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Message-ID: <4EEB42A5.7050805@qca.qualcomm.com> (sfid-20111216_140801_455933_525E76A5)
Date: Fri, 16 Dec 2011 18:37:49 +0530
From: Mohammed Shafi Shajakhan <mohammed@qca.qualcomm.com>
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To: Felix Fietkau <nbd@openwrt.org>
CC: "John W. Linville" <linville@tuxdriver.com>,
	Jouni Malinen <jouni@qca.qualcomm.com>,
	<linux-wireless@vger.kernel.org>,
	Rodriguez Luis <rodrigue@qca.qualcomm.com>,
	Balasubramanian senthilkumar <senthilb@qca.qualcomm.com>,
	Vasanthakumar Thiagarajan <vthiagar@qca.qualcomm.com>,
	Rajkumar Manoharan <rmanohar@qca.qualcomm.com>,
	Vivek Natarajan <nataraja@qca.qualcomm.com>,
	<ath9k-devel@lists.ath9k.org>
Subject: Re: [PATCH 1/1] ath9k: fix a soft lockup
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On Friday 16 December 2011 06:35 PM, Mohammed Shafi Shajakhan wrote:
> From: Mohammed Shafi Shajakhan<mohammed@qca.qualcomm.com>
>
> with the recent changes in the tx path we got a soft lockup.
> introduced by the commit 3ad2952998b08442044690fa9b4ec38c6c3fc4a9
> ath_send_bar seems to later call ath9k_tx which in turn seems to
> acquire the same axq_lock before calling ath_tx_start_dma

this seems to fix the softlock up with my preliminary testing.
if some one finds a flaw in this or a better fix please feel free
to resend. i will be out of station for two days.

>
> Call Trace:
> [<c03ba9ae>] __delay+0xe/0x10
> [<c03c1dc2>] do_raw_spin_lock+0xb2/0x100
> [<c0671a67>] _raw_spin_lock_bh+0x67/0x80
> [<f984aa81>] ? ath_tx_start+0x151/0x4c0 [ath9k]
> [<f984aa81>] ath_tx_start+0x151/0x4c0 [ath9k]
> [<f984248c>] ath9k_tx+0x9c/0x1f0 [ath9k]
> [<f97eae3e>] __ieee80211_tx+0x18e/0x2d0 [mac80211]
> [<f97ec9ac>] ieee80211_tx+0xfc/0x130 [mac80211]
> [<f97ec8e3>] ? ieee80211_tx+0x33/0x130 [mac80211]
> [<f97ecd88>] ieee80211_xmit+0xc8/0x130 [mac80211]
> [<f97eccc0>] ? ieee80211_tx_pending+0x2e0/0x2e0
> [mac80211]
> [<f97ece3d>] ieee80211_tx_skb_tid+0x4d/0x60 [mac80211]
> [<f97ceda4>] ieee80211_send_bar+0xd4/0xf0 [mac80211]
> [<f984a04a>] ath_tx_complete_aggr+0x52a/0xaa0 [ath9k]
> [<f9849bd0>] ? ath_tx_complete_aggr+0xb0/0xaa0 [ath9k]
> [<f9840029>] ? setup_ht_cap+0x169/0x180 [ath9k]
> [<f984b606>] ? ath_tx_edma_tasklet+0x76/0x2a0 [ath9k]
> [<f984b606>] ? ath_tx_edma_tasklet+0x76/0x2a0 [ath9k]
> [<f984a628>] ath_tx_process_buffer+0x68/0xe0 [ath9k]
> [<f984b705>] ath_tx_edma_tasklet+0x175/0x2a0 [ath9k]
> [<f983fc2d>] ? ath9k_ioread32+0x2d/0x70 [ath9k]
> [<f9842b4b>] ath9k_tasklet+0x10b/0x1c0 [ath9k]
>
> Signed-off-by: Mohammed Shafi Shajakhan<mohammed@qca.qualcomm.com>
> ---
>   drivers/net/wireless/ath/ath9k/xmit.c |    7 ++++++-
>   1 files changed, 6 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
> index 23e80e6..ef81df0 100644
> --- a/drivers/net/wireless/ath/ath9k/xmit.c
> +++ b/drivers/net/wireless/ath/ath9k/xmit.c
> @@ -189,8 +189,11 @@ static void ath_tx_flush_tid(struct ath_softc *sc, struct ath_atx_tid *tid)
>   		tid->state&= ~AGGR_CLEANUP;
>   	}
>
> -	if (sendbar)
> +	if (sendbar) {
> +		spin_unlock_bh(&txq->axq_lock);
>   		ath_send_bar(tid, tid->seq_start);
> +		spin_lock_bh(&txq->axq_lock);
> +	}
>   }
>
>   static void ath_tx_update_baw(struct ath_softc *sc, struct ath_atx_tid *tid,
> @@ -556,7 +559,9 @@ static void ath_tx_complete_aggr(struct ath_softc *sc, struct ath_txq *txq,
>
>   	if (bar_index>= 0) {
>   		u16 bar_seq = ATH_BA_INDEX2SEQ(seq_first, bar_index);
> +		spin_unlock_bh(&txq->axq_lock);
>   		ath_send_bar(tid, ATH_BA_INDEX2SEQ(seq_first, bar_index + 1));
> +		spin_lock_bh(&txq->axq_lock);
>   		if (BAW_WITHIN(tid->seq_start, tid->baw_size, bar_seq))
>   			tid->bar_index = ATH_BA_INDEX(tid->seq_start, bar_seq);
>   	}


-- 
thanks,
shafi