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Date: Wed, 2 May 2012 10:32:05 +0530
Message-ID: <CAD2nsn14nu_N-3zZ5NdOMAJg6m6uPVD_ai0fAORvQqC2JVdPMw@mail.gmail.com> (sfid-20120502_070212_729593_3B4C552A)
Subject: Re: Suspicious RCU usage in mac80211
From: Mohammed Shafi <shafi.wireless@gmail.com>
To: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Johannes Berg <johannes@sipsolutions.net>,
	wireless <linux-wireless@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>
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On Wed, May 2, 2012 at 12:48 AM, Larry Finger <Larry.Finger@lwfinger.net> wrote:
> On 05/01/2012 09:25 AM, Mohammed Shafi wrote:
>>
>>
>> i just looked into the code and compared it with
>> sta_addba_resp_timer_expired and thought whether we should do
>> this..
>
>
> Your patch does not help. I still get the following dump in the log:

Larry, thanks for trying it out. then there seems to be something else, which
requires further debugging/understanding.

>
> ===============================
> [ INFO: suspicious RCU usage. ]
> 3.4.0-rc5-wl+ #287 Not tainted
> -------------------------------
>
> net/mac80211/sta_info.h:456 suspicious rcu_dereference_protected() usage!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 0
> 3 locks held by kmemleak/622:
> #0: ?(scan_mutex){+.+...}, at: [<ffffffff8113b0d6>]
> kmemleak_scan_thread+0x56/0xd0
> #1: ?(&tid_tx->session_timer){+.-...}, at: [<ffffffff8104853a>]
> run_timer_softirq+0xfa/0x6e0
> #2: ?(rcu_read_lock){.+.+..}, at: [<ffffffffa0449ff0>]
> sta_tx_agg_session_timer_expired+0x0/0x2a0 [mac80211]
>
> stack backtrace:
> Pid: 622, comm: kmemleak Not tainted 3.4.0-rc5-wl+ #287
> Call Trace:
> ?<IRQ> ?[<ffffffff8109309d>] lockdep_rcu_suspicious+0xfd/0x130
> ?[<ffffffffa044a1cf>] sta_tx_agg_session_timer_expired+0x1df/0x2a0
> [mac80211]
> ?[<ffffffffa0449ff0>] ? ieee80211_start_tx_ba_session+0x450/0x450 [mac80211]
> ?[<ffffffff810485c5>] run_timer_softirq+0x185/0x6e0
>
> As kmemleak seems to be involved, I have added Catalin Marinas to the Cc
> list.
>
> Larry
>
>

-- 
thanks,
shafi