zd1211rw: use urb anchors for tx and fix tx-queue disabling

When stress testing AP-mode I hit OOPS when unpluging or rmmodding
driver.

It appears that when tx-queue is disabled, tx-urbs might be left pending.
These can cause ehci to call non-existing tx_urb_complete() (after rmmod)
or uninitialized/reseted private structure (after disconnect()). Add skb
queue for submitted packets and unlink pending urbs on zd_usb_disable_tx().

Part of the problem seems to be usb->free_urb_list that isn't always
working as it should, causing machine freeze when trying to free the list
in zd_usb_disable_tx(). Caching free urbs isn't what other drivers seem
to be doing (usbnet for example) so strip free_usb_list.

Patch makes tx-urb handling saner with use of urb anchors.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 41 insertions, 75 deletions

diff --git a/drivers/net/wireless/zd1211rw/zd_usb.c b/drivers/net/wireless/zd1211rw/zd_usb.c
index 06041cb1c422..c32a2472eb44 100644
--- a/drivers/net/wireless/zd1211rw/zd_usb.c
+++ b/drivers/net/wireless/zd1211rw/zd_usb.c
@@ -779,19 +779,20 @@ void zd_usb_disable_tx(struct zd_usb *usb)
 {
         struct zd_usb_tx *tx = &usb->tx;
         unsigned long flags;
-        struct list_head *pos, *n;
+
+        atomic_set(&tx->enabled, 0);
+
+        /* kill all submitted tx-urbs */
+        usb_kill_anchored_urbs(&tx->submitted);
 
         spin_lock_irqsave(&tx->lock, flags);
-        list_for_each_safe(pos, n, &tx->free_urb_list) {
-                list_del(pos);
-                usb_free_urb(list_entry(pos, struct urb, urb_list));
-        }
-        tx->enabled = 0;
+        WARN_ON(tx->submitted_urbs != 0);
         tx->submitted_urbs = 0;
+        spin_unlock_irqrestore(&tx->lock, flags);
+
         /* The stopped state is ignored, relying on ieee80211_wake_queues()
          * in a potentionally following zd_usb_enable_tx().
          */
-        spin_unlock_irqrestore(&tx->lock, flags);
 }
 
 /**
@@ -807,63 +808,13 @@ void zd_usb_enable_tx(struct zd_usb *usb)
         struct zd_usb_tx *tx = &usb->tx;
 
         spin_lock_irqsave(&tx->lock, flags);
-        tx->enabled = 1;
+        atomic_set(&tx->enabled, 1);
         tx->submitted_urbs = 0;
         ieee80211_wake_queues(zd_usb_to_hw(usb));
         tx->stopped = 0;
         spin_unlock_irqrestore(&tx->lock, flags);
 }
 
-/**
- * alloc_tx_urb - provides an tx URB
- * @usb: a &struct zd_usb pointer
- *
- * Allocates a new URB. If possible takes the urb from the free list in
- * usb->tx.
- */
-static struct urb *alloc_tx_urb(struct zd_usb *usb)
-{
-        struct zd_usb_tx *tx = &usb->tx;
-        unsigned long flags;
-        struct list_head *entry;
-        struct urb *urb;
-
-        spin_lock_irqsave(&tx->lock, flags);
-        if (list_empty(&tx->free_urb_list)) {
-                urb = usb_alloc_urb(0, GFP_ATOMIC);
-                goto out;
-        }
-        entry = tx->free_urb_list.next;
-        list_del(entry);
-        urb = list_entry(entry, struct urb, urb_list);
-out:
-        spin_unlock_irqrestore(&tx->lock, flags);
-        return urb;
-}
-
-/**
- * free_tx_urb - frees a used tx URB
- * @usb: a &struct zd_usb pointer
- * @urb: URB to be freed
- *
- * Frees the transmission URB, which means to put it on the free URB
- * list.
- */
-static void free_tx_urb(struct zd_usb *usb, struct urb *urb)
-{
-        struct zd_usb_tx *tx = &usb->tx;
-        unsigned long flags;
-
-        spin_lock_irqsave(&tx->lock, flags);
-        if (!tx->enabled) {
-                usb_free_urb(urb);
-                goto out;
-        }
-        list_add(&urb->urb_list, &tx->free_urb_list);
-out:
-        spin_unlock_irqrestore(&tx->lock, flags);
-}
-
 static void tx_dec_submitted_urbs(struct zd_usb *usb)
 {
         struct zd_usb_tx *tx = &usb->tx;
@@ -905,6 +856,16 @@ static void tx_urb_complete(struct urb *urb)
         struct sk_buff *skb;
         struct ieee80211_tx_info *info;
         struct zd_usb *usb;
+        struct zd_usb_tx *tx;
+
+        skb = (struct sk_buff *)urb->context;
+        info = IEEE80211_SKB_CB(skb);
+        /*
+         * grab 'usb' pointer before handing off the skb (since
+         * it might be freed by zd_mac_tx_to_dev or mac80211)
+         */
+        usb = &zd_hw_mac(info->rate_driver_data[0])->chip.usb;
+        tx = &usb->tx;
 
         switch (urb->status) {
         case 0:
@@ -922,20 +883,15 @@ static void tx_urb_complete(struct urb *urb)
                 goto resubmit;
         }
 free_urb:
-        skb = (struct sk_buff *)urb->context;
-        /*
-         * grab 'usb' pointer before handing off the skb (since
-         * it might be freed by zd_mac_tx_to_dev or mac80211)
-         */
-        info = IEEE80211_SKB_CB(skb);
-        usb = &zd_hw_mac(info->rate_driver_data[0])->chip.usb;
         zd_mac_tx_to_dev(skb, urb->status);
-        free_tx_urb(usb, urb);
+        usb_free_urb(urb);
         tx_dec_submitted_urbs(usb);
         return;
 resubmit:
+        usb_anchor_urb(urb, &tx->submitted);
         r = usb_submit_urb(urb, GFP_ATOMIC);
         if (r) {
+                usb_unanchor_urb(urb);
                 dev_dbg_f(urb_dev(urb), "error resubmit urb %p %d\n", urb, r);
                 goto free_urb;
         }
@@ -958,8 +914,14 @@ int zd_usb_tx(struct zd_usb *usb, struct sk_buff *skb)
         int r;
         struct usb_device *udev = zd_usb_to_usbdev(usb);
         struct urb *urb;
+        struct zd_usb_tx *tx = &usb->tx;
 
-        urb = alloc_tx_urb(usb);
+        if (!atomic_read(&tx->enabled)) {
+                r = -ENOENT;
+                goto out;
+        }
+
+        urb = usb_alloc_urb(0, GFP_ATOMIC);
         if (!urb) {
                 r = -ENOMEM;
                 goto out;
@@ -968,13 +930,16 @@ int zd_usb_tx(struct zd_usb *usb, struct sk_buff *skb)
         usb_fill_bulk_urb(urb, udev, usb_sndbulkpipe(udev, EP_DATA_OUT),
                           skb->data, skb->len, tx_urb_complete, skb);
 
+        usb_anchor_urb(urb, &tx->submitted);
         r = usb_submit_urb(urb, GFP_ATOMIC);
-        if (r)
+        if (r) {
+                usb_unanchor_urb(urb);
                 goto error;
+        }
         tx_inc_submitted_urbs(usb);
         return 0;
 error:
-        free_tx_urb(usb, urb);
+        usb_free_urb(urb);
 out:
         return r;
 }
@@ -1005,9 +970,9 @@ static inline void init_usb_tx(struct zd_usb *usb)
 {
         struct zd_usb_tx *tx = &usb->tx;
         spin_lock_init(&tx->lock);
-        tx->enabled = 0;
+        atomic_set(&tx->enabled, 0);
         tx->stopped = 0;
-        INIT_LIST_HEAD(&tx->free_urb_list);
+        init_usb_anchor(&tx->submitted);
         tx->submitted_urbs = 0;
 }
 
@@ -1240,6 +1205,7 @@ static void disconnect(struct usb_interface *intf)
         ieee80211_unregister_hw(hw);
 
         /* Just in case something has gone wrong! */
+        zd_usb_disable_tx(usb);
         zd_usb_disable_rx(usb);
         zd_usb_disable_int(usb);
 
diff --git a/drivers/net/wireless/zd1211rw/zd_usb.h b/drivers/net/wireless/zd1211rw/zd_usb.h
index 1b1655cb7cb4..233ce825b71c 100644
--- a/drivers/net/wireless/zd1211rw/zd_usb.h
+++ b/drivers/net/wireless/zd1211rw/zd_usb.h
@@ -184,18 +184,18 @@ struct zd_usb_rx {
 
 /**
  * struct zd_usb_tx - structure used for transmitting frames
+ * @enabled: atomic enabled flag, indicates whether tx is enabled
  * @lock: lock for transmission
- * @free_urb_list: list of free URBs, contains all the URBs, which can be used
+ * @submitted: anchor for URBs sent to device
  * @submitted_urbs: atomic integer that counts the URBs having sent to the
  *      device, which haven't been completed
- * @enabled: enabled flag, indicates whether tx is enabled
  * @stopped: indicates whether higher level tx queues are stopped
  */
 struct zd_usb_tx {
+        atomic_t enabled;
         spinlock_t lock;
-        struct list_head free_urb_list;
+        struct usb_anchor submitted;
         int submitted_urbs;
-        int enabled;
         int stopped;
 };