2019-03-25 19:18:51

by Lorenzo Bianconi

Subject: [PATCH v2] mt76: usb: reduce locking in mt76u_tx_tasklet

Similar to pci counterpart, reduce locking in mt76u_tx_tasklet since
q->head is managed just in mt76u_tx_tasklet and q->queued is updated
holding q->lock

Signed-off-by: Lorenzo Bianconi <[email protected]>
---
Changes since v1:
- drop idx variable
Changes since RFC:
- reset done to false in mt76u_tx_tasklet instead of in mt76u_tx_queue_skb
This patch is based on https://patchwork.kernel.org/patch/10856027/
---
drivers/net/wireless/mediatek/mt76/usb.c | 20 ++++++++++++--------
1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/mediatek/mt76/usb.c b/drivers/net/wireless/mediatek/mt76/usb.c
index 15aeda0582e7..fb8b22c1655a 100644
--- a/drivers/net/wireless/mediatek/mt76/usb.c
+++ b/drivers/net/wireless/mediatek/mt76/usb.c
@@ -624,28 +624,33 @@ static void mt76u_tx_tasklet(unsigned long data)
int i;

for (i = 0; i < IEEE80211_NUM_ACS; i++) {
+ u32 n_dequeued = 0, n_sw_dequeued = 0;
+
sq = &dev->q_tx[i];
q = sq->q;

- spin_lock_bh(&q->lock);
- while (true) {
- if (!q->entry[q->head].done || !q->queued)
+ while (q->queued > n_dequeued) {
+ if (!q->entry[q->head].done)
break;

if (q->entry[q->head].schedule) {
q->entry[q->head].schedule = false;
- sq->swq_queued--;
+ n_sw_dequeued++;
}

entry = q->entry[q->head];
+ q->entry[q->head].done = false;
q->head = (q->head + 1) % q->ndesc;
- q->queued--;
+ n_dequeued++;

- spin_unlock_bh(&q->lock);
dev->drv->tx_complete_skb(dev, i, &entry);
- spin_lock_bh(&q->lock);
}

+ spin_lock_bh(&q->lock);
+
+ sq->swq_queued -= n_sw_dequeued;
+ q->queued -= n_dequeued;
+
wake = q->stopped && q->queued < q->ndesc - 8;
if (wake)
q->stopped = false;
@@ -741,7 +746,6 @@ mt76u_tx_queue_skb(struct mt76_dev *dev, enum mt76_txq_id qid,
if (err < 0)
return err;

- q->entry[idx].done = false;
urb = q->entry[idx].urb;
err = mt76u_tx_setup_buffers(dev, skb, urb);
if (err < 0)
--
2.20.1

2019-04-25 12:48:15

by Felix Fietkau

Subject: Re: [PATCH v2] mt76: usb: reduce locking in mt76u_tx_tasklet

On 2019-03-25 20:18, Lorenzo Bianconi wrote:
> Similar to pci counterpart, reduce locking in mt76u_tx_tasklet since
> q->head is managed just in mt76u_tx_tasklet and q->queued is updated
> holding q->lock
>
> Signed-off-by: Lorenzo Bianconi <[email protected]>
Applied, thanks.

- Felix