On 06.07.24 10:38, Ronald Wahl wrote:
On 06.07.24 02:39, Jakub Kicinski wrote:
On Thu, 4 Jul 2024 19:47:56 +0200 Ronald Wahl wrote:
--- a/drivers/net/ethernet/micrel/ks8851_spi.c +++ b/drivers/net/ethernet/micrel/ks8851_spi.c @@ -385,7 +385,7 @@ static netdev_tx_t ks8851_start_xmit_spi(struct sk_buff *skb, netif_dbg(ks, tx_queued, ks->netdev, "%s: skb %p, %d@%p\n", __func__, skb, skb->len, skb->data);
- spin_lock(&ks->statelock);
spin_lock_bh(&ks->statelock);
if (ks->queued_len + needed > ks->tx_space) { netif_stop_queue(dev);
@@ -395,7 +395,7 @@ static netdev_tx_t ks8851_start_xmit_spi(struct sk_buff *skb, skb_queue_tail(&ks->txq, skb); }
- spin_unlock(&ks->statelock);
- spin_unlock_bh(&ks->statelock);
this one probably can stay as spin_lock() since networking stack only calls xmit in BH context.
I already suspected this it was more a mental hint here. I will remove it.
But I see 2 other spin_lock(statelock) in the driver which I'm not as sure about. Any taking of this lock has to be _bh() unless you're sure the caller is already in BH.
The other two instances are not in BH context as far as I know but also do not interfere with BH. The one in ks8861_tx_work protects only variable assignments used only inside the driver and the one in ks8851_set_rx_mode also only does some driver local variable stuff and a schedule_work which as far as I know has nothing to do with BH because workqueues are running in process context. Am I wrong here?
I guess I found a misunderstanding on my side: I was assuming that a softirq cannot asynchronously interrupt a spin lock protected section. Maybe this is wrong. In the one place where I'm waking the queue again the spin_lock_bh avoids synchronously triggering the BH processing while still holding a spinlock.
I will use the _bh variants on the two other places. - ron
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