Re: [PATCH net-next v7 03/10] net: airoha: Move airoha_qdma pointer in airoha_gdm_dev struct

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] Deadlock risk due to using `spin_lock` instead of `spin_lock_bh` in `airoha_update_hw_stats`.
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commit af5b93ea60b28ce8a1ab1016b0911418480e766a
Author: Lorenzo Bianconi <lorenzo@kernel.org>

net: airoha: Move airoha_qdma pointer in airoha_gdm_dev struct

This commit moves the airoha_qdma pointer from the airoha_gdm_port
struct to airoha_gdm_dev, since the QDMA block depends on the net_device
configuration. This is a preliminary patch to support multiple
net_devices connected to the same port via an external hardware arbiter.

> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 3ca0dbd19275a..6c9f4b289dba7 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
[ ... ]
> @@ -1560,9 +1564,10 @@ static void airoha_qdma_stop_napi(struct airoha_qdma *qdma)
>  	}
>  }
>  
> -static void airoha_update_hw_stats(struct airoha_gdm_port *port)
> +static void airoha_update_hw_stats(struct airoha_gdm_dev *dev)
>  {
> -	struct airoha_eth *eth = port->qdma->eth;
> +	struct airoha_gdm_port *port = dev->port;
> +	struct airoha_eth *eth = dev->eth;
>  	u32 val, i = 0;
>  
>  	spin_lock(&port->stats.lock);

This isn't a regression introduced by this patch, but does this spin_lock()
need to use the _bh variant to prevent a deadlock?

This function is called from ethtool paths like airoha_ethtool_get_mac_stats()
and airoha_ethtool_get_rmon_stats(), which run in process context. It is also
called from airoha_dev_get_stats64() via ndo_get_stats64, which can be invoked
from softirq context when queried by a bridging or bonding master or qdisc in
the TX/RX paths.

If a process-context ethtool operation is preempted by a softirq on the same
CPU that then invokes dev_get_stats(), could the softirq attempt to acquire
the already-held port->stats.lock and cause a deadlock?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260516-airoha-eth-multi-serdes-v7-0-99e0093303e2@kernel.org?part=3