Subject: Re: [PATCH] ath9k_htc: add adaptive usb receive flow control to repair soft lockup with monitor mode

From: Oleksij Rempel <[email-masked]>
Date: Mon, 09 Feb 2015 11:06:03 +0100

Hi Yuwei,

here is some review according lates changes.

Please add some comments to the code. Probably it is just me, but it is
hard to get idea of the solution. It can happen that by the next
workorgy i or someone else can skrew it :D

Am 09.02.2015 um 08:13 schrieb [email-masked]:
> From: Yuwei Zheng <[email-masked]>
> 
> In the environment with heavy wifi traffic, set the ar9271 into monitor mode, will
> trigger a deadloop panic.
>  
> The ath9k_hif_usb_rx_cb function excute on  the interrupt context, and ath9k_rx_tasklet excute
> on the soft irq context. In other words, the ath9k_hif_usb_rx_cb have more chance to excute than
> ath9k_rx_tasklet.  So in the worst condition,  the rx.rxbuf receive list is always full,
> and the do {}while(true) loop will not be break. The kernel get a soft lockup panic. 
>  
> [59011.007210] BUG: soft lockup - CPU#0 stuck for 23s!
> [kworker/0:0:30609]
> [59011.030560] BUG: scheduling while atomic: kworker/0:0/30609/0x40010100
> [59013.804486] BUG: scheduling while atomic: kworker/0:0/30609/0x40010100
> [59013.858522] Kernel panic - not syncing: softlockup: hung tasks
>  
> [59014.038891] Exception stack(0xdf4bbc38 to 0xdf4bbc80)
> [59014.046834] bc20:                                                       de57b950 60000113
> [59014.059579] bc40: 00000000 bb32bb32 60000113 de57b948 de57b500 dc7bb440 df4bbcd0 00000000
> [59014.072337] bc60: de57b950 60000113 df4bbcd0 df4bbc80 c04c259d c04c25a0 60000133 ffffffff
> [59014.085233] [<c04c28db>] (__irq_svc+0x3b/0x5c) from [<c04c25a0>] (_raw_spin_unlock_irqrestore+0xc/0x10)
> [59014.100437] [<c04c25a0>] (_raw_spin_unlock_irqrestore+0xc/0x10) from [<bf9c2089>] (ath9k_rx_tasklet+0x290/0x490 [ath9k_htc])
> [59014.118267] [<bf9c2089>] (ath9k_rx_tasklet+0x290/0x490 [ath9k_htc]) from [<c0036d23>] (tasklet_action+0x3b/0x98)
> [59014.134132] [<c0036d23>] (tasklet_action+0x3b/0x98) from [<c0036709>] (__do_softirq+0x99/0x16c)
> [59014.147784] [<c0036709>] (__do_softirq+0x99/0x16c) from [<c00369f7>] (irq_exit+0x5b/0x5c)
> [59014.160653] [<c00369f7>] (irq_exit+0x5b/0x5c) from [<c000cfc3>] (handle_IRQ+0x37/0x78)
> [59014.173124] [<c000cfc3>] (handle_IRQ+0x37/0x78) from [<c00085df>] (omap3_intc_handle_irq+0x5f/0x68)
> [59014.187225] [<c00085df>] (omap3_intc_handle_irq+0x5f/0x68) from [<c04c28db>](__irq_svc+0x3b/0x5c)
>  
> This bug can be see with low performance board, such as uniprocessor beagle bone board. 
>  
> Signed-off-by: Yuwei Zheng <[email-masked]>
> 
> ---
>  drivers/net/wireless/ath/ath9k/hif_usb.c       | 75 +++++++++++++++++++++++---
>  drivers/net/wireless/ath/ath9k/hif_usb.h       |  9 ++++
>  drivers/net/wireless/ath/ath9k/htc.h           | 19 +++++++
>  drivers/net/wireless/ath/ath9k/htc_drv_debug.c | 53 ++++++++++++++++++
>  drivers/net/wireless/ath/ath9k/htc_drv_txrx.c  | 44 +++++++++++++++
>  5 files changed, 193 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
> index 8e7153b..d05cc0b 100644
> --- a/drivers/net/wireless/ath/ath9k/hif_usb.c
> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
> @@ -640,6 +640,7 @@ static void ath9k_hif_usb_rx_cb(struct urb *urb)
>  	struct hif_device_usb *hif_dev =
>  		usb_get_intfdata(usb_ifnum_to_if(urb->dev, 0));
>  	int ret;
> +	int delay;
>  
>  	if (!skb)
>  		return;
> @@ -658,7 +659,6 @@ static void ath9k_hif_usb_rx_cb(struct urb *urb)
>  	default:
>  		goto resubmit;
>  	}
> -

please avoid this small changes

>  	if (likely(urb->actual_length != 0)) {
>  		skb_put(skb, urb->actual_length);
>  		ath9k_hif_usb_rx_stream(hif_dev, skb);
> @@ -667,12 +667,22 @@ static void ath9k_hif_usb_rx_cb(struct urb *urb)
>  resubmit:
>  	skb_reset_tail_pointer(skb);
>  	skb_trim(skb, 0);
> -
> -	usb_anchor_urb(urb, &hif_dev->rx_submitted);
> -	ret = usb_submit_urb(urb, GFP_ATOMIC);
> -	if (ret) {
> -		usb_unanchor_urb(urb);
> -		goto free;
> +	spin_lock(&hif_dev->aurfc_lock);
> +	if (atomic_read(&hif_dev->aurfc_submit_delay) > 0 &&
> +	    hif_dev->aurfc_active == 1) {

why do we need hif_dev->aurfc_active? Is it possible situation where
aurfc_submit_delay) > 0 and hif_dev->aurfc_active == 0?

> +		usb_anchor_urb(urb, &hif_dev->rx_delayed_submitted);
> +		delay = atomic_read(&hif_dev->aurfc_submit_delay);
> +		schedule_delayed_work(&hif_dev->aurfc_delayed_work,
> +				      msecs_to_jiffies(delay));

schedule_delayed_work has internal locks. Do we really need extra locks
here?

> +		spin_unlock(&hif_dev->aurfc_lock);
> +	} else {
> +		spin_unlock(&hif_dev->aurfc_lock);
> +		usb_anchor_urb(urb, &hif_dev->rx_submitted);
> +		ret = usb_submit_urb(urb, GFP_ATOMIC);
> +		if (ret) {
> +			usb_unanchor_urb(urb);
> +			goto free;
> +		}
>  	}
>  
>  	return;
> @@ -818,9 +828,51 @@ err:
>  	return -ENOMEM;
>  }
>  
> +static void aurfc_submit_handler(struct work_struct *work)
> +{
> +	struct hif_device_usb *hif_dev =
> +		container_of(work,
> +			     struct hif_device_usb,
> +			     aurfc_delayed_work.work);
> +	struct urb *urb = NULL;
> +	struct sk_buff *skb = NULL;
> +	int ret;
> +	int loop_times = 0;
> +
> +	AURFC_STAT_INC(aurfc_called);
> +	while (true) {
> +		loop_times++;
> +		if (loop_times > MAX_RX_URB_NUM)
> +			atomic_add(AURFC_STEP,
> +				   &hif_dev->aurfc_submit_delay);
> +
> +		urb = usb_get_from_anchor(
> +				&hif_dev->rx_delayed_submitted);
> +		if (urb) {
> +			skb = (struct sk_buff *)urb->context;
> +			ret = usb_submit_urb(urb, GFP_KERNEL);
> +			if (ret != 0) {
> +				usb_unanchor_urb(urb);
> +				dev_kfree_skb_any(skb);
> +				urb->context = NULL;
> +			}
> +		} else {
> +			break;
> +		}
> +	}
> +}
> +
>  static void ath9k_hif_usb_dealloc_rx_urbs(struct hif_device_usb *hif_dev)
>  {
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&hif_dev->aurfc_lock, flags);

really needed?

> +	hif_dev->aurfc_active = 0;

same here?

> +	mod_delayed_work(system_wq, &hif_dev->aurfc_delayed_work, 0);

flush_delayed_work - "Delayed timer is cancelled and the pending work is
queued for immediate execution". No need to modify timer here.

> +	spin_unlock_irqrestore(&hif_dev->aurfc_lock, flags);
> +	flush_delayed_work(&hif_dev->aurfc_delayed_work);
>  	usb_kill_anchored_urbs(&hif_dev->rx_submitted);
> +	usb_kill_anchored_urbs(&hif_dev->rx_delayed_submitted);
>  }
>  
>  static int ath9k_hif_usb_alloc_rx_urbs(struct hif_device_usb *hif_dev)
> @@ -830,8 +882,17 @@ static int ath9k_hif_usb_alloc_rx_urbs(struct hif_device_usb *hif_dev)
>  	int i, ret;
>  
>  	init_usb_anchor(&hif_dev->rx_submitted);
> +	init_usb_anchor(&hif_dev->rx_delayed_submitted);
> +
>  	spin_lock_init(&hif_dev->rx_lock);
>  
> +	/* add for adaptive usb receive control*/
> +	atomic_set(&hif_dev->aurfc_submit_delay, 0);
> +	INIT_DELAYED_WORK(&hif_dev->aurfc_delayed_work,
> +			  aurfc_submit_handler);
> +	spin_lock_init(&hif_dev->aurfc_lock);
> +	hif_dev->aurfc_active = 1;

aurfc_active and aurfc_lock - do we really need it?

>  	for (i = 0; i < MAX_RX_URB_NUM; i++) {
>  
>  		/* Allocate URB */
> diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.h b/drivers/net/wireless/ath/ath9k/hif_usb.h
> index 51496e7..8e7b67e 100644
> --- a/drivers/net/wireless/ath/ath9k/hif_usb.h
> +++ b/drivers/net/wireless/ath/ath9k/hif_usb.h
> @@ -41,6 +41,7 @@
>  #define MAX_RX_URB_NUM  8
>  #define MAX_RX_BUF_SIZE 16384
>  #define MAX_PKT_NUM_IN_TRANSFER 10
> +#define AURFC_STEP 70  /* ms */
>  
>  #define MAX_REG_OUT_URB_NUM  1
>  #define MAX_REG_IN_URB_NUM   64
> @@ -98,9 +99,17 @@ struct hif_device_usb {
>  	struct hif_usb_tx tx;
>  	struct usb_anchor regout_submitted;
>  	struct usb_anchor rx_submitted;
> +	struct usb_anchor rx_delayed_submitted;
>  	struct usb_anchor reg_in_submitted;
>  	struct usb_anchor mgmt_submitted;
>  	struct sk_buff *remain_skb;
> +
> +	/* adaptive usb receive flow control */
> +	struct delayed_work aurfc_delayed_work;
> +	spinlock_t aurfc_lock; /* to protect work */
> +	atomic_t  aurfc_submit_delay; /* ms */
> +	int aurfc_active;
> +
>  	const char *fw_name;
>  	int rx_remain_len;
>  	int rx_pkt_len;
> diff --git a/drivers/net/wireless/ath/ath9k/htc.h b/drivers/net/wireless/ath/ath9k/htc.h
> index 9dde265..1586bd2 100644
> --- a/drivers/net/wireless/ath/ath9k/htc.h
> +++ b/drivers/net/wireless/ath/ath9k/htc.h
> @@ -331,6 +331,13 @@ static inline struct ath9k_htc_tx_ctl *HTC_SKB_CB(struct sk_buff *skb)
>  
>  #define TX_QSTAT_INC(q) (priv->debug.tx_stats.queue_stats[q]++)
>  
> +#define AURFC_STAT_INC(c) \
> +	(hif_dev->htc_handle->drv_priv->debug.aurfc_stats.c++)
> +#define AURFC_STAT_ADD(c, a) \
> +	(hif_dev->htc_handle->drv_priv->debug.aurfc_stats.c += a)
> +#define AURFC_STAT_SET(c, a) \
> +	(hif_dev->htc_handle->drv_priv->debug.aurfc_stats.c = a)
> +
>  void ath9k_htc_err_stat_rx(struct ath9k_htc_priv *priv,
>  			   struct ath_rx_status *rs);
>  
> @@ -352,11 +359,20 @@ struct ath_skbrx_stats {
>  	u32 skb_dropped;
>  };
>  
> +struct ath_aurfc_stats {
> +	u32 aurfc_highwater;
> +	u32 aurfc_lowwater;
> +	u32 aurfc_wm_triggered;
> +	u32 aurfc_submit_delay;
> +	u32 aurfc_called;
> +};
> +
>  struct ath9k_debug {
>  	struct dentry *debugfs_phy;
>  	struct ath_tx_stats tx_stats;
>  	struct ath_rx_stats rx_stats;
>  	struct ath_skbrx_stats skbrx_stats;
> +	struct ath_aurfc_stats aurfc_stats;
>  };
>  
>  void ath9k_htc_get_et_strings(struct ieee80211_hw *hw,
> @@ -377,6 +393,9 @@ void ath9k_htc_get_et_stats(struct ieee80211_hw *hw,
>  
>  #define TX_QSTAT_INC(c) do { } while (0)
>  
> +#define AURFC_STAT_INC(c) do {} while (0)
> +#define AURFC_STAT_ADD(c, a) do {} while (0)
> +#define AURFC_STAT_SET(c, a) do {} while (0)
>  static inline void ath9k_htc_err_stat_rx(struct ath9k_htc_priv *priv,
>  					 struct ath_rx_status *rs)
>  {
> diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_debug.c b/drivers/net/wireless/ath/ath9k/htc_drv_debug.c
> index 8cef1ed..a6be9be 100644
> --- a/drivers/net/wireless/ath/ath9k/htc_drv_debug.c
> +++ b/drivers/net/wireless/ath/ath9k/htc_drv_debug.c
> @@ -286,6 +286,54 @@ static const struct file_operations fops_skb_rx = {
>  	.llseek = default_llseek,
>  };
>  
> +static ssize_t read_file_aurfc(struct file *file,
> +			       char __user *user_buf,
> +			       size_t count, loff_t *ppos)
> +{
> +	struct ath9k_htc_priv *priv = file->private_data;
> +	char *buf;
> +	unsigned int len = 0, size = 1500;
> +	ssize_t retval = 0;
> +
> +	buf = kzalloc(size, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	len += scnprintf(buf + len, size - len,
> +			"%20s : %10u\n", "High watermark",
> +			priv->debug.aurfc_stats.aurfc_highwater);
> +	len += scnprintf(buf + len, size - len,
> +			"%20s : %10u\n", "Low watermark",
> +			priv->debug.aurfc_stats.aurfc_lowwater);
> +
> +	len += scnprintf(buf + len, size - len,
> +			"%20s : %10u\n", "WM triggered",
> +			priv->debug.aurfc_stats.aurfc_wm_triggered);
> +
> +	len += scnprintf(buf + len, size - len,
> +			"%20s : %10u\n", "Handler called",
> +			priv->debug.aurfc_stats.aurfc_called);
> +
> +	len += scnprintf(buf + len, size - len,
> +			"%20s : %10u\n", "Submit delay",
> +			priv->debug.aurfc_stats.aurfc_submit_delay);
> +	if (len > size)
> +		len = size;
> +
> +	retval = simple_read_from_buffer(user_buf, count,
> +					 ppos, buf, len);
> +	kfree(buf);
> +
> +	return retval;
> +}
> +
> +static const struct file_operations fops_aurfc = {
> +	.read = read_file_aurfc,
> +	.open = simple_open,
> +	.owner = THIS_MODULE,
> +	.llseek = default_llseek,
> +};
> +
>  static ssize_t read_file_slot(struct file *file, char __user *user_buf,
>  			      size_t count, loff_t *ppos)
>  {
> @@ -518,7 +566,12 @@ int ath9k_htc_init_debug(struct ath_hw *ah)
>  	debugfs_create_file("skb_rx", S_IRUSR, priv->debug.debugfs_phy,
>  			    priv, &fops_skb_rx);
>  
> +	debugfs_create_file("aurfc_stats", S_IRUSR,
> +			    priv->debug.debugfs_phy,
> +			    priv, &fops_aurfc);
> +
>  	ath9k_cmn_debug_recv(priv->debug.debugfs_phy, &priv->debug.rx_stats);
> +
>  	ath9k_cmn_debug_phy_err(priv->debug.debugfs_phy, &priv->debug.rx_stats);
>  
>  	debugfs_create_file("slot", S_IRUSR, priv->debug.debugfs_phy,
> diff --git a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
> index a0f58e2..939d008 100644
> --- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
> +++ b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
> @@ -1061,7 +1061,28 @@ void ath9k_rx_tasklet(unsigned long data)
>  	unsigned long flags;
>  	struct ieee80211_hdr *hdr;
>  
> +	/* add for adaptive usb receive flow control*/
> +	int looptimes = 0;
> +	int highwatermark = ATH9K_HTC_RXBUF*3/4;
> +	int lowwatermark = ATH9K_HTC_RXBUF/32;
> +	unsigned int delay = 0;
> +
> +	struct htc_target *htc = priv->htc;
> +	struct hif_device_usb *hif_dev = htc->hif_dev;
> +
> +	AURFC_STAT_SET(aurfc_highwater, highwatermark);
> +	AURFC_STAT_SET(aurfc_lowwater, lowwatermark);
> +
>  	do {
> +		looptimes++;
> +		if (looptimes > highwatermark) {
> +			delay = looptimes*AURFC_STEP;
> +			atomic_set(&hif_dev->aurfc_submit_delay,
> +				   delay);
> +			AURFC_STAT_INC(aurfc_wm_triggered);
> +			AURFC_STAT_SET(aurfc_submit_delay, delay);
> +		}
> +
>  		spin_lock_irqsave(&priv->rx.rxbuflock, flags);
>  		list_for_each_entry(tmp_buf, &priv->rx.rxbuf, list) {
>  			if (tmp_buf->in_process) {
> @@ -1072,6 +1093,22 @@ void ath9k_rx_tasklet(unsigned long data)
>  
>  		if (rxbuf == NULL) {
>  			spin_unlock_irqrestore(&priv->rx.rxbuflock, flags);
> +			spin_lock_irqsave(&hif_dev->aurfc_lock,
> +					  flags);
> +			if (atomic_read(
> +				&hif_dev->aurfc_submit_delay) > 0 &&
> +			    hif_dev->aurfc_active > 0)
> +				mod_delayed_work(system_wq,
> +					&hif_dev->aurfc_delayed_work,
> +						 0);

mod_delayed_work or may be you mean flush_delayed_work? In both cases,
local irqs are disabled.

> +			spin_unlock_irqrestore(&hif_dev->aurfc_lock,
> +					       flags);
> +			if (looptimes < lowwatermark) {
> +				atomic_set(&hif_dev->aurfc_submit_delay
> +					   , 0);
> +				AURFC_STAT_SET(aurfc_submit_delay,
> +					       0);
> +			}
>  			break;
>  		}
>  
> @@ -1114,6 +1151,10 @@ void ath9k_htc_rxep(void *drv_priv, struct sk_buff *skb,
>  	struct ath_common *common = ath9k_hw_common(ah);
>  	struct ath9k_htc_rxbuf *rxbuf = NULL, *tmp_buf = NULL;
>  

please, no space here.

> +	struct htc_target *htc = priv->htc;
> +	struct hif_device_usb *hif_dev = htc->hif_dev;
> +	int delay = ATH9K_HTC_RXBUF * AURFC_STEP;
> +
>  	spin_lock(&priv->rx.rxbuflock);
>  	list_for_each_entry(tmp_buf, &priv->rx.rxbuf, list) {
>  		if (!tmp_buf->in_process) {
> @@ -1124,6 +1165,9 @@ void ath9k_htc_rxep(void *drv_priv, struct sk_buff *skb,
>  	spin_unlock(&priv->rx.rxbuflock);
>  
>  	if (rxbuf == NULL) {
> +		atomic_set(&hif_dev->aurfc_submit_delay, delay);
> +		AURFC_STAT_INC(aurfc_wm_triggered);
> +		AURFC_STAT_SET(aurfc_submit_delay, delay);
>  		ath_dbg(common, ANY, "No free RX buffer\n");
>  		goto err;
>  	}
> 

-- 
Regards,
Oleksij