185c700 ffff800fdffbc160
> [80659.981812] bce0: 0000000000000006 0000000000000000
> ffff81001f79bdd0 0000000000000006
> [80659.989638] bd00: 0000000000000120 0000000000000019
> ffff0000088b1000 ffff81001f798000
> [80659.997465] bd20: ffff81001f79bd40 ffff000008403fec
> ffff81001f79bd30 ffff81001f79bd30
> [80660.005292] bd40: ffff81001f79bd70 ffff00000828d8bc
> ffff800f8185c700 ffff800fdffbc160
> [80660.013118] bd60: ffff800fdffbc1b8 ffff800f8185c700
> ffff81001f79bde0 ffff00000828ef10
> [80660.020944] bd80: ffff800f8185c700 0000000000000000
> ffff800fdffbc160 ffff800fa3a66568
> [80660.028770] bda0: 0000000000000006 0000000000000004
> ffff81001f79bde0 ffff00000828ee14
> [80660.036596] bdc0: ffff800f8185c700 00000000fffffff2
> ffff800fdffbc160 ffff810ff99aae80
> [80660.044423] bde0: ffff81001f79be70 ffff000008245b84
> ffff800f8185c700 ffff800f8185c700
> [80660.052249] be00: 0000000000000000 0000000000000006
> 0000ffffdad5d4b0 0000000000000004
> [80660.060087] be20: 0000000000000120 000000000000003e
> 0000000000010001 0000000000000000
> [80660.067916] be40: 0000000000000008 0000000000000000
> 0000000000010001 0000000000000000
> [80660.075742] be60: 0000000000000008 0000000000000000
> 0000000000000000 ffff0000080836f0
> [80660.083568] be80: 0000000000000000 00000000005c5000
> ffffffffffffffff 0000ffff8870a3b8
> [80660.091394] bea0: 0000000080000000 0000000000000015
> 0000000080000000 00000000005c5000
> [80660.099220] bec0: 0000000000000004 0000000000000006
> 0000ffffdad5d4b0 00000000ffffff80
> [80660.107046] bee0: 0000ffffdad5d490 0000000026c26373
> 000000000000176f 0000000000004650
> [80660.114873] bf00: 0000000000000019 0000000000006536
> 00000000ffffffd0 00000000000e6a17
> [80660.122698] bf20: 0000000000000018 00000003e8000000
> 0000000000000000 0000ffff888bc000
> [80660.130524] bf40: 000000000048a170 0000ffff8870a578
> 0000000000001140 000000000000055f
> [80660.138351] bf60: 00000000005c5000 0000000000000004
> 0000ffff879f9008 0000000000000000
> [80660.146177] bf80: 0000000000000002 000000000048b530
> 2001000800400201 0000ffffdad60758
> [80660.154004] bfa0: 000000000048b008 0000ffffdad5d390
> 0000ffff8870a518 0000ffffdad5d390
> [80660.161830] bfc0: 0000ffff8870a3b8 0000000080000000
> 0000000000000004 0000000000000019
> [80660.169656] bfe0: 0000000000000000 0000000000000000
> 0000000000000000 0000000000000000
> [80660.177481] Call trace:
> [80660.179928] Exception stack(0xffff81001f79bad0 to 0xffff81001f79bc00)
> [80660.186365] bac0:
> ffff800fdffbc160 0001000000000000
> [80660.194192] bae0: ffff81001f79bca0 ffff00000828c694
> ffff800fc0002c00 ffff81001ee78600
> [80660.202017] bb00: ffff81001f79bb70 ffff00000820b57c
> ffff800fcb2a6d88 ffff800fc0002c00
> [80660.209843] bb20: 0000000000000001 ffff810008ddbf00
> ffff81001f79bc30 ffff81001f79bc30
> [80660.217670] bb40: 0000000000000000 ffff810fa0712be8
> ffff800f81dfd680 ffff810fa0712be8
> [80660.225496] bb60: 0000000000000001 ffff810008ddbf00
> 0000000000000000 ffff81001f37f300
> [80660.233322] bb80: 00000000000026b9 ffff800fce927458
> ffff800fce927438 0000000000000080
> [80660.241148] bba0: 000000000000007f 0000000000000000
> ffff800fce927500 0000000000000000
> [80660.248974] bbc0: 00000000ffffffd0 00000000000e6a17
> 0000000000000018 00000003e8000000
> [80660.256800] bbe0: 0000000000000000 0000ffff888bc000
> ffff000008245768 0000ffff8870a578
> [80660.264636] [<ffff00000828c694>] posix_locks_conflict+0x94/0xc0
> [80660.270559] [<ffff00000828cd90>] posix_lock_inode+0x90/0x6b0
> [80660.276220] [<ffff00000828d5f0>] vfs_lock_file+0x68/0x78
> [80660.281537] [<ffff00000828d8bc>] do_lock_file_wait+0x54/0xe0
> [80660.287199] [<ffff00000828ef10>] fcntl_setlk+0x1c0/0x308
> [80660.292513] [<ffff000008245b84>] SyS_fcntl+0x41c/0x5b8
> [80660.297653] [<ffff0000080836f0>] el0_svc_naked+0x24/0x28
> [80660.302961] Code: a8c27bfd d65f03c0 d503201f f9401e61 (f9401e80)
> [80660.309188] ---[ end trace aa50050684d3a3fe ]---

-- 
Jeff Layton <jlayton at poochiereds.net>