Adding to my previous mail, this fix is not enough. As you can see
below, it is never safe to call flush_scheduled_work() under rtnl
because some other things running *from* the global events workqueue
acquire the rtnl and hence it we could deadlock against them.
I think the fix would be to use cancel_delayed_work_sync() here instead
of a combination of cancel_delayed_work() and flush_workqueue().
[ 130.612315] =======================================================
[ 130.612331] [ INFO: possible circular locking dependency detected ]
[ 130.612338] 2.6.23-rc1-g05ff0970-dirty #244
[ 130.612343] -------------------------------------------------------
[ 130.612350] iwconfig/4443 is trying to acquire lock:
[ 130.612356] (events){--..}, at: [<c00000000006170c>] .flush_workqueue+0x44/0xf0
[ 130.612384]
[ 130.612385] but task is already holding lock:
[ 130.612391] (rtnl_mutex){--..}, at: [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 130.612414]
[ 130.612415] which lock already depends on the new lock.
[ 130.612418]
[ 130.612423]
[ 130.612424] the existing dependency chain (in reverse order) is:
[ 130.612430]
[ 130.612432] -> #2 (rtnl_mutex){--..}:
[ 130.612445] [<c000000000073e58>] .__lock_acquire+0xce8/0xf20
[ 130.612472] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 130.612498] [<c0000000003b96cc>] .__mutex_lock_slowpath+0x138/0x3f0
[ 130.612526] [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 130.612553] [<c00000000033b85c>] .rtnl_lock+0x28/0x44
[ 130.612582] [<c00000000033d8ac>] .linkwatch_event+0x20/0x6c
[ 130.612609] [<c000000000060720>] .run_workqueue+0x16c/0x290
[ 130.612636] [<c000000000061d2c>] .worker_thread+0x13c/0x16c
[ 130.612664] [<c000000000066b98>] .kthread+0x84/0xd4
[ 130.612690] [<c000000000022734>] .kernel_thread+0x4c/0x68
[ 130.612721]
[ 130.612723] -> #1 ((linkwatch_work).work){--..}:
[ 130.612737] [<c000000000073e58>] .__lock_acquire+0xce8/0xf20
[ 130.612774] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 130.612801] [<c000000000060700>] .run_workqueue+0x14c/0x290
[ 130.612821] [<c000000000061d2c>] .worker_thread+0x13c/0x16c
[ 130.612886] [<c000000000066b98>] .kthread+0x84/0xd4
[ 130.612961] [<c000000000022734>] .kernel_thread+0x4c/0x68
[ 130.613038]
[ 130.613040] -> #0 (events){--..}:
[ 130.613074] [<c000000000073d50>] .__lock_acquire+0xbe0/0xf20
[ 130.613149] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 130.613224] [<c00000000006173c>] .flush_workqueue+0x74/0xf0
[ 130.613303] [<c0000000000617e0>] .flush_scheduled_work+0x28/0x40
[ 130.613377] [<d0000000004c8dd4>] .ieee80211softmac_wx_set_essid+0x168/0x234 [ieee80211softmac]
[ 130.613473] [<c0000000003b5a8c>] .ioctl_standard_call+0x298/0x3bc
[ 130.613553] [<c0000000003b5d38>] .wext_handle_ioctl+0x188/0x4b4
[ 130.613625] [<c000000000330d54>] .dev_ioctl+0x584/0x5e0
[ 130.613697] [<c000000000320514>] .sock_ioctl+0x2fc/0x33c
[ 130.613751] [<c0000000000d9568>] .do_ioctl+0x5c/0xf8
[ 130.613827] [<c0000000000d9a5c>] .vfs_ioctl+0x458/0x490
[ 130.613905] [<c0000000000d9af0>] .sys_ioctl+0x5c/0xa4
[ 130.613982] [<c000000000110d88>] .do_wireless_ioctl+0x1d0/0x224
[ 130.614059] [<c00000000010c5ec>] .compat_sys_ioctl+0x3e0/0x470
[ 130.614137] [<c0000000000086d0>] syscall_exit+0x0/0x40
[ 130.614217]
[ 130.614219] other info that might help us debug this:
[ 130.614221]
[ 130.614232] 1 lock held by iwconfig/4443:
[ 130.614242] #0: (rtnl_mutex){--..}, at: [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 130.614295]
[ 130.614297] stack backtrace:
[ 130.614307] Call Trace:
[ 130.614318] [c00000010c58f0e0] [c00000000000f2e4] .show_stack+0x78/0x1a4 (unreliable)
[ 130.614358] [c00000010c58f190] [c00000000000f430] .dump_stack+0x20/0x34
[ 130.614388] [c00000010c58f210] [c00000000007141c] .print_circular_bug_tail+0x88/0xac
[ 130.614421] [c00000010c58f2e0] [c000000000073d50] .__lock_acquire+0xbe0/0xf20
[ 130.614450] [c00000010c58f3d0] [c000000000074160] .lock_acquire+0xd0/0x11c
[ 130.614478] [c00000010c58f490] [c00000000006173c] .flush_workqueue+0x74/0xf0
[ 130.614505] [c00000010c58f530] [c0000000000617e0] .flush_scheduled_work+0x28/0x40
[ 130.614533] [c00000010c58f5b0] [d0000000004c8dd4] .ieee80211softmac_wx_set_essid+0x168/0x234 [ieee80211softmac]
[ 130.614573] [c00000010c58f680] [c0000000003b5a8c] .ioctl_standard_call+0x298/0x3bc
[ 130.614606] [c00000010c58f790] [c0000000003b5d38] .wext_handle_ioctl+0x188/0x4b4
[ 130.614640] [c00000010c58f870] [c000000000330d54] .dev_ioctl+0x584/0x5e0
[ 130.614669] [c00000010c58f990] [c000000000320514] .sock_ioctl+0x2fc/0x33c
[ 130.614695] [c00000010c58fa40] [c0000000000d9568] .do_ioctl+0x5c/0xf8
[ 130.614722] [c00000010c58fae0] [c0000000000d9a5c] .vfs_ioctl+0x458/0x490
[ 130.614752] [c00000010c58fb90] [c0000000000d9af0] .sys_ioctl+0x5c/0xa4
[ 130.614782] [c00000010c58fc50] [c000000000110d88] .do_wireless_ioctl+0x1d0/0x224
[ 130.614811] [c00000010c58fd30] [c00000000010c5ec] .compat_sys_ioctl+0x3e0/0x470
[ 130.614840] [c00000010c58fe30] [c0000000000086d0] syscall_exit+0x0/0x40
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