dquot.c: possible circular locking Re: [2.6.20] BUG: workqueue leaked lock

From: Jarek Poplawski
Date: Tue Mar 20 2007 - 07:12:53 EST

On 15-03-2007 20:17, Folkert van Heusden wrote:
>>> On Tue, 13 Mar 2007 17:50:14 +0100 Folkert van Heusden <folkert@xxxxxxxxxxxxxx> wrote:
...
> Haha ok :-)
>
> Good, since I run 2.6.20 with these debugging switches switched on, I
> get occasionally errors like these. I get ALWAYS the following error
> when the system first boots when the TOR executable is started:
>
> [ 137.324255] =======================================================
> [ 137.324359] [ INFO: possible circular locking dependency detected ]
> [ 137.324412] 2.6.20 #2
> [ 137.324457] -------------------------------------------------------
> [ 137.324510] tor/4857 is trying to acquire lock:
> [ 137.324559] (tty_mutex){--..}, at: [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.324765]
> [ 137.324766] but task is already holding lock:
> [ 137.324859] (&s->s_dquot.dqptr_sem){----}, at: [<c1099403>] dquot_alloc_space+0x50/0x189
> [ 137.325067]
> [ 137.325069] which lock already depends on the new lock.

IMHO lockdep found that two locks are taken in different order:

-> #1: 1) tty_mutex in con_console() 2) dqptr_sem (somewhere later)
-> #0: 1) dqptr_sem 2) tty_console in dquot_alloc_space() with print_warning()

Probably print_warning() and flush_warnings() should be reworked
to do printing without dqptr_sem or locking order should be changed.
I hope somebody from this CC can work it out better.

Regards,
Jarek P.


> [ 137.325071]
> [ 137.325206]
> [ 137.325208] the existing dependency chain (in reverse order) is:
> [ 137.325300]
> [ 137.325301] -> #4 (&s->s_dquot.dqptr_sem){----}:
> [ 137.325501] [<c10354b8>] check_prev_add+0x154/0x206
> [ 137.325852] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.326197] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.326538] [<c1037624>] lock_acquire+0x62/0x81
> [ 137.326887] [<c1032b5f>] down_read+0x2b/0x3d
> [ 137.327241] [<c1099403>] dquot_alloc_space+0x50/0x189
> [ 137.327588] [<c10a98e6>] ext3_new_blocks+0x44b/0x5a2
> [ 137.327935] [<c10abe78>] ext3_alloc_blocks+0x40/0xdf
> [ 137.328280] [<c10abf67>] ext3_alloc_branch+0x50/0x21b
> [ 137.328622] [<c10ac445>] ext3_get_blocks_handle+0x1b8/0x367
> [ 137.328980] [<c10ac76e>] ext3_getblk+0x97/0x228
> [ 137.329330] [<c10ac919>] ext3_bread+0x1a/0x78
> [ 137.329672] [<c10b1bc2>] ext3_mkdir+0xf4/0x270
> [ 137.330022] [<c1072a6a>] vfs_mkdir+0xb3/0x161
> [ 137.330368] [<c1072ba4>] sys_mkdirat+0x8c/0xc4
> [ 137.330714] [<c1072bfc>] sys_mkdir+0x20/0x22
> [ 137.331063] [<c1002f78>] syscall_call+0x7/0xb
> [ 137.331406] [<ffffffff>] 0xffffffff
> [ 137.331771]
> [ 137.331772] -> #3 (&ei->truncate_mutex){--..}:
> [ 137.331979] [<c10354b8>] check_prev_add+0x154/0x206
> [ 137.332332] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.332676] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.333025] [<c1037624>] lock_acquire+0x62/0x81
> [ 137.333370] [<c1205c09>] __mutex_lock_slowpath+0x75/0x28c
> [ 137.333930] [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.334271] [<c10ae14f>] ext3_truncate+0x170/0x468
> [ 137.334613] [<c1058e72>] vmtruncate+0xa6/0x116
> [ 137.334949] [<c107d587>] inode_setattr+0x145/0x16c
> [ 137.335286] [<c10af071>] ext3_setattr+0x150/0x22f
> [ 137.335627] [<c107d909>] notify_change+0x35b/0x392
> [ 137.335968] [<c10679d2>] do_truncate+0x52/0x75
> [ 137.336305] [<c1071f5e>] may_open+0x1ec/0x231
> [ 137.336642] [<c107211c>] open_namei+0xda/0x59b
> [ 137.336975] [<c106863a>] do_filp_open+0x2c/0x53
> [ 137.337310] [<c106896f>] do_sys_open+0x52/0xd8
> [ 137.337645] [<c1068a11>] sys_open+0x1c/0x1e
> [ 137.337980] [<c1002f78>] syscall_call+0x7/0xb
> [ 137.338315] [<ffffffff>] 0xffffffff
> [ 137.338665]
> [ 137.338666] -> #2 (&inode->i_alloc_sem){--..}:
> [ 137.338864] [<c10354b8>] check_prev_add+0x154/0x206
> [ 137.339200] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.339535] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.339200] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.339535] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.339874] [<c1037624>] lock_acquire+0x62/0x81
> [ 137.340207] [<c1032bf5>] down_write+0x2b/0x45
> [ 137.340545] [<c107d890>] notify_change+0x2e2/0x392
> [ 137.340886] [<c10679d2>] do_truncate+0x52/0x75
> [ 137.341222] [<c1071f5e>] may_open+0x1ec/0x231
> [ 137.341557] [<c107211c>] open_namei+0xda/0x59b
> [ 137.341898] [<c1068a11>] sys_open+0x1c/0x1e
> [ 137.343109] [<c1002f78>] syscall_call+0x7/0xb
> [ 137.343444] [<ffffffff>] 0xffffffff
> [ 137.343792]
> [ 137.343793] -> #1 (&sysfs_inode_imutex_key){--..}:
> [ 137.343988] [<c10354b8>] check_prev_add+0x154/0x206
> [ 137.344320] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.344655] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.344986] [<c1037624>] lock_acquire+0x62/0x81
> [ 137.345321] [<c1205c09>] __mutex_lock_slowpath+0x75/0x28c
> [ 137.345658] [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.345991] [<c10a5447>] sysfs_hash_and_remove+0x43/0x11c
> [ 137.346328] [<c10a5ef7>] sysfs_remove_file+0xd/0x12
> [ 137.346660] [<c114b00c>] device_remove_file+0x32/0x44
> [ 137.346992] [<c114b6d9>] device_del+0x174/0x1d2
> [ 137.347325] [<c114b742>] device_unregister+0xb/0x15
> [ 137.347661] [<c114b93d>] device_destroy+0x8d/0x9a
> [ 137.347994] [<c1137a38>] vcs_remove_sysfs+0x1c/0x38
> [ 137.348328] [<c113e0d8>] con_close+0x5e/0x6b
> [ 137.348661] [<c1130103>] release_dev+0x4c4/0x6ce
> [ 137.348999] [<c113077b>] tty_release+0x12/0x1c
> [ 137.349332] [<c10aa723>] ext3_file_write+0x2d/0xba
> [ 137.358495] [<c1069441>] do_sync_write+0xc7/0x116
> [ 137.358838] [<c1069612>] vfs_write+0x182/0x187
> [ 137.359176] [<c10696b8>] sys_write+0x3d/0x64
> [ 137.359513] [<c1002f78>] syscall_call+0x7/0xb
> [ 137.359848] [<ffffffff>] 0xffffffff
> [ 137.360200]
> [ 137.360202] other info that might help us debug this:
> [ 137.360204]
> [ 137.360335] 3 locks held by tor/4857:
> [ 137.360382] #0: (&inode->i_mutex){--..}, at: [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.360625] #1: (&ei->truncate_mutex){--..}, at: [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.361072] #2: (&s->s_dquot.dqptr_sem){----}, at: [<c1099403>] dquot_alloc_space+0x50/0x189
> [ 137.361313]
> [ 137.361314] stack backtrace:
> [ 137.361401] [<c1003d57>] show_trace_log_lvl+0x1a/0x30
> [ 137.361488] [<c1003d7f>] show_trace+0x12/0x14
> [ 137.361571] [<c1003e79>] dump_stack+0x16/0x18
> [ 137.361663] [<c1034d6d>] print_circular_bug_tail+0x6f/0x71
> [ 137.361752] [<c1035398>] check_prev_add+0x34/0x206
> [ 137.361838] [<c10355d4>] check_prevs_add+0x6a/0xd5
> [ 137.362786] [<c1036dd2>] __lock_acquire+0x61c/0xa05
> [ 137.362877] [<c1037624>] lock_acquire+0x62/0x81
> [ 137.362960] [<c1205c09>] __mutex_lock_slowpath+0x75/0x28c
> [ 137.363047] [<c1205b88>] mutex_lock+0x8/0xa
> [ 137.363132] [<c1098d79>] print_warning+0x8c/0x15d
> [ 137.363217] [<c1099537>] dquot_alloc_space+0x184/0x189
> [ 137.363302] [<c10a98e6>] ext3_new_blocks+0x44b/0x5a2
> [ 137.363391] [<c10abe78>] ext3_alloc_blocks+0x40/0xdf
> [ 137.363476] [<c10abf67>] ext3_alloc_branch+0x50/0x21b
> [ 137.363561] [<c10ac445>] ext3_get_blocks_handle+0x1b8/0x367
> [ 137.363650] [<c10ac66c>] ext3_get_block+0x78/0xe3
> [ 137.363735] [<c108a239>] __block_prepare_write+0x168/0x3fd
> [ 137.363822] [<c108ad10>] block_prepare_write+0x28/0x3b
> [ 137.363908] [<c10acbcd>] ext3_prepare_write+0x3f/0x18d
> [ 137.363996] [<c104dbe5>] generic_file_buffered_write+0x197/0x5e6
> [ 137.364084] [<c104e2e2>] __generic_file_aio_write_nolock+0x2ae/0x5ad
> [ 137.364171] [<c104e6ea>] generic_file_aio_write+0x58/0xc4
> [ 137.364254] [<c10aa723>] ext3_file_write+0x2d/0xba
> [ 137.364340] [<c1069441>] do_sync_write+0xc7/0x116
> [ 137.364425] [<c1069612>] vfs_write+0x182/0x187
> [ 137.364511] [<c10696b8>] sys_write+0x3d/0x64
> [ 137.364595] [<c1002f78>] syscall_call+0x7/0xb
> [ 137.364682] =======================
>
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