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Bug #145
closed"INFO: possible circular locking dependency detected" on module unloading
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Description
When doing a rmmod off the batman-adv kernel module, the info about a possible circlular locking dependancy shows up (see below). Despite from that, the system is continuing to run normal, so no kernel freeze. Reproducable: always
kvm image: Linux mesh-node1 2.6.37 #3 SMP PREEMPT Mon Feb 7 07:53:08 GMT 2011 i686 GNU/Linux
(kernel has been compiled with extra kernel hacking debug stuff)
batman-adv: svn rev. 1945; also present in v2011.0.0
[ 104.055934] batman_adv: B.A.T.M.A.N. advanced devel (compatibility version 12) loaded
[ 104.406641] batman_adv: bat0: Adding interface: eth1
[ 104.414163] batman_adv: bat0: The MTU of interface eth1 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1527 would solve the problem.
[ 104.430237] batman_adv: bat0: Not using interface eth1 (retrying later): interface not active
[ 104.443770] batman_adv: bat0: Adding interface: eth2
[ 104.467688] batman_adv: bat0: The MTU of interface eth2 is too small (1500) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to 1527 would solve the problem.
[ 104.480623] batman_adv: bat0: Not using interface eth2 (retrying later): interface not active
[ 104.608414] eth1: link up, 100Mbps, full-duplex, lpa 0x05E1
[ 104.621756] batman_adv: bat0: Interface activated: eth1
[ 104.677809] eth2: link up, 100Mbps, full-duplex, lpa 0x05E1
[ 104.683625] batman_adv: bat0: Interface activated: eth2
[ 119.319279]
[ 119.319281] =======================================================
[ 119.320075] [ INFO: possible circular locking dependency detected ]
[ 119.320075] 2.6.37 #3
[ 119.320075] -------------------------------------------------------
[ 119.320075] rmmod/2977 is trying to acquire lock:
[ 119.320075] (s_active#58){++++.+}, at: [<c1146aef>] sysfs_remove_dir+0x5e/0x6c
[ 119.320075]
[ 119.320075] but task is already holding lock:
[ 119.320075] (rtnl_mutex){+.+.+.}, at: [<c1429703>] rtnl_lock+0xf/0x11
[ 119.320075]
[ 119.320075] which lock already depends on the new lock.
[ 119.320075]
[ 119.320075]
[ 119.320075] the existing dependency chain (in reverse order) is:
[ 119.320075]
[ 119.320075] -> #1 (rtnl_mutex){+.+.+.}:
[ 119.320075] [<c1087d68>] lock_acquire+0xce/0xeb
[ 119.320075] [<c154a9b3>] +mutex_lock_common+0x3e/0x3a6
[ 119.320075] [<c154adaa>] mutex_lock_nested+0x2b/0x33
[ 119.320075] [<c1429703>] rtnl_lock+0xf/0x11
[ 119.320075] [<c14200f5>] register_netdev+0xc/0x3f
[ 119.320075] [<f1d0dfff>] softif_create+0x38/0x137 [batman_adv]
[ 119.320075] [<f1d099eb>] hardif_enable_interface+0x4f/0x22a [batman_adv]
[ 119.320075] [<f1d07cc2>] store_mesh_iface+0xed/0x113 [batman_adv]
[ 119.320075] [<c11defd1>] kobj_attr_store+0x1a/0x22
[ 119.320075] [<c11457df>] sysfs_write_file+0xb9/0xe4
[ 119.320075] [<c10fcd50>] vfs_write+0x84/0xde
[ 119.320075] [<c10fce43>] sys_write+0x3b/0x60
[ 119.320075] [<c154c45d>] syscall_call+0x7/0xb
[ 119.320075]
[ 119.320075] -> #0 (s_active#58){++++.+}:
[ 119.320075] [<c1087a00>] +lock_acquire+0x966/0xc00
[ 119.320075] [<c1087d68>] lock_acquire+0xce/0xeb
[ 119.320075] [<c11469f3>] sysfs_addrm_finish+0x92/0xf9
[ 119.320075] [<c1146aef>] sysfs_remove_dir+0x5e/0x6c
[ 119.320075] [<c11df397>] kobject_del+0xf/0x2c
[ 119.320075] [<c11df3e6>] kobject_release+0x32/0x50
[ 119.320075] [<c11e0191>] kref_put+0x39/0x44
[ 119.320075] [<c11df330>] kobject_put+0x37/0x3c
[ 119.320075] [<f1d07689>] sysfs_del_hardif+0xd/0x16 [batman_adv]
[ 119.320075] [<f1d0969a>] hardif_remove_interface+0x23/0x3e [batman_adv]
[ 119.320075] [<f1d09989>] hardif_remove_interfaces+0x6d/0x80 [batman_adv]
[ 119.320075] [<f1d11825>] batman_exit+0x17/0x3c [batman_adv]
[ 119.320075] [<c109226e>] sys_delete_module+0x184/0x1dc
[ 119.320075] [<c154c45d>] syscall_call+0x7/0xb
[ 119.320075]
[ 119.320075] other info that might help us debug this:
[ 119.320075]
[ 119.320075] 1 lock held by rmmod/2977:
[ 119.320075] #0: (rtnl_mutex){+.+.+.}, at: [<c1429703>] rtnl_lock+0xf/0x11
[ 119.320075]
[ 119.320075] stack backtrace:
[ 119.320075] Pid: 2977, comm: rmmod Not tainted 2.6.37 #3
[ 119.320075] Call Trace:
[ 119.320075] [<c15496c7>] ? printk+0xf/0x11
[ 119.320075] [<c1086d5d>] print_circular_bug+0x90/0x9c
[ 119.320075] [<c1087a00>] +lock_acquire+0x966/0xc00
[ 119.320075] [<c1087d68>] lock_acquire+0xce/0xeb
[ 119.320075] [<c1146aef>] ? sysfs_remove_dir+0x5e/0x6c
[ 119.320075] [<c11469f3>] sysfs_addrm_finish+0x92/0xf9
[ 119.320075] [<c1146aef>] ? sysfs_remove_dir+0x5e/0x6c
[ 119.320075] [<c1146aef>] sysfs_remove_dir+0x5e/0x6c
[ 119.320075] [<c11df397>] kobject_del+0xf/0x2c
[ 119.320075] [<c11df3e6>] kobject_release+0x32/0x50
[ 119.320075] [<c11df3b4>] ? kobject_release+0x0/0x50
[ 119.320075] [<c11e0191>] kref_put+0x39/0x44
[ 119.320075] [<c11df330>] kobject_put+0x37/0x3c
[ 119.320075] [<f1d07689>] sysfs_del_hardif+0xd/0x16 [batman_adv]
[ 119.320075] [<f1d0969a>] hardif_remove_interface+0x23/0x3e [batman_adv]
[ 119.320075] [<f1d09989>] hardif_remove_interfaces+0x6d/0x80 [batman_adv]
[ 119.320075] [<f1d11825>] batman_exit+0x17/0x3c [batman_adv]
[ 119.320075] [<c109226e>] sys_delete_module+0x184/0x1dc
[ 119.320075] [<c1085771>] ? put_lock_stats+0xd/0x22
[ 119.320075] [<c108583b>] ? lock_release_holdtime+0xb5/0xba
[ 119.320075] [<c10e96ff>] ? sys_munmap+0x39/0x3f
[ 119.320075] [<c154c490>] ? restore_all_notrace+0x0/0x18
[ 119.320075] [<c154c45d>] syscall_call+0x7/0xb
[ 119.595625] batman_adv: bat0: Interface deactivated: eth1
[ 119.599457] batman_adv: bat0: Removing interface: eth1
[ 119.605511] batman_adv: bat0: Interface deactivated: eth2
[ 119.613108] batman_adv: bat0: Removing interface: eth2
[ 119.625336] netconsole: network logging stopped, interface bat0 unregistered
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