Re: [PATCH net v3 2/2] net: stmmac: Stop Tx queue when (en|dis)abling XSK pools

Hi Kurt

On 13.10.2026 10:57, Kurt Kanzenbach wrote:

When enabling or disabling XSK pools in parallel to Tx traffic, kernel
crashes occur. For VLAN tagged frames that happens in stmmac_xmit() ->
dwmac4_set_vlan_tag() and for normal frames in stmmac_xmit() ->
dwmac4_set_addr(). Both of these functions access the Tx DMA descriptors.

The XDP pool (en|dis)ablement frees and reallocates the Tx DMA resources:

 stmmac_disable_tx_queue:
   __free_dma_tx_desc_resources

 stmmac_enable_tx_queue:
   __alloc_dma_tx_desc_resources
   __init_dma_tx_desc_rings

NAPI is disabled during that allocation window, but the Tx queue is not
stopped. Therefore, add the stopping of the Tx queue during the enabling
and disabling of XSK pools.

The issue can be easily reproduced by:

 1. Run iperf
 2. Run application which opens an AF_XDP/ZC socket

Also add a dedicated queue check for the XDP Tx paths.

Fixes: 132c32ee5bc0 ("net: stmmac: Add TX via XDP zero-copy socket")
Suggested-by: Nicolai Buchwitz <nb@tipi-net.de> # XDP Tx checks
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>

[...]

Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Tested-by: Nicolai Buchwitz <nb@tipi-net.de> # stm32mp215

Thanks,
Nicolai