lockdep warning on block tree for-2.6.35 branch

lockdep warning on block tree for-2.6.35 branch

[Gui Jianfeng]

Hi

I got the following warning when testing.

INFO: trying to register non-static key.
the code is fine but needs lockdep annotation.
turning off the locking correctness validator.
Pid: 3298, comm: find Not tainted 2.6.34-rc4-Vivek-Blkio #48
Call Trace:
 [<c04558bf>] __lock_acquire+0x166/0x789
 [<c0455f76>] lock_acquire+0x94/0xb1
 [<fa7c06d9>] ? blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
 [<c068e1e2>] _raw_spin_lock_irqsave+0x27/0x5a
 [<fa7c06d9>] ? blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
 [<fa7c06d9>] blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
 [<fa816886>] cfq_insert_request+0xdc/0x4f2 [cfq_iosched]
 [<c0451b48>] ? trace_hardirqs_off+0xb/0xd
 [<c052b7e9>] elv_insert+0xe0/0x174
 [<c052b90c>] __elv_add_request+0x8f/0x94
 [<c05314e2>] __make_request+0x357/0x389
 [<c04d6b44>] ? __find_get_block+0x15d/0x167
 [<c052faa0>] generic_make_request+0x27f/0x321
 [<c0491017>] ? mempool_alloc_slab+0xe/0x10
 [<c0491287>] ? mempool_alloc+0x3c/0xd7
 [<c0531186>] submit_bio+0x8a/0x8f
 [<c04da90a>] ? bio_alloc_bioset+0x37/0x96
 [<c04d656f>] submit_bh+0xf0/0x10f
 [<c04d7556>] ll_rw_block+0xc0/0xf9
 [<f86e717c>] ext3_bread+0x34/0x7b [ext3]
 [<f86ea875>] htree_dirblock_to_tree+0x1f/0x120 [ext3]
 [<f86ea9f0>] ext3_htree_fill_tree+0x7a/0x1bb [ext3]
 [<c0453147>] ? mark_held_locks+0x3d/0x58
 [<c04b29ce>] ? kmem_cache_alloc_notrace+0x86/0xaa
 [<c0453269>] ? trace_hardirqs_on_caller+0x107/0x12f
 [<f86e3b53>] ext3_readdir+0x1f9/0x69e [ext3]
 [<c04c68ec>] ? filldir64+0x0/0xcd
 [<c068d4fe>] ? mutex_lock_killable_nested+0x2c5/0x2d9
 [<c0450b5f>] ? debug_mutex_free_waiter+0x45/0x48
 [<c068d508>] ? mutex_lock_killable_nested+0x2cf/0x2d9
 [<c04c6ac7>] ? vfs_readdir+0x46/0x94
 [<c04c6ae9>] vfs_readdir+0x68/0x94
 [<c04c68ec>] ? filldir64+0x0/0xcd
 [<c04c6b73>] sys_getdents64+0x5e/0x9f
 [<c040274c>] sysenter_do_call+0x12/0x32

Thanks,
Gui

Re: lockdep warning on block tree for-2.6.35 branch

[Divyesh Shah]

Hi Gui,
    Thanks for the report. I can reproduce this and have a patch that
fixes it and makes the warning go away. My understanding of what was
happening is that the stats_lock for the root cfqg was not getting
initialized and hence was missing the static lock_class_key
declaration. This is because we call blkio_group_init() only when
dynamically allocating new cfqg which does not cover the root cfqg.
I'll send out the patch next.

-Divyesh

On Thu, Apr 15, 2010 at 6:40 PM, Gui Jianfeng
<guijianfeng@cn.fujitsu.com> wrote:
> Hi
>
> I got the following warning when testing.
>
> INFO: trying to register non-static key.
> the code is fine but needs lockdep annotation.
> turning off the locking correctness validator.
> Pid: 3298, comm: find Not tainted 2.6.34-rc4-Vivek-Blkio #48
> Call Trace:
>  [<c04558bf>] __lock_acquire+0x166/0x789
>  [<c0455f76>] lock_acquire+0x94/0xb1
>  [<fa7c06d9>] ? blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
>  [<c068e1e2>] _raw_spin_lock_irqsave+0x27/0x5a
>  [<fa7c06d9>] ? blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
>  [<fa7c06d9>] blkiocg_update_io_add_stats+0x21/0xe5 [blk_cgroup]
>  [<fa816886>] cfq_insert_request+0xdc/0x4f2 [cfq_iosched]
>  [<c0451b48>] ? trace_hardirqs_off+0xb/0xd
>  [<c052b7e9>] elv_insert+0xe0/0x174
>  [<c052b90c>] __elv_add_request+0x8f/0x94
>  [<c05314e2>] __make_request+0x357/0x389
>  [<c04d6b44>] ? __find_get_block+0x15d/0x167
>  [<c052faa0>] generic_make_request+0x27f/0x321
>  [<c0491017>] ? mempool_alloc_slab+0xe/0x10
>  [<c0491287>] ? mempool_alloc+0x3c/0xd7
>  [<c0531186>] submit_bio+0x8a/0x8f
>  [<c04da90a>] ? bio_alloc_bioset+0x37/0x96
>  [<c04d656f>] submit_bh+0xf0/0x10f
>  [<c04d7556>] ll_rw_block+0xc0/0xf9
>  [<f86e717c>] ext3_bread+0x34/0x7b [ext3]
>  [<f86ea875>] htree_dirblock_to_tree+0x1f/0x120 [ext3]
>  [<f86ea9f0>] ext3_htree_fill_tree+0x7a/0x1bb [ext3]
>  [<c0453147>] ? mark_held_locks+0x3d/0x58
>  [<c04b29ce>] ? kmem_cache_alloc_notrace+0x86/0xaa
>  [<c0453269>] ? trace_hardirqs_on_caller+0x107/0x12f
>  [<f86e3b53>] ext3_readdir+0x1f9/0x69e [ext3]
>  [<c04c68ec>] ? filldir64+0x0/0xcd
>  [<c068d4fe>] ? mutex_lock_killable_nested+0x2c5/0x2d9
>  [<c0450b5f>] ? debug_mutex_free_waiter+0x45/0x48
>  [<c068d508>] ? mutex_lock_killable_nested+0x2cf/0x2d9
>  [<c04c6ac7>] ? vfs_readdir+0x46/0x94
>  [<c04c6ae9>] vfs_readdir+0x68/0x94
>  [<c04c68ec>] ? filldir64+0x0/0xcd
>  [<c04c6b73>] sys_getdents64+0x5e/0x9f
>  [<c040274c>] sysenter_do_call+0x12/0x32
>
> Thanks,
> Gui
>
>

Re: lockdep warning on block tree for-2.6.35 branch

[Li Zefan]

Divyesh Shah :
> Hi Gui,
>     Thanks for the report. I can reproduce this and have a patch that
> fixes it and makes the warning go away. My understanding of what was
> happening is that the stats_lock for the root cfqg was not getting
> initialized and hence was missing the static lock_class_key
> declaration. This is because we call blkio_group_init() only when
> dynamically allocating new cfqg which does not cover the root cfqg.
> I'll send out the patch next.
> 

We just found out the cause and was about to make a fix. :)

-- Li