> On Thu, Jan 04, 2007 at 10:02:00PM -0800, Andrew Morton wrote:
> >
> >
ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20-rc3/2.6.20-rc3-mm1/
> >
> Hi,
>
> Lockdep issues the following warning:
> [ 9.064000] =============================================
> [ 9.064000] [ INFO: possible recursive locking detected ]
> [ 9.064000] 2.6.20-rc3-mm1 #3
> [ 9.064000] ---------------------------------------------
> [ 9.064000] init/1 is trying to acquire lock:
> [ 9.064000] (&sysfs_inode_imutex_key){--..}, at: [<c03e6afc>] mutex_lock+0x1c/0x1f
> [ 9.064000]
> [ 9.064000] but task is already holding lock:
> [ 9.064000] (&sysfs_inode_imutex_key){--..}, at: [<c03e6afc>] mutex_lock+0x1c/0x1f
> [ 9.065000]
> [ 9.065000] other info that might help us debug this:
> [ 9.065000] 2 locks held by init/1:
> [ 9.065000] #0: (tty_mutex){--..}, at: [<c03e6afc>] mutex_lock+0x1c/0x1f
> [ 9.065000] #1: (&sysfs_inode_imutex_key){--..}, at: [<c03e6afc>] mutex_lock+0x1c/0x1f
> [ 9.065000]
> [ 9.065000] stack backtrace:
> [ 9.065000] [<c010390d>] show_trace_log_lvl+0x1a/0x30
> [ 9.066000] [<c0103935>] show_trace+0x12/0x14
> [ 9.066000] [<c0103a2f>] dump_stack+0x16/0x18
> [ 9.066000] [<c0138cb8>] print_deadlock_bug+0xb9/0xc3
> [ 9.066000] [<c0138d17>] check_deadlock+0x55/0x5a
> [ 9.066000] [<c013a953>] __lock_acquire+0x371/0xbf0
> [ 9.066000] [<c013b7a9>] lock_acquire+0x69/0x83
> [ 9.066000] [<c03e6b7e>] __mutex_lock_slowpath+0x75/0x2d1
> [ 9.066000] [<c03e6afc>] mutex_lock+0x1c/0x1f
> [ 9.066000] [<c01b249c>] sysfs_drop_dentry+0xb1/0x133
> [ 9.066000] [<c01b25d1>] sysfs_hash_and_remove+0xb3/0x142
> [ 9.066000] [<c01b30ed>] sysfs_remove_file+0xd/0x10
> [ 9.067000] [<c02849e0>] device_remove_file+0x23/0x2e
> [ 9.067000] [<c02850b2>] device_del+0x188/0x1e6
> [ 9.067000] [<c028511b>] device_unregister+0xb/0x15
> [ 9.067000] [<c0285318>] device_destroy+0x9c/0xa9
> [ 9.067000] [<c0261431>] vcs_remove_sysfs+0x1c/0x3b
> [ 9.067000] [<c0267a08>] con_close+0x5e/0x6b
> [ 9.067000] [<c02598f2>] release_dev+0x4c4/0x6e5
> [ 9.067000] [<c0259faa>] tty_release+0x12/0x1c
> [ 9.067000] [<c0174872>] __fput+0x177/0x1a0
> [ 9.067000] [<c01746f5>] fput+0x3b/0x41
> [ 9.068000] [<c0172ee1>] filp_close+0x36/0x65
> [ 9.068000] [<c0172f73>] sys_close+0x63/0xa4
> [ 9.068000] [<c0102a96>] sysenter_past_esp+0x5f/0x99
> [ 9.068000] =======================
>
> This is due to sysfs_hash_and_remove() holding dir->d_inode->i_mutex
> before calling sysfs_drop_dentry() which calls orphan_all_buffers()
> which in turn takes node->i_mutex.
> The following patch solves the problem by defering the buffers orphaning
> after the dir->d_inode->imutex is released. Not sure it's the best
> solution though, better wait for feedback from Maneesh and Oliver.
