lock checking feedback (bug?) 2.6.20(xfs)/i386 during boot

lock checking feedback (bug?) 2.6.20(xfs)/i386 during boot

[Linda Walsh]

Turned on lock testing/proving/deadlock detection.  Not chasing any 
particular
problem, but looking for things "oddities".

Turned on options (under kernel hacking):
   Locking API boot-time self-tests
   RT Mutex debugging, deadlock detection
   Lock debugging: prove locking correctness

Multiple reboots show it to be a constant.
I had tried the new "Asynchronous SCSI scanning" -- thought that might 
have been
related, but turning it off makes no difference.

I'm guessing this "error" has been present before this, but the lock
proving algorithms are bringing it to light?  So I don't know how serious
this is (if it is anything), but at the least, it doesn't look too clean...


Maybe that
....
SCSI device sda: write cache: enabled, read cache: enabled, supports DPO 
and FUA
 sda: sda1 sda2 sda3 sda4 < sda5 sda6 sda7 >
sd 0:0:0:0: Attached scsi disk sda
UDF-fs: No VRS found
XFS mounting filesystem sda3
Ending clean XFS mount for filesystem: sda3
VFS: Mounted root (xfs filesystem) readonly.
Freeing unused kernel memory: 316k freed

=============================================
[ INFO: possible recursive locking detected ]
2.6.20 #3
---------------------------------------------
rm/682 is trying to acquire lock:
 (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0

but task is already holding lock:
 (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0

other info that might help us debug this:
3 locks held by rm/682:
 #0:  (&inode->i_mutex/1){--..}, at: [<b016f946>] do_unlinkat+0x96/0x170
 #1:  (&inode->i_mutex){--..}, at: [<b016db9a>] vfs_unlink+0x5a/0xd0
 #2:  (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0

stack backtrace:
 [<b013aaf1>] __lock_acquire+0xaf1/0xdf0
 [<b013ae47>] lock_acquire+0x57/0x70
 [<b024068d>] xfs_ilock+0x7d/0xb0
 [<b0135d7f>] down_write+0x2f/0x50
 [<b024068d>] xfs_ilock+0x7d/0xb0
 [<b024068d>] xfs_ilock+0x7d/0xb0
 [<b025ff2d>] xfs_lock_dir_and_entry+0xfd/0x100
 [<b0263c68>] xfs_remove+0x198/0x4e0
 [<b025fff6>] xfs_access+0x26/0x50
 [<b025fff6>] xfs_access+0x26/0x50
 [<b016db9a>] vfs_unlink+0x5a/0xd0
 [<b026d8f3>] xfs_vn_unlink+0x23/0x60
 [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
 [<b01398bb>] mark_held_locks+0x6b/0x90
 [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
 [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
 [<b0139a67>] trace_hardirqs_on+0xc7/0x170
 [<b0417f65>] __mutex_lock_slowpath+0x145/0x2a0
 [<b016db9a>] vfs_unlink+0x5a/0xd0
 [<b016d077>] permission+0x137/0x140
 [<b016dbd0>] vfs_unlink+0x90/0xd0
 [<b016f983>] do_unlinkat+0xd3/0x170
 [<b0113807>] do_page_fault+0x327/0x630
 [<b0102fda>] sysenter_past_esp+0x5f/0x99
 =======================
XFS mounting filesystem sda1
Ending clean XFS mount for filesystem: sda1

Re: lock checking feedback (bug?) 2.6.20(xfs)/i386 during boot

[Timothy Shimmin]

Thanks for the report, Linda.
This and other lockdep reports are on our todo/bug list
and I've added this one.
(Nathan looked at some of these lock related changes I believe and we still have
 a pending patch of his to go thru)

--Tim

--On 18 February 2007 1:38:45 PM -0800 Linda Walsh <xfs@tlinx.org> wrote:

> Turned on lock testing/proving/deadlock detection.  Not chasing any particular
> problem, but looking for things "oddities".
>
> Turned on options (under kernel hacking):
>    Locking API boot-time self-tests
>    RT Mutex debugging, deadlock detection
>    Lock debugging: prove locking correctness
>
> Multiple reboots show it to be a constant.
> I had tried the new "Asynchronous SCSI scanning" -- thought that might have been
> related, but turning it off makes no difference.
>
> I'm guessing this "error" has been present before this, but the lock
> proving algorithms are bringing it to light?  So I don't know how serious
> this is (if it is anything), but at the least, it doesn't look too clean...
>
>
> Maybe that
> ....
> SCSI device sda: write cache: enabled, read cache: enabled, supports DPO and FUA
>  sda: sda1 sda2 sda3 sda4 < sda5 sda6 sda7 >
> sd 0:0:0:0: Attached scsi disk sda
> UDF-fs: No VRS found
> XFS mounting filesystem sda3
> Ending clean XFS mount for filesystem: sda3
> VFS: Mounted root (xfs filesystem) readonly.
> Freeing unused kernel memory: 316k freed
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 2.6.20 #3
> ---------------------------------------------
> rm/682 is trying to acquire lock:
>  (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0
>
> but task is already holding lock:
>  (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0
>
> other info that might help us debug this:
> 3 locks held by rm/682:
>  #0:  (&inode->i_mutex/1){--..}, at: [<b016f946>] do_unlinkat+0x96/0x170
>  #1:  (&inode->i_mutex){--..}, at: [<b016db9a>] vfs_unlink+0x5a/0xd0
>  #2:  (&(&ip->i_lock)->mr_lock){----}, at: [<b024068d>] xfs_ilock+0x7d/0xb0
>
> stack backtrace:
>  [<b013aaf1>] __lock_acquire+0xaf1/0xdf0
>  [<b013ae47>] lock_acquire+0x57/0x70
>  [<b024068d>] xfs_ilock+0x7d/0xb0
>  [<b0135d7f>] down_write+0x2f/0x50
>  [<b024068d>] xfs_ilock+0x7d/0xb0
>  [<b024068d>] xfs_ilock+0x7d/0xb0
>  [<b025ff2d>] xfs_lock_dir_and_entry+0xfd/0x100
>  [<b0263c68>] xfs_remove+0x198/0x4e0
>  [<b025fff6>] xfs_access+0x26/0x50
>  [<b025fff6>] xfs_access+0x26/0x50
>  [<b016db9a>] vfs_unlink+0x5a/0xd0
>  [<b026d8f3>] xfs_vn_unlink+0x23/0x60
>  [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
>  [<b01398bb>] mark_held_locks+0x6b/0x90
>  [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
>  [<b0417f72>] __mutex_lock_slowpath+0x152/0x2a0
>  [<b0139a67>] trace_hardirqs_on+0xc7/0x170
>  [<b0417f65>] __mutex_lock_slowpath+0x145/0x2a0
>  [<b016db9a>] vfs_unlink+0x5a/0xd0
>  [<b016d077>] permission+0x137/0x140
>  [<b016dbd0>] vfs_unlink+0x90/0xd0
>  [<b016f983>] do_unlinkat+0xd3/0x170
>  [<b0113807>] do_page_fault+0x327/0x630
>  [<b0102fda>] sysenter_past_esp+0x5f/0x99
>  =======================
> XFS mounting filesystem sda1
> Ending clean XFS mount for filesystem: sda1
> -
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