here's another one found on another box:
[ 574.380319] =======================================================
[ 574.380381] [ INFO: possible circular locking dependency detected ]
[ 574.380413] 2.6.27-rc6-tip #30918
[ 574.380440] -------------------------------------------------------
[ 574.380472] sshd/8255 is trying to acquire lock:
[ 574.380500] (&sb->s_type->i_mutex_key#9){--..}, at: [<ffffffff802d5aab>] do_truncate+0x59/0x83
[ 574.380628]
[ 574.380629] but task is already holding lock:
[ 574.380679] (&mm->mmap_sem){----}, at: [<ffffffff80249775>] sys32_mmap2+0x64/0xa7
[ 574.380781]
[ 574.380781] which lock already depends on the new lock.
[ 574.380782]
[ 574.380857]
[ 574.380857] the existing dependency chain (in reverse order) is:
[ 574.380910]
[ 574.380911] -> #1 (&mm->mmap_sem){----}:
[ 574.381025] [<ffffffff80281979>] __lock_acquire+0x9b4/0xb3b
[ 574.381081] [<ffffffff80282499>] lock_acquire+0x8d/0xba
[ 574.381219] [<ffffffff802a94ff>] iov_iter_fault_in_readable+0x84/0x169
[ 574.381359] [<ffffffff802aae18>] generic_file_buffered_write+0x119/0x5ad
[ 574.381584] [<ffffffff802ab6cb>] __generic_file_aio_write_nolock+0x260/0x294
[ 574.381809] [<ffffffff802ab768>] generic_file_aio_write+0x69/0xc5
[ 574.381948] [<ffffffff802d68e2>] do_sync_write+0xeb/0x132
[ 574.382086] [<ffffffff802d6f28>] vfs_write+0xa7/0xe1
[ 574.382222] [<ffffffff802d701c>] sys_write+0x47/0x6d
[ 574.382359] [<ffffffff802481b7>] cstar_dispatch+0x7/0x4b
[ 574.382496] [<ffffffffffffffff>] 0xffffffffffffffff
[ 574.382635]
[ 574.382636] -> #0 (&sb->s_type->i_mutex_key#9){--..}:
[ 574.382942] [<ffffffff8028181b>] __lock_acquire+0x856/0xb3b
[ 574.383080] [<ffffffff80282499>] lock_acquire+0x8d/0xba
[ 574.383218] [<ffffffff80b77600>] __mutex_lock_common+0xe4/0x333
[ 574.383358] [<ffffffff80b778e9>] mutex_lock_nested+0x30/0x35
[ 574.383495] [<ffffffff802d5aab>] do_truncate+0x59/0x83
[ 574.383633] [<ffffffff802cbbf7>] shmem_file_setup+0xcf/0x106
[ 574.383772] [<ffffffff802cbc50>] shmem_zero_setup+0x22/0x5e
[ 574.383910] [<ffffffff802bfc92>] mmap_region+0x250/0x438
[ 574.384031] [<ffffffff802c047f>] do_mmap_pgoff+0x2fe/0x363
[ 574.384031] [<ffffffff8024978e>] sys32_mmap2+0x7d/0xa7
[ 574.384031] [<ffffffff802481b7>] cstar_dispatch+0x7/0x4b
[ 574.384031] [<ffffffffffffffff>] 0xffffffffffffffff
[ 574.384031]
[ 574.384031] other info that might help us debug this:
[ 574.384031]
[ 574.384031] 1 lock held by sshd/8255:
[ 574.384031] #0: (&mm->mmap_sem){----}, at: [<ffffffff80249775>] sys32_mmap2+0x64/0xa7
[ 574.384031]
[ 574.384031] stack backtrace:
[ 574.384031] Pid: 8255, comm: sshd Not tainted 2.6.27-rc6-tip #30918
[ 574.384031] Call Trace:
[ 574.384031] [<ffffffff80280fba>] print_circular_bug_tail+0x71/0x7c
[ 574.384031] [<ffffffff8028181b>] __lock_acquire+0x856/0xb3b
[ 574.384031] [<ffffffff80282499>] lock_acquire+0x8d/0xba
[ 574.384031] [<ffffffff802d5aab>] ? do_truncate+0x59/0x83
[ 574.384031] [<ffffffff80b77600>] __mutex_lock_common+0xe4/0x333
[ 574.384031] [<ffffffff802d5aab>] ? do_truncate+0x59/0x83
[ 574.384031] [<ffffffff802d5aab>] ? do_truncate+0x59/0x83
[ 574.384031] [<ffffffff804e475f>] ? _raw_spin_unlock+0x8e/0x93
[ 574.384031] [<ffffffff80b778e9>] mutex_lock_nested+0x30/0x35
[ 574.384031] [<ffffffff802d5aab>] do_truncate+0x59/0x83
[ 574.384031] [<ffffffff802d7c1f>] ? init_file+0x99/0xbb
[ 574.384031] [<ffffffff802d7deb>] ? alloc_file+0x3e/0x4e
[ 574.384031] [<ffffffff802cbbf7>] shmem_file_setup+0xcf/0x106
[ 574.384031] [<ffffffff802cbc50>] shmem_zero_setup+0x22/0x5e
[ 574.384031] [<ffffffff802bfc92>] mmap_region+0x250/0x438
[ 574.384031] [<ffffffff802282aa>] ? arch_get_unmapped_area_topdown+0x192/0x294
[ 574.384031] [<ffffffff802c047f>] do_mmap_pgoff+0x2fe/0x363
[ 574.384031] [<ffffffff8024978e>] sys32_mmap2+0x7d/0xa7
[ 574.384031] [<ffffffff802481b7>] cstar_dispatch+0x7/0x4b
Ingo
--
