Running with lockdep I see these warnings (running 2.6.37-rc1)
It occurred during the time when rsync is running backup.
Nov 14 12:03:31 nehalam kernel: [ 5527.284541]
=============================================
Nov 14 12:03:31 nehalam kernel: [ 5527.284544] [ INFO: possible recursive
locking detected ]
Nov 14 12:03:31 nehalam kernel: [ 5527.284546] 2.6.37-rc1+ #67
Nov 14 12:03:31 nehalam kernel: [ 5527.284547]
---------------------------------------------
Nov 14 12:03:31 nehalam kernel: [ 5527.284549] rsync/2782 is trying to acquire
lock:
Nov 14 12:03:31 nehalam kernel: [ 5527.284551] (&(&eb->lock)->rlock){+.+...},
at: [<ffffffffa005f026>] btrfs_try_spin_lock+0x53/0xd1 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284567]
Nov 14 12:03:31 nehalam kernel: [ 5527.284567] but task is already holding lock:
Nov 14 12:03:31 nehalam kernel: [ 5527.284569] (&(&eb->lock)->rlock){+.+...},
at: [<ffffffffa005f0c6>] btrfs_clear_lock_blocking+0x22/0x2c [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284581]
Nov 14 12:03:31 nehalam kernel: [ 5527.284581] other info that might help us
debug this:
Nov 14 12:03:31 nehalam kernel: [ 5527.284583] 2 locks held by rsync/2782:
Nov 14 12:03:31 nehalam kernel: [ 5527.284585] #0:
(&sb->s_type->i_mutex_key#13){+.+.+.}, at: [<ffffffff810f98be>]
do_lookup+0x9d/0x10d
Nov 14 12:03:31 nehalam kernel: [ 5527.284592] #1:
(&(&eb->lock)->rlock){+.+...}, at: [<ffffffffa005f0c6>]
btrfs_clear_lock_blocking+0x22/0x2c [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284605]
Nov 14 12:03:31 nehalam kernel: [ 5527.284605] stack backtrace:
Nov 14 12:03:31 nehalam kernel: [ 5527.284607] Pid: 2782, comm: rsync Not
tainted 2.6.37-rc1+ #67
Nov 14 12:03:31 nehalam kernel: [ 5527.284609] Call Trace:
Nov 14 12:03:31 nehalam kernel: [ 5527.284615] [<ffffffff8106b651>]
__lock_acquire+0xc7a/0xcf1
Nov 14 12:03:31 nehalam kernel: [ 5527.284619] [<ffffffff810ba186>] ?
activate_page+0x130/0x13f
Nov 14 12:03:31 nehalam kernel: [ 5527.284622] [<ffffffff8106b799>]
lock_acquire+0xd1/0xf7
Nov 14 12:03:31 nehalam kernel: [ 5527.284633] [<ffffffffa005f026>] ?
btrfs_try_spin_lock+0x53/0xd1 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284638] [<ffffffff813b31c7>]
_raw_spin_lock+0x31/0x40
Nov 14 12:03:31 nehalam kernel: [ 5527.284648] [<ffffffffa005f026>] ?
btrfs_try_spin_lock+0x53/0xd1 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284659] [<ffffffffa005f0c6>] ?
btrfs_clear_lock_blocking+0x22/0x2c [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284669] [<ffffffffa005f026>]
btrfs_try_spin_lock+0x53/0xd1 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284677] [<ffffffffa0022714>]
btrfs_search_slot+0x3e6/0x513 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284687] [<ffffffffa003121f>]
btrfs_lookup_inode+0x2f/0x8f [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284698] [<ffffffffa003ac58>] ?
btrfs_init_locked_inode+0x0/0x2e [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284709] [<ffffffffa003e2a7>]
btrfs_iget+0xc3/0x415 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284721] [<ffffffffa00419b9>]
btrfs_lookup_dentry+0x105/0x3c4 [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284724] [<ffffffff81069db5>] ?
trace_hardirqs_on+0xd/0xf
Nov 14 12:03:31 nehalam kernel: [ 5527.284735] [<ffffffffa0041c8e>]
btrfs_lookup+0x16/0x2e [btrfs]
Nov 14 12:03:31 nehalam kernel: [ 5527.284738] [<ffffffff810f97b5>]
d_alloc_and_lookup+0x55/0x74
Nov 14 12:03:31 nehalam kernel: [ 5527.284741] [<ffffffff810f98dc>]
do_lookup+0xbb/0x10d
Nov 14 12:03:31 nehalam kernel: [ 5527.284744] [<ffffffff810fb6a1>]
link_path_walk+0x2a6/0x3fc
Nov 14 12:03:31 nehalam kernel: [ 5527.284746] [<ffffffff810fb8f3>]
path_walk+0x69/0xd9
Nov 14 12:03:31 nehalam kernel: [ 5527.284750] [<ffffffff811e23c2>] ?
strncpy_from_user+0x48/0x76
Nov 14 12:03:31 nehalam kernel: [ 5527.284753] [<ffffffff810fba35>]
do_path_lookup+0x2a/0x4f
Nov 14 12:03:31 nehalam kernel: [ 5527.284756] [<ffffffff810fc52f>]
user_path_at+0x56/0x9a
Nov 14 12:03:31 nehalam kernel: [ 5527.284760] [<ffffffff810caa14>] ?
might_fault+0x5c/0xac
Nov 14 12:03:31 nehalam kernel: [ 5527.284764] [<ffffffff810f4701>] ?
cp_new_stat+0xf7/0x10d
Nov 14 12:03:31 nehalam kernel: [ 5527.284767] [<ffffffff810f45a2>]
vfs_fstatat+0x37/0x62
Nov 14 12:03:31 nehalam kernel: [ 5527.284770] [<ffffffff810f45eb>]
vfs_lstat+0x1e/0x20
Nov 14 12:03:31 nehalam kernel: [ 5527.284772] [<ffffffff810f4773>]
sys_newlstat+0x1f/0x3d
Nov 14 12:03:31 nehalam kernel: [ 5527.284776] [<ffffffff81069d84>] ?
trace_hardirqs_on_caller+0x118/0x13c
Nov 14 12:03:31 nehalam kernel: [ 5527.284779] [<ffffffff813b2fe0>] ?
trace_hardirqs_on_thunk+0x3a/0x3f
Nov 14 12:03:31 nehalam kernel: [ 5527.284783] [<ffffffff8100245b>]
system_call_fastpath+0x16/0x1b
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