FYI, my workqueue lockdep patches (in -mm as workqueue-something) say
this about it:
[ 361.440737] =======================================================
[ 361.440753] [ INFO: possible circular locking dependency detected ]
[ 361.440761] 2.6.23-rc1-g05ff0970-dirty #244
[ 361.440766] -------------------------------------------------------
[ 361.440773] iwconfig/5551 is trying to acquire lock:
[ 361.440778] (events){--..}, at: [<c00000000006170c>] .flush_workqueue+0x44/0xf0
[ 361.440807]
[ 361.440808] but task is already holding lock:
[ 361.440814] (&softmac->associnfo.mutex){--..}, at: [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 361.440837]
[ 361.440839] which lock already depends on the new lock.
[ 361.440841]
[ 361.440847]
[ 361.440848] the existing dependency chain (in reverse order) is:
[ 361.440854]
[ 361.440856] -> #3 (&softmac->associnfo.mutex){--..}:
[ 361.440869] [<c000000000073e58>] .__lock_acquire+0xce8/0xf20
[ 361.440896] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 361.440922] [<c0000000003b96cc>] .__mutex_lock_slowpath+0x138/0x3f0
[ 361.440950] [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 361.440977] [<d0000000004c3cb4>] .ieee80211softmac_wx_set_essid+0x48/0x204 [ieee80211softmac]
[ 361.441019] [<c0000000003b5a8c>] .ioctl_standard_call+0x298/0x3bc
[ 361.441047] [<c0000000003b5d38>] .wext_handle_ioctl+0x188/0x4b4
[ 361.441074] [<c000000000330d54>] .dev_ioctl+0x584/0x5e0
[ 361.441102] [<c000000000320514>] .sock_ioctl+0x2fc/0x33c
[ 361.441130] [<c0000000000d9568>] .do_ioctl+0x5c/0xf8
[ 361.441159] [<c0000000000d9a5c>] .vfs_ioctl+0x458/0x490
[ 361.441186] [<c0000000000d9af0>] .sys_ioctl+0x5c/0xa4
[ 361.441212] [<c000000000110d88>] .do_wireless_ioctl+0x1d0/0x224
[ 361.441241] [<c00000000010c5ec>] .compat_sys_ioctl+0x3e0/0x470
[ 361.441268] [<c0000000000086d0>] syscall_exit+0x0/0x40
[ 361.441296]
[ 361.441298] -> #2 (rtnl_mutex){--..}:
[ 361.441311] [<c000000000073e58>] .__lock_acquire+0xce8/0xf20
[ 361.441337] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 361.441363] [<c0000000003b96cc>] .__mutex_lock_slowpath+0x138/0x3f0
[ 361.441392] [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 361.441419] [<c00000000033b85c>] .rtnl_lock+0x28/0x44
[ 361.441446] [<c00000000033d8ac>] .linkwatch_event+0x20/0x6c
[ 361.441474] [<c000000000060720>] .run_workqueue+0x16c/0x290
[ 361.441501] [<c000000000061d2c>] .worker_thread+0x13c/0x16c
[ 361.441528] [<c000000000066b98>] .kthread+0x84/0xd4
[ 361.441554] [<c000000000022734>] .kernel_thread+0x4c/0x68
[ 361.441582]
[ 361.441584] -> #1 ((linkwatch_work).work){--..}:
[ 361.441597] [<c000000000073e58>] .__lock_acquire+0xce8/0xf20
[ 361.441623] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 361.441648] [<c000000000060700>] .run_workqueue+0x14c/0x290
[ 361.441675] [<c000000000061d2c>] .worker_thread+0x13c/0x16c
[ 361.441702] [<c000000000066b98>] .kthread+0x84/0xd4
[ 361.441727] [<c000000000022734>] .kernel_thread+0x4c/0x68
[ 361.441755]
[ 361.441756] -> #0 (events){--..}:
[ 361.441769] [<c000000000073d50>] .__lock_acquire+0xbe0/0xf20
[ 361.441795] [<c000000000074160>] .lock_acquire+0xd0/0x11c
[ 361.441821] [<c00000000006173c>] .flush_workqueue+0x74/0xf0
[ 361.441859] [<c0000000000617e0>] .flush_scheduled_work+0x28/0x40
[ 361.441888] [<d0000000004c3dac>] .ieee80211softmac_wx_set_essid+0x140/0x204 [ieee80211softmac]
[ 361.441924] [<c0000000003b5a8c>] .ioctl_standard_call+0x298/0x3bc
[ 361.442017] [<c0000000003b5d38>] .wext_handle_ioctl+0x188/0x4b4
[ 361.442104] [<c000000000330d54>] .dev_ioctl+0x584/0x5e0
[ 361.442189] [<c000000000320514>] .sock_ioctl+0x2fc/0x33c
[ 361.442260] [<c0000000000d9568>] .do_ioctl+0x5c/0xf8
[ 361.442341] [<c0000000000d9a5c>] .vfs_ioctl+0x458/0x490
[ 361.442416] [<c0000000000d9af0>] .sys_ioctl+0x5c/0xa4
[ 361.442495] [<c000000000110d88>] .do_wireless_ioctl+0x1d0/0x224
[ 361.442577] [<c00000000010c5ec>] .compat_sys_ioctl+0x3e0/0x470
[ 361.442654] [<c0000000000086d0>] syscall_exit+0x0/0x40
[ 361.442737]
[ 361.442739] other info that might help us debug this:
[ 361.442742]
[ 361.442752] 2 locks held by iwconfig/5551:
[ 361.442763] #0: (rtnl_mutex){--..}, at: [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 361.442818] #1: (&softmac->associnfo.mutex){--..}, at: [<c0000000003b99c0>] .mutex_lock+0x3c/0x58
[ 361.442843]
[ 361.442845] stack backtrace:
[ 361.442850] Call Trace:
[ 361.442855] [c000000078eab100] [c00000000000f2e4] .show_stack+0x78/0x1a4 (unreliable)
[ 361.442887] [c000000078eab1b0] [c00000000000f430] .dump_stack+0x20/0x34
[ 361.442917] [c000000078eab230] [c00000000007141c] .print_circular_bug_tail+0x88/0xac
[ 361.442953] [c000000078eab300] [c000000000073d50] .__lock_acquire+0xbe0/0xf20
[ 361.442981] [c000000078eab3f0] [c000000000074160] .lock_acquire+0xd0/0x11c
[ 361.443009] [c000000078eab4b0] [c00000000006173c] .flush_workqueue+0x74/0xf0
[ 361.443039] [c000000078eab550] [c0000000000617e0] .flush_scheduled_work+0x28/0x40
[ 361.443073] [c000000078eab5d0] [d0000000004c3dac] .ieee80211softmac_wx_set_essid+0x140/0x204 [ieee80211softmac]
[ 361.443109] [c000000078eab680] [c0000000003b5a8c] .ioctl_standard_call+0x298/0x3bc
[ 361.443139] [c000000078eab790] [c0000000003b5d38] .wext_handle_ioctl+0x188/0x4b4
[ 361.443172] [c000000078eab870] [c000000000330d54] .dev_ioctl+0x584/0x5e0
[ 361.443203] [c000000078eab990] [c000000000320514] .sock_ioctl+0x2fc/0x33c
[ 361.443232] [c000000078eaba40] [c0000000000d9568] .do_ioctl+0x5c/0xf8
[ 361.443265] [c000000078eabae0] [c0000000000d9a5c] .vfs_ioctl+0x458/0x490
[ 361.443296] [c000000078eabb90] [c0000000000d9af0] .sys_ioctl+0x5c/0xa4
[ 361.443330] [c000000078eabc50] [c000000000110d88] .do_wireless_ioctl+0x1d0/0x224
[ 361.443363] [c000000078eabd30] [c00000000010c5ec] .compat_sys_ioctl+0x3e0/0x470
[ 361.443396] [c000000078eabe30] [c0000000000086d0] syscall_exit+0x0/0x40
We really need to get lockdep ported to ppc32...
johannes
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