* lockdep splat related to wifi regulatory in 3.3.6+
@ 2012-05-18 22:45 Ben Greear
2012-05-19 22:42 ` Eliad Peller
0 siblings, 1 reply; 4+ messages in thread
From: Ben Greear @ 2012-05-18 22:45 UTC (permalink / raw)
To: linux-wireless
This appears to be this bug:
https://bugzilla.redhat.com/show_bug.cgi?id=734519
Test case was to create 40 (virtual) stations against an AP that can only handle
30, so the remaining 10 constantly try to re-associate, get DHCP if
they manage, etc....
cfg80211: Calling CRDA for country: US
======================================================
[ INFO: possible circular locking dependency detected ]
3.3.6+ #1 Tainted: G WC O
-------------------------------------------------------
kworker/1:2/62 is trying to acquire lock:
(cfg80211_mutex){+.+.+.}, at: [<ffffffffa00f7ced>] restore_regulatory_settings+0x2c/0x4af [cfg80211]
but task is already holding lock:
((reg_timeout).work){+.+...}, at: [<ffffffff8104c5c1>] process_one_work+0x1c2/0x35a
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 ((reg_timeout).work){+.+...}:
[<ffffffff810799bb>] lock_acquire+0x64/0x81
[<ffffffff8104e038>] wait_on_work+0x54/0xd3
[<ffffffff8104e196>] __cancel_work_timer+0xdf/0x128
[<ffffffff8104e1ec>] cancel_delayed_work_sync+0xd/0xf
[<ffffffffa00f81f5>] reg_set_request_processed+0x4c/0x66 [cfg80211]
[<ffffffffa00f9675>] set_regdom+0x5f8/0x69f [cfg80211]
[<ffffffffa01069ab>] nl80211_set_reg+0x213/0x26c [cfg80211]
[<ffffffff813da541>] genl_rcv_msg+0x1f4/0x239
[<ffffffff813d921d>] netlink_rcv_skb+0x3e/0x8f
[<ffffffff813da346>] genl_rcv+0x21/0x28
[<ffffffff813d8ff8>] netlink_unicast+0xe9/0x152
[<ffffffff813d9777>] netlink_sendmsg+0x1f8/0x216
[<ffffffff813a5d3d>] __sock_sendmsg_nosec+0x5f/0x6a
[<ffffffff813a5d85>] __sock_sendmsg+0x3d/0x48
[<ffffffff813a662f>] sock_sendmsg+0xa3/0xbc
[<ffffffff813a6e38>] __sys_sendmsg+0x20f/0x29c
[<ffffffff813a702e>] sys_sendmsg+0x3d/0x5b
[<ffffffff8147cd79>] system_call_fastpath+0x16/0x1b
-> #1 (reg_mutex){+.+.+.}:
[<ffffffff810799bb>] lock_acquire+0x64/0x81
[<ffffffff81475319>] __mutex_lock_common+0x64/0x4b5
[<ffffffff81475851>] mutex_lock_nested+0x36/0x3b
[<ffffffffa00f8bd3>] reg_todo+0x2d/0x4d7 [cfg80211]
[<ffffffff8104c622>] process_one_work+0x223/0x35a
[<ffffffff8104eac5>] worker_thread+0x136/0x255
[<ffffffff810526be>] kthread+0x84/0x8c
[<ffffffff8147e1b4>] kernel_thread_helper+0x4/0x10
-> #0 (cfg80211_mutex){+.+.+.}:
[<ffffffff81079667>] __lock_acquire+0xade/0xdce
[<ffffffff810799bb>] lock_acquire+0x64/0x81
[<ffffffff81475319>] __mutex_lock_common+0x64/0x4b5
[<ffffffff81475851>] mutex_lock_nested+0x36/0x3b
[<ffffffffa00f7ced>] restore_regulatory_settings+0x2c/0x4af [cfg80211]
[<ffffffffa00f818c>] reg_timeout_work+0x1c/0x1e [cfg80211]
[<ffffffff8104c622>] process_one_work+0x223/0x35a
[<ffffffff8104eac5>] worker_thread+0x136/0x255
[<ffffffff810526be>] kthread+0x84/0x8c
[<ffffffff8147e1b4>] kernel_thread_helper+0x4/0x10
other info that might help us debug this:
Chain exists of:
cfg80211_mutex --> reg_mutex --> (reg_timeout).work
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock((reg_timeout).work);
lock(reg_mutex);
lock((reg_timeout).work);
lock(cfg80211_mutex);
*** DEADLOCK ***
2 locks held by kworker/1:2/62:
#0: (events){.+.+.+}, at: [<ffffffff8104c5c1>] process_one_work+0x1c2/0x35a
#1: ((reg_timeout).work){+.+...}, at: [<ffffffff8104c5c1>] process_one_work+0x1c2/0x35a
stack backtrace:
Pid: 62, comm: kworker/1:2 Tainted: G WC O 3.3.6+ #1
Call Trace:
[<ffffffff810779a6>] print_circular_bug+0x1ff/0x210
[<ffffffff81079667>] __lock_acquire+0xade/0xdce
[<ffffffff8105c5e0>] ? get_parent_ip+0x11/0x42
[<ffffffff810799bb>] lock_acquire+0x64/0x81
[<ffffffffa00f7ced>] ? restore_regulatory_settings+0x2c/0x4af [cfg80211]
[<ffffffff8147af6a>] ? add_preempt_count+0xad/0xb1
[<ffffffff81475319>] __mutex_lock_common+0x64/0x4b5
[<ffffffffa00f7ced>] ? restore_regulatory_settings+0x2c/0x4af [cfg80211]
[<ffffffff81078905>] ? trace_hardirqs_on+0xd/0xf
[<ffffffffa00f7ced>] ? restore_regulatory_settings+0x2c/0x4af [cfg80211]
[<ffffffff81475851>] mutex_lock_nested+0x36/0x3b
[<ffffffffa00f7ced>] restore_regulatory_settings+0x2c/0x4af [cfg80211]
[<ffffffffa00f818c>] reg_timeout_work+0x1c/0x1e [cfg80211]
[<ffffffff8104c622>] process_one_work+0x223/0x35a
[<ffffffff8104c5c1>] ? process_one_work+0x1c2/0x35a
[<ffffffffa00f8170>] ? restore_regulatory_settings+0x4af/0x4af [cfg80211]
[<ffffffff8104eac5>] worker_thread+0x136/0x255
[<ffffffff8104e98f>] ? manage_workers+0x191/0x191
[<ffffffff810526be>] kthread+0x84/0x8c
[<ffffffff8147e1b4>] kernel_thread_helper+0x4/0x10
[<ffffffff81477fb8>] ? retint_restore_args+0x13/0x13
[<ffffffff8105263a>] ? __init_kthread_worker+0x56/0x56
[<ffffffff8147e1b0>] ? gs_change+0x13/0x13
cfg80211: Restoring regulatory settings including user preference
Thanks,
Ben
--
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc http://www.candelatech.com
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: lockdep splat related to wifi regulatory in 3.3.6+
2012-05-18 22:45 lockdep splat related to wifi regulatory in 3.3.6+ Ben Greear
@ 2012-05-19 22:42 ` Eliad Peller
2012-05-21 16:26 ` Ben Greear
0 siblings, 1 reply; 4+ messages in thread
From: Eliad Peller @ 2012-05-19 22:42 UTC (permalink / raw)
To: Ben Greear; +Cc: linux-wireless
hi Ben,
On Sat, May 19, 2012 at 1:45 AM, Ben Greear <greearb@candelatech.com> wrote:
> This appears to be this bug:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=734519
>
> Test case was to create 40 (virtual) stations against an AP that can only
> handle
> 30, so the remaining 10 constantly try to re-associate, get DHCP if
> they manage, etc....
>
>
> cfg80211: Calling CRDA for country: US
>
> ======================================================
> [ INFO: possible circular locking dependency detected ]
> 3.3.6+ #1 Tainted: G WC O
> -------------------------------------------------------
> kworker/1:2/62 is trying to acquire lock:
> (cfg80211_mutex){+.+.+.}, at: [<ffffffffa00f7ced>]
> restore_regulatory_settings+0x2c/0x4af [cfg80211]
>
> but task is already holding lock:
> ((reg_timeout).work){+.+...}, at: [<ffffffff8104c5c1>]
> process_one_work+0x1c2/0x35a
>
> which lock already depends on the new lock.
>
Try this:
http://www.spinics.net/lists/linux-wireless/msg90322.html
Eliad.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: lockdep splat related to wifi regulatory in 3.3.6+
2012-05-19 22:42 ` Eliad Peller
@ 2012-05-21 16:26 ` Ben Greear
2012-05-21 16:48 ` Eliad Peller
0 siblings, 1 reply; 4+ messages in thread
From: Ben Greear @ 2012-05-21 16:26 UTC (permalink / raw)
To: Eliad Peller; +Cc: linux-wireless
On 05/19/2012 03:42 PM, Eliad Peller wrote:
> hi Ben,
>
> On Sat, May 19, 2012 at 1:45 AM, Ben Greear<greearb@candelatech.com> wrote:
>> This appears to be this bug:
>>
>> https://bugzilla.redhat.com/show_bug.cgi?id=734519
>>
>> Test case was to create 40 (virtual) stations against an AP that can only
>> handle
>> 30, so the remaining 10 constantly try to re-associate, get DHCP if
>> they manage, etc....
Thanks, I will try your patch.
But, it has a fairly scary comment about race conditions.
Any idea why sort of symptoms I might see from this potential
race?
Thanks,
Ben
--
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc http://www.candelatech.com
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: lockdep splat related to wifi regulatory in 3.3.6+
2012-05-21 16:26 ` Ben Greear
@ 2012-05-21 16:48 ` Eliad Peller
0 siblings, 0 replies; 4+ messages in thread
From: Eliad Peller @ 2012-05-21 16:48 UTC (permalink / raw)
To: Ben Greear; +Cc: linux-wireless
On Mon, May 21, 2012 at 7:26 PM, Ben Greear <greearb@candelatech.com> wrote:
> On 05/19/2012 03:42 PM, Eliad Peller wrote:
>
> Thanks, I will try your patch.
>
> But, it has a fairly scary comment about race conditions.
> Any idea why sort of symptoms I might see from this potential
> race?
>
i think that in the worst case it will cause a wrong regulatory domain
to be used (i.e. the global regulatory settings will be restored
although a new regdomain was set). however, it's pretty unlinely, and
probably still better than deadlocking...
Eliad.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2012-05-21 16:48 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2012-05-18 22:45 lockdep splat related to wifi regulatory in 3.3.6+ Ben Greear
2012-05-19 22:42 ` Eliad Peller
2012-05-21 16:26 ` Ben Greear
2012-05-21 16:48 ` Eliad Peller
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