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Date: Sun, 24 Feb 2013 11:31:47 -0600
From: Larry Finger <Larry.Finger@...inger.net>
To: Rafał Miłecki <zajec5@...il.com>,
Michael Büsch <m@...s.ch>
CC: linux-wireless <linux-wireless@...r.kernel.org>,
b43-dev <b43-dev@...ts.infradead.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Lockdep splat when unloading b43
With the current wireless-testing tree, unloading b43 produces the lockdep log
splat copied below. My understanding of locking is deficient, and I would like
to learn. Any help on understanding this problem is appreciated.
Larry
[ 3093.900871] ======================================================
[ 3093.900873] [ INFO: possible circular locking dependency detected ]
[ 3093.900876] 3.8.0-wl+ #117 Not tainted
[ 3093.900878] -------------------------------------------------------
[ 3093.900880] modprobe/5557 is trying to acquire lock:
[ 3093.900883] ((&wl->firmware_load)){+.+.+.}, at: [<ffffffff81062160>]
flush_work+0x0/0x2a0
[ 3093.900895]
[ 3093.900895] but task is already holding lock:
[ 3093.900897] (rtnl_mutex){+.+.+.}, at: [<ffffffff813bd7d2>] rtnl_lock+0x12/0x20
[ 3093.900905]
[ 3093.900905] which lock already depends on the new lock.
[ 3093.900905]
[ 3093.900908]
[ 3093.900908] the existing dependency chain (in reverse order) is:
[ 3093.900911]
[ 3093.900911] -> #1 (rtnl_mutex){+.+.+.}:
[ 3093.900915] [<ffffffff810a4bf6>] lock_acquire+0xa6/0x1e0
[ 3093.900922] [<ffffffff81458769>] mutex_lock_nested+0x69/0x370
[ 3093.900927] [<ffffffff813bd7d2>] rtnl_lock+0x12/0x20
[ 3093.900931] [<ffffffffa03e613c>] wiphy_register+0x59c/0x6c0 [cfg80211]
[ 3093.900965] [<ffffffffa050556b>] ieee80211_register_hw+0x37b/0x820
[mac80211]
[ 3093.901000] [<ffffffffa047a0bc>] b43_request_firmware+0x8c/0x180 [b43]
[ 3093.901014] [<ffffffff81063d0d>] process_one_work+0x19d/0x6f0
[ 3093.901019] [<ffffffff81064635>] worker_thread+0x155/0x400
[ 3093.901023] [<ffffffff81069b86>] kthread+0xd6/0xe0
[ 3093.901028] [<ffffffff8145c2fc>] ret_from_fork+0x7c/0xb0
[ 3093.901033]
[ 3093.901033] -> #0 ((&wl->firmware_load)){+.+.+.}:
[ 3093.901037] [<ffffffff810a3d3e>] __lock_acquire+0x14ee/0x1d60
[ 3093.901041] [<ffffffff810a4bf6>] lock_acquire+0xa6/0x1e0
[ 3093.901045] [<ffffffff81062198>] flush_work+0x38/0x2a0
[ 3093.901049] [<ffffffff8106337b>] __cancel_work_timer+0x7b/0xd0
[ 3093.901053] [<ffffffff810633eb>] cancel_work_sync+0xb/0x10
[ 3093.901057] [<ffffffffa047acd5>] b43_wireless_core_stop+0x75/0x250 [b43]
[ 3093.901065] [<ffffffffa047aefc>] b43_op_stop+0x4c/0x90 [b43]
[ 3093.901072] [<ffffffffa053f067>] ieee80211_stop_device+0x67/0x290
[mac80211]
[ 3093.901095] [<ffffffffa0521499>] ieee80211_do_stop+0x4e9/0x9e0 [mac80211]
[ 3093.901112] [<ffffffffa05219a5>] ieee80211_stop+0x15/0x20 [mac80211]
[ 3093.901129] [<ffffffff813aa8ad>] __dev_close_many+0x8d/0xd0
[ 3093.901134] [<ffffffff813aa9b3>] dev_close_many+0x83/0xf0
[ 3093.901137] [<ffffffff813aaadf>] rollback_registered_many+0xbf/0x2c0
[ 3093.901140] [<ffffffff813aacf6>] unregister_netdevice_many+0x16/0x70
[ 3093.901144] [<ffffffffa0523a99>]
ieee80211_remove_interfaces+0xe9/0x1a0 [mac80211]
[ 3093.901161] [<ffffffffa050513a>] ieee80211_unregister_hw+0x5a/0x110
[mac80211]
[ 3093.901176] [<ffffffffa047984a>] b43_ssb_remove+0x8a/0xd0 [b43]
[ 3093.901184] [<ffffffffa00fb3eb>] ssb_device_remove+0x2b/0x40 [ssb]
[ 3093.901192] [<ffffffff812d9f81>] __device_release_driver+0x61/0xd0
[ 3093.901198] [<ffffffff812da878>] driver_detach+0xc8/0xd0
[ 3093.901202] [<ffffffff812d9d68>] bus_remove_driver+0x88/0xe0
[ 3093.901206] [<ffffffff812dad4a>] driver_unregister+0x5a/0x90
[ 3093.901209] [<ffffffffa00fba0d>] ssb_driver_unregister+0xd/0x10 [ssb]
[ 3093.901215] [<ffffffffa04a7ac4>] b43_exit+0x10/0x37 [b43]
[ 3093.901223] [<ffffffff810b0d3a>] sys_delete_module+0x13a/0x290
[ 3093.901228] [<ffffffff8145c3a9>] system_call_fastpath+0x16/0x1b
[ 3093.901231]
[ 3093.901231] other info that might help us debug this:
[ 3093.901231]
[ 3093.901235] Possible unsafe locking scenario:
[ 3093.901235]
[ 3093.901238] CPU0 CPU1
[ 3093.901239] ---- ----
[ 3093.901241] lock(rtnl_mutex);
[ 3093.901244] lock((&wl->firmware_load));
[ 3093.901247] lock(rtnl_mutex);
[ 3093.901250] lock((&wl->firmware_load));
[ 3093.901253]
[ 3093.901253] *** DEADLOCK ***
[ 3093.901253]
[ 3093.901257] 3 locks held by modprobe/5557:
[ 3093.901259] #0: (&__lockdep_no_validate__){......}, at:
[<ffffffff812da7fc>] driver_detach+0x4c/0xd0
[ 3093.901266] #1: (&__lockdep_no_validate__){......}, at:
[<ffffffff812da80a>] driver_detach+0x5a/0xd0
[ 3093.901273] #2: (rtnl_mutex){+.+.+.}, at: [<ffffffff813bd7d2>]
rtnl_lock+0x12/0x20
[ 3093.901279]
[ 3093.901279] stack backtrace:
[ 3093.901283] Pid: 5557, comm: modprobe Not tainted 3.8.0-wl+ #117
[ 3093.901286] Call Trace:
[ 3093.901291] [<ffffffff81453b1a>] print_circular_bug+0x28e/0x29f
[ 3093.901295] [<ffffffff810a3d3e>] __lock_acquire+0x14ee/0x1d60
[ 3093.901302] [<ffffffff81011dba>] ? save_stack_trace+0x2a/0x50
[ 3093.901306] [<ffffffff810a4bf6>] lock_acquire+0xa6/0x1e0
[ 3093.901311] [<ffffffff81062160>] ? work_cpu+0x20/0x20
[ 3093.901315] [<ffffffff81062198>] flush_work+0x38/0x2a0
[ 3093.901319] [<ffffffff81062160>] ? work_cpu+0x20/0x20
[ 3093.901323] [<ffffffff810a557c>] ? mark_held_locks+0x8c/0x110
[ 3093.901329] [<ffffffff81052d27>] ? del_timer+0x57/0x70
[ 3093.901334] [<ffffffff81063368>] ? __cancel_work_timer+0x68/0xd0
[ 3093.901338] [<ffffffff810a5705>] ? trace_hardirqs_on_caller+0x105/0x190
[ 3093.901343] [<ffffffff8106337b>] __cancel_work_timer+0x7b/0xd0
[ 3093.901347] [<ffffffff810633eb>] cancel_work_sync+0xb/0x10
[ 3093.901355] [<ffffffffa047acd5>] b43_wireless_core_stop+0x75/0x250 [b43]
[ 3093.901364] [<ffffffffa047aefc>] b43_op_stop+0x4c/0x90 [b43]
[ 3093.901384] [<ffffffffa053f067>] ieee80211_stop_device+0x67/0x290 [mac80211]
[ 3093.901402] [<ffffffffa0521499>] ieee80211_do_stop+0x4e9/0x9e0 [mac80211]
[ 3093.901407] [<ffffffff813cb0b1>] ? dev_deactivate_many+0x231/0x2f0
[ 3093.901425] [<ffffffffa05219a5>] ieee80211_stop+0x15/0x20 [mac80211]
[ 3093.901429] [<ffffffff813aa8ad>] __dev_close_many+0x8d/0xd0
[ 3093.901433] [<ffffffff813aa9b3>] dev_close_many+0x83/0xf0
[ 3093.901437] [<ffffffff813aaadf>] rollback_registered_many+0xbf/0x2c0
[ 3093.901441] [<ffffffff813aacf6>] unregister_netdevice_many+0x16/0x70
[ 3093.901459] [<ffffffffa0523a99>] ieee80211_remove_interfaces+0xe9/0x1a0
[mac80211]
[ 3093.901475] [<ffffffffa050513a>] ieee80211_unregister_hw+0x5a/0x110 [mac80211]
[ 3093.901484] [<ffffffffa047984a>] b43_ssb_remove+0x8a/0xd0 [b43]
[ 3093.901490] [<ffffffffa00fb3eb>] ssb_device_remove+0x2b/0x40 [ssb]
[ 3093.901495] [<ffffffff812d9f81>] __device_release_driver+0x61/0xd0
[ 3093.901499] [<ffffffff812da878>] driver_detach+0xc8/0xd0
[ 3093.901504] [<ffffffff812d9d68>] bus_remove_driver+0x88/0xe0
[ 3093.901508] [<ffffffff812dad4a>] driver_unregister+0x5a/0x90
[ 3093.901515] [<ffffffffa00fba0d>] ssb_driver_unregister+0xd/0x10 [ssb]
[ 3093.901524] [<ffffffffa04a7ac4>] b43_exit+0x10/0x37 [b43]
[ 3093.901528] [<ffffffff810b0d3a>] sys_delete_module+0x13a/0x290
[ 3093.901532] [<ffffffff810a5705>] ? trace_hardirqs_on_caller+0x105/0x190
[ 3093.901538] [<ffffffff8121affe>] ? trace_hardirqs_on_thunk+0x3a/0x3f
[ 3093.901542] [<ffffffff8145c3a9>] system_call_fastpath+0x16/0x1b
[ 3093.901685] b43-phy1 debug: Wireless interface stopped
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