Re: [PATCH] net: airoha: Clean up RX queues in airoha_dev_stop

[Simon Horman <horms@kernel.org>]

On Tue, Jun 16, 2026 at 06:50:48PM +0800, Wayen Yan wrote:
> When the last port is stopped, airoha_dev_stop() clears TX queues
> but neglects to clean up RX queues. This can lead to:
> - RX ring buffer descriptors remaining valid after device close
> - Potential DMA synchronization issues on device reopen
> - Risk of use-after-free if pages are freed while DMA is still active
> 
> Add cleanup loop for RX queues to mirror the TX queue cleanup,
> ensuring symmetric resource management.
> 
> Fixes: 20bf7d07c956 ("net: airoha: add QDMA support for Airoha EN7581 Ethernet")
> Signed-off-by: Wayen Yan <win847@gmail.com>

Hi Wayen Yan,

There is AI-generated review of this patch-set available on both
https://sashiko.dev and https://netdev-ai.bots.linux.dev/sashiko/

I asked AI to summarise these concerns, it came up with the
following. I would appreciate it if you could look over this feedback.

1. NAPI Synchronization:
   While the TX path is managed by the netdev layer during stop, the RX path
   relies on the NAPI subsystem. Since NAPI remains active during
   `airoha_dev_stop()`, the new cleanup loop could race with the poller
   (`airoha_qdma_rx_process`). It would be safer to call `napi_disable()`
   before draining the queues to ensure exclusive access to the descriptors.

2. RX Queue Refill:
   Unlike TX, the RX hardware requires descriptors to be pre-allocated and
   posted by the driver to receive data. Because this patch empties the rings,
   `airoha_dev_open()` needs a corresponding update to refill them (e.g.,
   via `airoha_qdma_fill_rx_queue()`). Without this, the interface will
   encounter an empty ring on restart, leading to an RX stall.

3. SKB Accumulation:
   The cleanup should also account for the `q->skb` pointer used for
   fragmented packets. If a partial packet is sitting in the queue when the
   interface is stopped, freeing it and resetting the pointer to NULL will
   prevent a memory leak and ensure the next session starts with a clean
   state.