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

[Timothy Shimmin <tes@sgi.com>]

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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