Re: [PATCH net 5/8] net: bcmgenet: acquire ring lock with BH disabled in bcmgenet_dump_tx_queue

[Nicolai Buchwitz <nb@tipi-net.de>]

Hi Florian

On 18.9.2026 02:07, Florian Fainelli wrote:
> bcmgenet_dump_tx_queue() is called from bcmgenet_timeout() in process 
> or
> timer context and acquires ring->lock using spin_lock(). If a softirq
> such as TX NAPI (bcmgenet_tx_poll()) fires on the same CPU while the 
> lock
> is held, it will deadlock trying to acquire ring->lock.

AFAIU bcmgenet_timeout() only runs from dev_watchdog(), so BH is already
disabled and no deadlock?

> 
> Use spin_lock_bh() and spin_unlock_bh() in bcmgenet_dump_tx_queue(),
> matching bcmgenet_tx_reclaim().
> 
> Fixes: 13ea657806cf ("net: bcmgenet: improve TX timeout")
> Assisted-by: LLM
> Co-authored-by: Cursor <cursoragent@cursor.com>
> Change-Id: I0c4c6392590b2d16abd44f75d3f6974f3e1b874b
> ---
>  drivers/net/ethernet/broadcom/genet/bcmgenet.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/broadcom/genet/bcmgenet.c 
> b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> index ef155a170fa6..799da63e3a4e 100644
> --- a/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> +++ b/drivers/net/ethernet/broadcom/genet/bcmgenet.c
> @@ -3508,14 +3508,14 @@ static void bcmgenet_dump_tx_queue(struct 
> bcmgenet_tx_ring *ring)
> 
>  	txq = netdev_get_tx_queue(priv->dev, ring->index);
> 
> -	spin_lock(&ring->lock);
> +	spin_lock_bh(&ring->lock);
>  	intsts = ~bcmgenet_intrl2_1_readl(priv, INTRL2_CPU_MASK_STATUS);
>  	intmsk = 1 << ring->index;
>  	c_index = bcmgenet_tdma_ring_readl(priv, ring->index, 
> TDMA_CONS_INDEX);
>  	p_index = bcmgenet_tdma_ring_readl(priv, ring->index, 
> TDMA_PROD_INDEX);
>  	txq_stopped = netif_tx_queue_stopped(txq);
>  	free_bds = ring->free_bds;
> -	spin_unlock(&ring->lock);
> +	spin_unlock_bh(&ring->lock);
> 
>  	netif_err(priv, tx_err, priv->dev, "Ring %d queue %d status 
> summary\n"
>  		  "TX queue status: %s, interrupts: %s\n"

Regards,
Nicolai