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wifi: mt76: fix race condition related to checking tx queue fill status
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When drv_tx calls race against local tx scheduling, the queue fill status checks
can potentially race, leading to dma queue entries being overwritten.
Fix this by deferring packets from drv_tx calls to the tx worker, in order to
ensure that all regular queue tx comes from the same context.

Signed-off-by: Felix Fietkau <[email protected]>
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@nbd168
nbd168 committed Sep 11, 2023
1 parent bbbac7d commit f1e1e67
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Showing 3 changed files with 120 additions and 20 deletions.
27 changes: 27 additions & 0 deletions mac80211.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -416,6 +416,9 @@ mt76_phy_init(struct mt76_phy *phy, struct ieee80211_hw *hw)
struct mt76_dev *dev = phy->dev;
struct wiphy *wiphy = hw->wiphy;

INIT_LIST_HEAD(&phy->tx_list);
spin_lock_init(&phy->tx_lock);

SET_IEEE80211_DEV(hw, dev->dev);
SET_IEEE80211_PERM_ADDR(hw, phy->macaddr);

Expand Down Expand Up @@ -690,6 +693,7 @@ int mt76_register_device(struct mt76_dev *dev, bool vht,
int ret;

dev_set_drvdata(dev->dev, dev);
mt76_wcid_init(&dev->global_wcid);
ret = mt76_phy_init(phy, hw);
if (ret)
return ret;
Expand Down Expand Up @@ -745,6 +749,7 @@ void mt76_unregister_device(struct mt76_dev *dev)
if (IS_ENABLED(CONFIG_MT76_LEDS))
mt76_led_cleanup(&dev->phy);
mt76_tx_status_check(dev, true);
mt76_wcid_cleanup(dev, &dev->global_wcid);
ieee80211_unregister_hw(hw);
}
EXPORT_SYMBOL_GPL(mt76_unregister_device);
Expand Down Expand Up @@ -1485,20 +1490,42 @@ EXPORT_SYMBOL_GPL(mt76_sta_pre_rcu_remove);

void mt76_wcid_init(struct mt76_wcid *wcid)
{
INIT_LIST_HEAD(&wcid->tx_list);
skb_queue_head_init(&wcid->tx_pending);

INIT_LIST_HEAD(&wcid->list);
idr_init(&wcid->pktid);
}
EXPORT_SYMBOL_GPL(mt76_wcid_init);

void mt76_wcid_cleanup(struct mt76_dev *dev, struct mt76_wcid *wcid)
{
struct mt76_phy *phy = dev->phys[wcid->phy_idx];
struct ieee80211_hw *hw;
struct sk_buff_head list;
struct sk_buff *skb;

mt76_tx_status_lock(dev, &list);
mt76_tx_status_skb_get(dev, wcid, -1, &list);
mt76_tx_status_unlock(dev, &list);

idr_destroy(&wcid->pktid);

spin_lock_bh(&phy->tx_lock);

if (!list_empty(&wcid->tx_list))
list_del_init(&wcid->tx_list);

spin_lock(&wcid->tx_pending.lock);
skb_queue_splice_tail_init(&wcid->tx_pending, &list);
spin_unlock(&wcid->tx_pending.lock);

spin_unlock_bh(&phy->tx_lock);

while ((skb = __skb_dequeue(&list)) != NULL) {
hw = mt76_tx_status_get_hw(dev, skb);
ieee80211_free_txskb(hw, skb);
}
}
EXPORT_SYMBOL_GPL(mt76_wcid_cleanup);

Expand Down
5 changes: 5 additions & 0 deletions mt76.h
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Original file line number Diff line number Diff line change
Expand Up @@ -333,6 +333,9 @@ struct mt76_wcid {
u32 tx_info;
bool sw_iv;

struct list_head tx_list;
struct sk_buff_head tx_pending;

struct list_head list;
struct idr pktid;

Expand Down Expand Up @@ -708,6 +711,8 @@ struct mt76_phy {
unsigned long state;
u8 band_idx;

spinlock_t tx_lock;
struct list_head tx_list;
struct mt76_queue *q_tx[__MT_TXQ_MAX];

struct cfg80211_chan_def chandef;
Expand Down
108 changes: 88 additions & 20 deletions tx.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -329,40 +329,32 @@ void
mt76_tx(struct mt76_phy *phy, struct ieee80211_sta *sta,
struct mt76_wcid *wcid, struct sk_buff *skb)
{
struct mt76_dev *dev = phy->dev;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
struct mt76_queue *q;
int qid = skb_get_queue_mapping(skb);

if (mt76_testmode_enabled(phy)) {
ieee80211_free_txskb(phy->hw, skb);
return;
}

if (WARN_ON(qid >= MT_TXQ_PSD)) {
qid = MT_TXQ_BE;
skb_set_queue_mapping(skb, qid);
}

if ((dev->drv->drv_flags & MT_DRV_HW_MGMT_TXQ) &&
!(info->flags & IEEE80211_TX_CTL_HW_80211_ENCAP) &&
!ieee80211_is_data(hdr->frame_control) &&
!ieee80211_is_bufferable_mmpdu(skb)) {
qid = MT_TXQ_PSD;
}
if (WARN_ON(skb_get_queue_mapping(skb) >= MT_TXQ_PSD))
skb_set_queue_mapping(skb, MT_TXQ_BE);

if (wcid && !(wcid->tx_info & MT_WCID_TX_INFO_SET))
ieee80211_get_tx_rates(info->control.vif, sta, skb,
info->control.rates, 1);

info->hw_queue |= FIELD_PREP(MT_TX_HW_QUEUE_PHY, phy->band_idx);
q = phy->q_tx[qid];

spin_lock_bh(&q->lock);
__mt76_tx_queue_skb(phy, qid, skb, wcid, sta, NULL);
dev->queue_ops->kick(dev, q);
spin_unlock_bh(&q->lock);
spin_lock_bh(&wcid->tx_pending.lock);
__skb_queue_tail(&wcid->tx_pending, skb);
spin_unlock_bh(&wcid->tx_pending.lock);

spin_lock_bh(&phy->tx_lock);
if (list_empty(&wcid->tx_list))
list_add_tail(&wcid->tx_list, &phy->tx_list);
spin_unlock_bh(&phy->tx_lock);

mt76_worker_schedule(&phy->dev->tx_worker);
}
EXPORT_SYMBOL_GPL(mt76_tx);

Expand Down Expand Up @@ -593,10 +585,86 @@ void mt76_txq_schedule(struct mt76_phy *phy, enum mt76_txq_id qid)
}
EXPORT_SYMBOL_GPL(mt76_txq_schedule);

static int
mt76_txq_schedule_pending_wcid(struct mt76_phy *phy, struct mt76_wcid *wcid)
{
struct mt76_dev *dev = phy->dev;
struct ieee80211_sta *sta;
struct mt76_queue *q;
struct sk_buff *skb;
int ret = 0;

spin_lock(&wcid->tx_pending.lock);
while ((skb = skb_peek(&wcid->tx_pending)) != NULL) {
struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
int qid = skb_get_queue_mapping(skb);

if ((dev->drv->drv_flags & MT_DRV_HW_MGMT_TXQ) &&
!(info->flags & IEEE80211_TX_CTL_HW_80211_ENCAP) &&
!ieee80211_is_data(hdr->frame_control) &&
!ieee80211_is_bufferable_mmpdu(skb))
qid = MT_TXQ_PSD;

q = phy->q_tx[qid];
if (mt76_txq_stopped(q)) {
ret = -1;
break;
}

__skb_unlink(skb, &wcid->tx_pending);
spin_unlock(&wcid->tx_pending.lock);

sta = wcid_to_sta(wcid);
spin_lock(&q->lock);
__mt76_tx_queue_skb(phy, qid, skb, wcid, sta, NULL);
dev->queue_ops->kick(dev, q);
spin_unlock(&q->lock);

spin_lock(&wcid->tx_pending.lock);
}
spin_unlock(&wcid->tx_pending.lock);

return ret;
}

static void mt76_txq_schedule_pending(struct mt76_phy *phy)
{
if (list_empty(&phy->tx_list))
return;

local_bh_disable();
rcu_read_lock();

spin_lock(&phy->tx_lock);
while (!list_empty(&phy->tx_list)) {
struct mt76_wcid *wcid = NULL;
int ret;

wcid = list_first_entry(&phy->tx_list, struct mt76_wcid, tx_list);
list_del_init(&wcid->tx_list);

spin_unlock(&phy->tx_lock);
ret = mt76_txq_schedule_pending_wcid(phy, wcid);
spin_lock(&phy->tx_lock);

if (ret) {
if (list_empty(&wcid->tx_list))
list_add_tail(&wcid->tx_list, &phy->tx_list);
break;
}
}
spin_unlock(&phy->tx_lock);

rcu_read_unlock();
local_bh_enable();
}

void mt76_txq_schedule_all(struct mt76_phy *phy)
{
int i;

mt76_txq_schedule_pending(phy);
for (i = 0; i <= MT_TXQ_BK; i++)
mt76_txq_schedule(phy, i);
}
Expand Down

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