[PATCH net V4] veth: more robust handing of race to avoid txq getting stuck

[patchwork-bot+netdevbpf at kernel.org]

Hello:

This patch was applied to netdev/net.git (main)
by Jakub Kicinski <kuba at kernel.org>:

On Wed, 12 Nov 2025 14:13:52 +0100 you wrote:
> Commit dc82a33297fc ("veth: apply qdisc backpressure on full ptr_ring to
> reduce TX drops") introduced a race condition that can lead to a permanently
> stalled TXQ. This was observed in production on ARM64 systems (Ampere Altra
> Max).
> 
> The race occurs in veth_xmit(). The producer observes a full ptr_ring and
> stops the queue (netif_tx_stop_queue()). The subsequent conditional logic,
> intended to re-wake the queue if the consumer had just emptied it (if
> (__ptr_ring_empty(...)) netif_tx_wake_queue()), can fail. This leads to a
> "lost wakeup" where the TXQ remains stopped (QUEUE_STATE_DRV_XOFF) and
> traffic halts.
> 
> [...]

Here is the summary with links:
  - [net,V4] veth: more robust handing of race to avoid txq getting stuck
    https://git.kernel.org/netdev/net/c/5442a9da6978

You are awesome, thank you!
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