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Subject[PATCHv2] ath9k_htc: add adaptive usb receive flow control to repair soft lockup with monitor mode
Date
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. Add some debug
message in the ath9k_hif_usb_rx_cb function may trigger this bug quickly.

Signed-off-by: Yuwei Zheng <yuweizheng@139.com>
---
Changes since v1:
- Add aurfc_active flag to stop delayed submit while ath9k_hif_usb_dealloc_rx_urbs called.
- Add spinlock aurfc_lock to protect aurfc_delayed_work and aurfc_active.
- Add mod_delayed_work to trigger aurfc_submit_handler excuted immediately while rx_buf list is empty.
- Add flush_delayed_work to wait the aurfc_submit_handler finish.

drivers/net/wireless/ath/ath9k/hif_usb.c | 78 +++++++++++++++++++++++---
drivers/net/wireless/ath/ath9k/hif_usb.h | 13 +++++
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 | 58 +++++++++++++++++++
5 files changed, 214 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..2e73e19 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;
}
-
if (likely(urb->actual_length != 0)) {
skb_put(skb, urb->actual_length);
ath9k_hif_usb_rx_stream(hif_dev, skb);
@@ -667,12 +667,23 @@ 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);
+ /* submit the urb more slowly for flow control */
+ if (atomic_read(&hif_dev->aurfc_submit_delay) > 0 &&
+ hif_dev->aurfc_active == 1) {
+ 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));
+ 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 +829,53 @@ 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);
+ hif_dev->aurfc_active = 0;
+ /* excute the last queued work immediately */
+ mod_delayed_work(system_wq, &hif_dev->aurfc_delayed_work, 0);
+ spin_unlock_irqrestore(&hif_dev->aurfc_lock, flags);
+ /* wait the last work finish, otherwise kill urbs may deadlock*/
+ 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 +885,17 @@ 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 flow 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;
+
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..2ff59be 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 /* millisecond */

#define MAX_REG_OUT_URB_NUM 1
#define MAX_REG_IN_URB_NUM 64
@@ -98,9 +99,21 @@ struct hif_device_usb {
struct hif_usb_tx tx;
struct usb_anchor regout_submitted;
struct usb_anchor rx_submitted;
+ /* anchor delayed urb */
+ 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;
+ /* to protect the delayed work */
+ spinlock_t aurfc_lock;
+ /* urb submit delay, in millisecond */
+ atomic_t aurfc_submit_delay;
+ /* set to 1, if the urb can be delayed submit */
+ 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..1c8ebc5 100644
--- a/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
+++ b/drivers/net/wireless/ath/ath9k/htc_drv_txrx.c
@@ -1061,7 +1061,31 @@ 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++;
+ /* when trigger high wartermark, tell the
+ * urb callback to submit more slowlly.
+ */
+ 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 +1096,29 @@ 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);
+ /* the rxbuf list is empty now, the
+ * queued work could be scheduled
+ * to submit urbs immediately.
+ */
+ 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);
+ spin_unlock_irqrestore(&hif_dev->aurfc_lock,
+ flags);
+ /* reset submit delay to guaranteed
+ * usb receive performance.
+ */
+ if (looptimes < lowwatermark) {
+ atomic_set(&hif_dev->aurfc_submit_delay
+ , 0);
+ AURFC_STAT_SET(aurfc_submit_delay,
+ 0);
+ }
break;
}

@@ -1114,6 +1161,10 @@ 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;

+ 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 +1175,13 @@ void ath9k_htc_rxep(void *drv_priv, struct sk_buff *skb,
spin_unlock(&priv->rx.rxbuflock);

if (rxbuf == NULL) {
+ /* The rxbuf list is full now, tell the urb callback
+ * to submit more slowly. Otherwise, the soft lockup
+ * may be triggerd immediately.
+ */
+ 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;
}
--
1.9.1



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