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Date: Thu, 09 Feb 2012 14:36:16 +0100
From: Johannes Berg <johannes@sipsolutions.net>
MIME-Version: 1.0
To: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
CC: "John W. Linville" <linville@tuxdriver.com>,
	linux-wireless@vger.kernel.org, stable@vger.kernel.org,
	Gary Morain <gmorain@google.com>,
	Paul Stewart <pstew@google.com>,
	Abhijit Pradhan <abhijit@qca.qualcomm.com>,
	Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>,
	Rajkumar Manoharan <rmanohar@qca.qualcomm.com>
Subject: Re: [RFC] mac80211: Fix a rwlock bad magic bug
References: <1328792643-6734-1-git-send-email-mohammed@qca.qualcomm.com>
In-Reply-To: <1328792643-6734-1-git-send-email-mohammed@qca.qualcomm.com>
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On 2/9/2012 2:04 PM, Mohammed Shafi Shajakhan wrote:
> From: Mohammed Shafi Shajakhan<mohammed@qca.qualcomm.com>
>
> read_lock(&tpt_trig->trig.leddev_list_lock) is accessed via the path
> ieee80211_open (->) ieee80211_do_open (->) ieee80211_mod_tpt_led_trig
> (->) ieee80211_start_tpt_led_trig (->) tpt_trig_timer before initializing
> it.
> the intilization of this read/write lock happens via the path
> ieee80211_led_init (->) led_trigger_register, but we are doing
> 'ieee80211_led_init'  after 'ieeee80211_if_add' where we
> register netdev_ops.
> so we access leddev_list_lock before initializing it and causes the
> following bug in chrome laptops with AR928X cards with the following
> script
>
> while true
> do
> sudo modprobe -v ath9k
> sleep 3
> sudo modprobe -r ath9k
> sleep 3
> done
>
> 	BUG: rwlock bad magic on CPU#1, wpa_supplicant/358, f5b9eccc
> 	Pid: 358, comm: wpa_supplicant Not tainted 3.0.13 #1
> 	Call Trace:
>
> 	[<8137b9df>] rwlock_bug+0x3d/0x47
> 	[<81179830>] do_raw_read_lock+0x19/0x29
> 	[<8137f063>] _raw_read_lock+0xd/0xf
> 	[<f9081957>] tpt_trig_timer+0xc3/0x145 [mac80211]
> 	[<f9081f3a>] ieee80211_mod_tpt_led_trig+0x152/0x174 [mac80211]
> 	[<f9076a3f>] ieee80211_do_open+0x11e/0x42e [mac80211]
> 	[<f9075390>] ? ieee80211_check_concurrent_iface+0x26/0x13c [mac80211]
> 	[<f9076d97>] ieee80211_open+0x48/0x4c [mac80211]
> 	[<812dbed8>] __dev_open+0x82/0xab
> 	[<812dc0c9>] __dev_change_flags+0x9c/0x113
> 	[<812dc1ae>] dev_change_flags+0x18/0x44
> 	[<8132144f>] devinet_ioctl+0x243/0x51a
> 	[<81321ba9>] inet_ioctl+0x93/0xac
> 	[<812cc951>] sock_ioctl+0x1c6/0x1ea
> 	[<812cc78b>] ? might_fault+0x20/0x20
> 	[<810b1ebb>] do_vfs_ioctl+0x46e/0x4a2
> 	[<810a6ebb>] ? fget_light+0x2f/0x70
> 	[<812ce549>] ? sys_recvmsg+0x3e/0x48
> 	[<810b1f35>] sys_ioctl+0x46/0x69
> 	[<8137fa77>] sysenter_do_call+0x12/0x2
>
> Cc:<stable@vger.kernel.org>
> Cc: Gary Morain<gmorain@google.com>
> Cc: Paul Stewart<pstew@google.com>
> Cc: Abhijit Pradhan<abhijit@qca.qualcomm.com>
> Cc: Vasanthakumar Thiagarajan<vthiagar@qca.qualcomm.com>
> Cc: Rajkumar Manoharan<rmanohar@qca.qualcomm.com>
> Tested-by: Mohammed Shafi Shajakhan<mohammed@qca.qualcomm.com>
> Signed-off-by: Mohammed Shafi Shajakhan<mohammed@qca.qualcomm.com>

Acked-by: Johannes Berg <johannes.berg@intel.com>


> ---
>   net/mac80211/main.c |    4 ++--
>   1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/mac80211/main.c b/net/mac80211/main.c
> index 831a5bd..2306d75 100644
> --- a/net/mac80211/main.c
> +++ b/net/mac80211/main.c
> @@ -909,6 +909,8 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
>   		wiphy_debug(local->hw.wiphy, "Failed to initialize wep: %d\n",
>   			    result);
>
> +	ieee80211_led_init(local);
> +
>   	rtnl_lock();
>
>   	result = ieee80211_init_rate_ctrl_alg(local,
> @@ -930,8 +932,6 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
>
>   	rtnl_unlock();
>
> -	ieee80211_led_init(local);
> -
>   	local->network_latency_notifier.notifier_call =
>   		ieee80211_max_network_latency;
>   	result = pm_qos_add_notifier(PM_QOS_NETWORK_LATENCY,