linux-kernel - Re: 2.6.28-rc2-mm1: possible circular locking

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Date:	Wed, 29 Oct 2008 21:46:03 +0100
From:	Mariusz Kozlowski <m.kozlowski@...land.pl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, kernel-testers@...r.kernel.org
Subject: Re: 2.6.28-rc2-mm1: possible circular locking

Hello,

	Happens on every startup when psi starts as well.

=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.28-rc2-mm1 #1
-------------------------------------------------------
psi/4733 is trying to acquire lock:
 (events){--..}, at: [<c012a330>] flush_work+0x2d/0xcb

but task is already holding lock:
 (&mm->mmap_sem){----}, at: [<c0158588>] sys_mlock+0x2c/0xb6

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #4 (&mm->mmap_sem){----}:
       [<c013ac05>] validate_chain+0xacb/0xfe0
       [<c013b388>] __lock_acquire+0x26e/0x98d
       [<c013bb03>] lock_acquire+0x5c/0x74
       [<c015728a>] might_fault+0x74/0x90
       [<c01e5cf8>] copy_to_user+0x28/0x40
       [<c01768aa>] filldir64+0xaa/0xcd
       [<c01a46d9>] sysfs_readdir+0x118/0x1dd
       [<c01769fb>] vfs_readdir+0x70/0x85
       [<c0176a70>] sys_getdents64+0x60/0xa8
       [<c0102f91>] sysenter_do_call+0x12/0x35
       [<ffffffff>] 0xffffffff

-> #3 (sysfs_mutex){--..}:
       [<c013ac05>] validate_chain+0xacb/0xfe0
       [<c013b388>] __lock_acquire+0x26e/0x98d
       [<c013bb03>] lock_acquire+0x5c/0x74
       [<c02bc360>] mutex_lock_nested+0x8d/0x297
       [<c01a495a>] sysfs_addrm_start+0x26/0x9e
       [<c01a4e25>] create_dir+0x3a/0x83
       [<c01a4e99>] sysfs_create_dir+0x2b/0x43
       [<c01e09a0>] kobject_add_internal+0xb4/0x186
       [<c01e0b2f>] kobject_add_varg+0x41/0x4d
       [<c01e0dbc>] kobject_add+0x2f/0x57
       [<c023d074>] device_add+0xa4/0x58f
       [<c0276a53>] netdev_register_kobject+0x65/0x6a
       [<c026bed0>] register_netdevice+0x209/0x2fb
       [<c026bff4>] register_netdev+0x32/0x3f
       [<c03c4344>] loopback_net_init+0x33/0x6f
       [<c02690ff>] register_pernet_operations+0x13/0x15
       [<c026916a>] register_pernet_device+0x1f/0x4c
       [<c03c430f>] loopback_init+0xd/0xf
       [<c0101027>] _stext+0x27/0x147
       [<c03ac7af>] kernel_init+0x7d/0xd6
       [<c0103cc3>] kernel_thread_helper+0x7/0x14
       [<ffffffff>] 0xffffffff

-> #2 (rtnl_mutex){--..}:
       [<c013ac05>] validate_chain+0xacb/0xfe0
       [<c013b388>] __lock_acquire+0x26e/0x98d
       [<c013bb03>] lock_acquire+0x5c/0x74
       [<c02bc360>] mutex_lock_nested+0x8d/0x297
       [<c02746d3>] rtnl_lock+0xf/0x11
       [<c0275ab3>] linkwatch_event+0x8/0x27
       [<c0129d40>] run_workqueue+0x15c/0x1e3
       [<c012a70e>] worker_thread+0x71/0xa4
       [<c012cc62>] kthread+0x37/0x59
       [<c0103cc3>] kernel_thread_helper+0x7/0x14
       [<ffffffff>] 0xffffffff

-> #1 ((linkwatch_work).work){--..}:
       [<c013ac05>] validate_chain+0xacb/0xfe0
       [<c013b388>] __lock_acquire+0x26e/0x98d
       [<c013bb03>] lock_acquire+0x5c/0x74
       [<c0129d3b>] run_workqueue+0x157/0x1e3
       [<c012a70e>] worker_thread+0x71/0xa4
       [<c012cc62>] kthread+0x37/0x59
       [<c0103cc3>] kernel_thread_helper+0x7/0x14
       [<ffffffff>] 0xffffffff

-> #0 (events){--..}:
       [<c013a6e4>] validate_chain+0x5aa/0xfe0
       [<c013b388>] __lock_acquire+0x26e/0x98d
       [<c013bb03>] lock_acquire+0x5c/0x74
       [<c012a35c>] flush_work+0x59/0xcb
       [<c012a7a6>] schedule_on_each_cpu+0x65/0x7f
       [<c014fb7e>] lru_add_drain_all+0xd/0xf
       [<c0157fb2>] __mlock_vma_pages_range+0x44/0x206
       [<c01582d1>] mlock_fixup+0x15d/0x1c9
       [<c0158479>] do_mlock+0x96/0xc8
       [<c015860e>] sys_mlock+0xb2/0xb6
       [<c0102f91>] sysenter_do_call+0x12/0x35
       [<ffffffff>] 0xffffffff

other info that might help us debug this:

1 lock held by psi/4733:
 #0:  (&mm->mmap_sem){----}, at: [<c0158588>] sys_mlock+0x2c/0xb6

stack backtrace:
Pid: 4733, comm: psi Not tainted 2.6.28-rc2-mm1 #1
Call Trace:
 [<c013a0fd>] print_circular_bug_tail+0x78/0xb5
 [<c0137a31>] ? print_circular_bug_entry+0x43/0x4b
 [<c013a6e4>] validate_chain+0x5aa/0xfe0
 [<c0118465>] ? hrtick_update+0x23/0x25
 [<c013b388>] __lock_acquire+0x26e/0x98d
 [<c0118ac0>] ? default_wake_function+0xb/0xd
 [<c013bb03>] lock_acquire+0x5c/0x74
 [<c012a330>] ? flush_work+0x2d/0xcb
 [<c012a35c>] flush_work+0x59/0xcb
 [<c012a330>] ? flush_work+0x2d/0xcb
 [<c0139ae6>] ? trace_hardirqs_on+0xb/0xd
 [<c012a531>] ? __queue_work+0x26/0x2b
 [<c012a58c>] ? queue_work_on+0x37/0x47
 [<c014fda7>] ? lru_add_drain_per_cpu+0x0/0xa
 [<c014fda7>] ? lru_add_drain_per_cpu+0x0/0xa
 [<c012a7a6>] schedule_on_each_cpu+0x65/0x7f
 [<c014fb7e>] lru_add_drain_all+0xd/0xf
 [<c0157fb2>] __mlock_vma_pages_range+0x44/0x206
 [<c0159438>] ? vma_adjust+0x17e/0x384
 [<c015971f>] ? split_vma+0xe1/0xf7
 [<c01582d1>] mlock_fixup+0x15d/0x1c9
 [<c0158479>] do_mlock+0x96/0xc8
 [<c02bcb2a>] ? down_write+0x42/0x68
 [<c015860e>] sys_mlock+0xb2/0xb6
 [<c0102f91>] sysenter_do_call+0x12/0x35

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