(cred_guard_mutex vs seq->lock) INFO: possible circular locking dependencydetected

From: Li Zefan
Date: Fri May 17 2013 - 05:04:14 EST

[ 130.287724] ======================================================
[ 130.287732] [ INFO: possible circular locking dependency detected ]
[ 130.287742] 3.10.0-rc1-0.7-default+ #9 Not tainted
[ 130.287749] -------------------------------------------------------
[ 130.287758] trinity-child3/11061 is trying to acquire lock:
[ 130.287766] (&p->lock){+.+.+.}, at: [<ffffffff811a3ed0>] seq_read+0x40/0x410
[ 130.287784]
[ 130.287784] but task is already holding lock:
[ 130.287794] (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff81183f77>] prepare_bprm_creds+0x37/0x80
[ 130.287812]
[ 130.287812] which lock already depends on the new lock.
[ 130.287812]
[ 130.287826]
[ 130.287826] the existing dependency chain (in reverse order) is:
[ 130.287837]
[ 130.287837] -> #1 (&sig->cred_guard_mutex){+.+.+.}:
[ 130.287851] [<ffffffff810aa49c>] lock_acquire+0xdc/0x110
[ 130.287862] [<ffffffff814994cc>] mutex_lock_killable_nested+0x4c/0x420
[ 130.287876] [<ffffffff8103cd24>] mm_access+0x34/0xc0
[ 130.287886] [<ffffffff811e5d71>] m_start+0x71/0x180
[ 130.287897] [<ffffffff811a3f2b>] seq_read+0x9b/0x410
[ 130.287907] [<ffffffff8117d558>] vfs_read+0xc8/0x130
[ 130.287919] [<ffffffff8117dbf4>] SyS_read+0x64/0xa0
[ 130.287929] [<ffffffff814a6682>] system_call_fastpath+0x16/0x1b
[ 130.287941]
[ 130.287941] -> #0 (&p->lock){+.+.+.}:
[ 130.287953] [<ffffffff810a9ffd>] __lock_acquire+0x14dd/0x18a0
[ 130.287963] [<ffffffff810aa49c>] lock_acquire+0xdc/0x110
[ 130.287973] [<ffffffff81498d20>] mutex_lock_nested+0x40/0x390
[ 130.287984] [<ffffffff811a3ed0>] seq_read+0x40/0x410
[ 130.287993] [<ffffffff811e6f1f>] proc_reg_read+0x4f/0x80
[ 130.288004] [<ffffffff8117d558>] vfs_read+0xc8/0x130
[ 130.288013] [<ffffffff81184369>] kernel_read+0x49/0x60
[ 130.288023] [<ffffffff8118446a>] prepare_binprm+0xea/0x180
[ 130.288033] [<ffffffff811850bb>] do_execve_common+0x48b/0x6e0
[ 130.288044] [<ffffffff811853d9>] do_execve+0x39/0x40
[ 130.288054] [<ffffffff81185427>] SyS_execve+0x47/0x70
[ 130.288063] [<ffffffff814a6c79>] stub_execve+0x69/0xa0
[ 130.288074]
[ 130.288074] other info that might help us debug this:
[ 130.288074]
[ 130.288088] Possible unsafe locking scenario:
[ 130.288088]
[ 130.288098] CPU0 CPU1
[ 130.288105] ---- ----
[ 130.288111] lock(&sig->cred_guard_mutex);
[ 130.288120] lock(&p->lock);
[ 130.288130] lock(&sig->cred_guard_mutex);
[ 130.288140] lock(&p->lock);
[ 130.288147]
[ 130.288147] *** DEADLOCK ***
[ 130.288147]
[ 130.288160] 1 lock held by trinity-child3/11061:
[ 130.288167] #0: (&sig->cred_guard_mutex){+.+.+.}, at: [<ffffffff81183f77>] prepare_bprm_creds+0x37/0x80
[ 130.288184]
[ 130.288184] stack backtrace:
[ 130.288195] CPU: 3 PID: 11061 Comm: trinity-child3 Not tainted 3.10.0-rc1-0.7-default+ #9
[ 130.288205] Hardware name: Huawei Technologies Co., Ltd. Tecal RH2285 /BC11BTSA , BIOS CTSAV036 04/27/2011
[ 130.288217] ffffffff81e51fa0 ffff880bf6cb5b18 ffffffff8149845c ffff880bf6cb5b58
[ 130.288231] ffffffff810a7183 0000000000000001 0000000000000000 0000000000000001
[ 130.288244] 0000000000000000 ffff880bf8be2680 00000000002e2188 ffff880bf6cb5c38
[ 130.288257] Call Trace:
[ 130.288266] [<ffffffff8149845c>] dump_stack+0x19/0x1d
[ 130.288276] [<ffffffff810a7183>] print_circular_bug+0x223/0x330
[ 130.288286] [<ffffffff810a9ffd>] __lock_acquire+0x14dd/0x18a0
[ 130.288296] [<ffffffff810aa49c>] lock_acquire+0xdc/0x110
[ 130.288306] [<ffffffff811a3ed0>] ? seq_read+0x40/0x410
[ 130.288317] [<ffffffff81498d20>] mutex_lock_nested+0x40/0x390
[ 130.288327] [<ffffffff811a3ed0>] ? seq_read+0x40/0x410
[ 130.288337] [<ffffffff811a3ed0>] seq_read+0x40/0x410
[ 130.288347] [<ffffffff8149d3fb>] ? _raw_spin_unlock+0x2b/0x40
[ 130.288360] [<ffffffff811971cf>] ? dput+0x9f/0x230
[ 130.288369] [<ffffffff811e6f1f>] proc_reg_read+0x4f/0x80
[ 130.288380] [<ffffffff8117d558>] vfs_read+0xc8/0x130
[ 130.288389] [<ffffffff81184369>] kernel_read+0x49/0x60
[ 130.288399] [<ffffffff8118446a>] prepare_binprm+0xea/0x180
[ 130.288409] [<ffffffff811850bb>] do_execve_common+0x48b/0x6e0
[ 130.288419] [<ffffffff81184d4f>] ? do_execve_common+0x11f/0x6e0
[ 130.288430] [<ffffffff811853d9>] do_execve+0x39/0x40
[ 130.288440] [<ffffffff81185427>] SyS_execve+0x47/0x70
[ 130.288450] [<ffffffff814a6c79>] stub_execve+0x69/0xa0
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