Subject: Re: [PATCH net-next v2] net: mana: Implement ndo_tx_timeout and serialize queue resets per port.

From: Jakub Kicinski <[email-masked]>
Date: Wed, 29 Oct 2025 18:22:33 -0700

On Mon, 27 Oct 2025 13:13:51 -0700 Dipayaan Roy wrote:
> Implement .ndo_tx_timeout for MANA so any stalled TX queue can be detected
> and a device-controlled port reset for all queues can be scheduled to a
> ordered workqueue. The reset for all queues on stall detection is
> recomended by hardware team.
> 
> The change introduces a single ordered workqueue
> ("mana_per_port_queue_reset_wq") with WQ_UNBOUND | WQ_MEM_RECLAIM and
> queues exactly one work_struct per port onto it. This achieves:
> 
>   * Global FIFO across all port reset requests (alloc_ordered_workqueue).

Why does this matter?

>   * Natural per-port de-duplication: the same work_struct cannot be
>     queued twice while pending/running.

That's true for all work_structs even without a separate wq.

>   * Avoids hogging a per-CPU kworker for long, may-sleep reset paths
>     (WQ_UNBOUND).

?

>   * Guarantees forward progress during memory pressure
>     (WQ_MEM_RECLAIM rescuer).

? meaning? What scenario are you preventing?

> Reviewed-by: Haiyang Zhang <[email-masked]>
> Signed-off-by: Dipayaan Roy <[email-masked]>
> ---
> Changes in v2:
>   - Fixed cosmetic changes.
> ---
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 82 +++++++++++++++++++
>  include/net/mana/gdma.h                       |  6 +-
>  include/net/mana/mana.h                       | 15 ++++
>  3 files changed, 102 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index f4fc86f20213..05b7046ae3b5 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -258,6 +258,45 @@ static int mana_get_gso_hs(struct sk_buff *skb)
>  	return gso_hs;
>  }
>  
> +static void mana_per_port_queue_reset_work_handler(struct work_struct *work)
> +{
> +	struct mana_queue_reset_work *reset_queue_work =
> +			container_of(work, struct mana_queue_reset_work, work);
> +	struct mana_port_context *apc = reset_queue_work->apc;
> +	struct net_device *ndev = apc->ndev;
> +	struct mana_context *ac = apc->ac;
> +	int err;
> +
> +	if (!rtnl_trylock()) {

Use disable_work_sync() in the remove path and you won't have to do 
the retry dance, right?

> +		/* Someone else holds RTNL, requeue and exit. */
> +		queue_work(ac->per_port_queue_reset_wq,
> +			   &apc->queue_reset_work.work);
> +		return;
> +	}

> +static void mana_tx_timeout(struct net_device *netdev, unsigned int txqueue)
> +{
> +	struct mana_port_context *apc = netdev_priv(netdev);
> +	struct mana_context *ac = apc->ac;
> +	struct gdma_context *gc = ac->gdma_dev->gdma_context;
> +
> +	netdev_warn(netdev, "%s(): called on txq: %u\n", __func__, txqueue);

I believe that core already prints this sort of thing, please don't
duplicate.

> +	/* Already in service, hence tx queue reset is not required.*/
> +	if (gc->in_service)
> +		return;
> +
> +	/* Note: If there are pending queue reset work for this port(apc),
> +	 * subsequent request queued up from here are ignored. This is because
> +	 * we are using the same work instance per port(apc).
> +	 */
> +	queue_work(ac->per_port_queue_reset_wq, &apc->queue_reset_work.work);
> +}
> +
>  static int mana_shaper_set(struct net_shaper_binding *binding,
>  			   const struct net_shaper *shaper,
>  			   struct netlink_ext_ack *extack)
> @@ -844,7 +902,9 @@ static const struct net_device_ops mana_devops = {
>  	.ndo_bpf		= mana_bpf,
>  	.ndo_xdp_xmit		= mana_xdp_xmit,
>  	.ndo_change_mtu		= mana_change_mtu,
> +	.ndo_tx_timeout     = mana_tx_timeout,

other ndos were aligned with tabs you're using spaces

>  	.net_shaper_ops         = &mana_shaper_ops,
> +
>  };
>  
>  static void mana_cleanup_port_context(struct mana_port_context *apc)
> @@ -3218,6 +3278,7 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
>  	ndev->min_mtu = ETH_MIN_MTU;
>  	ndev->needed_headroom = MANA_HEADROOM;
>  	ndev->dev_port = port_idx;
> +	ndev->watchdog_timeo = MANA_TXQ_TIMEOUT;

why you need a define for this is unclear. You can use 15 * HZ here
directly 

>  	SET_NETDEV_DEV(ndev, gc->dev);
>  
>  	netif_set_tso_max_size(ndev, GSO_MAX_SIZE);
> @@ -3255,6 +3316,11 @@ static int mana_probe_port(struct mana_context *ac, int port_idx,
>  
>  	debugfs_create_u32("current_speed", 0400, apc->mana_port_debugfs, &apc->speed);
>  
> +	/* Initialize the per port queue reset work.*/
> +	apc->queue_reset_work.apc = apc;
> +	INIT_WORK(&apc->queue_reset_work.work,
> +		  mana_per_port_queue_reset_work_handler);
> +
>  	return 0;
>  
>  free_indir:
> @@ -3456,6 +3522,15 @@ int mana_probe(struct gdma_dev *gd, bool resuming)
>  	if (ac->num_ports > MAX_PORTS_IN_MANA_DEV)
>  		ac->num_ports = MAX_PORTS_IN_MANA_DEV;
>  
> +	ac->per_port_queue_reset_wq =
> +			alloc_ordered_workqueue("mana_per_port_queue_reset_wq",
> +						WQ_UNBOUND | WQ_MEM_RECLAIM);
> +	if (!ac->per_port_queue_reset_wq) {
> +		dev_err(dev, "Failed to allocate per port queue reset workqueue\n");
> +		err = -ENOMEM;
> +		goto out;
> +	}
> +
>  	if (!resuming) {
>  		for (i = 0; i < ac->num_ports; i++) {
>  			err = mana_probe_port(ac, i, &ac->ports[i]);
> @@ -3528,6 +3603,8 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
>  		 */
>  		rtnl_lock();
>  
> +		cancel_work_sync(&apc->queue_reset_work.work);
> +
>  		err = mana_detach(ndev, false);
>  		if (err)
>  			netdev_err(ndev, "Failed to detach vPort %d: %d\n",
> @@ -3547,6 +3624,11 @@ void mana_remove(struct gdma_dev *gd, bool suspending)
>  		free_netdev(ndev);
>  	}
>  
> +	if (ac->per_port_queue_reset_wq) {
> +		destroy_workqueue(ac->per_port_queue_reset_wq);
> +		ac->per_port_queue_reset_wq = NULL;
> +	}
> +
>  	mana_destroy_eq(ac);
>  out:
>  	mana_gd_deregister_device(gd);
> diff --git a/include/net/mana/gdma.h b/include/net/mana/gdma.h
> index 57df78cfbf82..1f8c536ba3be 100644
> --- a/include/net/mana/gdma.h
> +++ b/include/net/mana/gdma.h
> @@ -591,6 +591,9 @@ enum {
>  /* Driver can self reset on FPGA Reconfig EQE notification */
>  #define GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE BIT(17)
>  
> +/* Driver detects stalled send queues and recovers them */
> +#define GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY BIT(18)
> +
>  #define GDMA_DRV_CAP_FLAGS1 \
>  	(GDMA_DRV_CAP_FLAG_1_EQ_SHARING_MULTI_VPORT | \
>  	 GDMA_DRV_CAP_FLAG_1_NAPI_WKDONE_FIX | \
> @@ -599,7 +602,8 @@ enum {
>  	 GDMA_DRV_CAP_FLAG_1_DEV_LIST_HOLES_SUP | \
>  	 GDMA_DRV_CAP_FLAG_1_DYNAMIC_IRQ_ALLOC_SUPPORT | \
>  	 GDMA_DRV_CAP_FLAG_1_SELF_RESET_ON_EQE | \
> -	 GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE)
> +	 GDMA_DRV_CAP_FLAG_1_HANDLE_RECONFIG_EQE | \
> +	 GDMA_DRV_CAP_FLAG_1_HANDLE_STALL_SQ_RECOVERY)
>  
>  #define GDMA_DRV_CAP_FLAGS2 0
>  
> diff --git a/include/net/mana/mana.h b/include/net/mana/mana.h
> index 0921485565c0..e0b44ae2226a 100644
> --- a/include/net/mana/mana.h
> +++ b/include/net/mana/mana.h
> @@ -67,6 +67,11 @@ enum TRI_STATE {
>  
>  #define MANA_RX_FRAG_ALIGNMENT 64
>  
> +/* Timeout value for Txq stall detection & recovery used by ndo_tx_timeout.
> + * The value is chosen after considering fpga re-config scenarios.
> + */
> +#define MANA_TXQ_TIMEOUT (15 * HZ)
> +
>  struct mana_stats_rx {
>  	u64 packets;
>  	u64 bytes;
> @@ -475,13 +480,23 @@ struct mana_context {
>  
>  	struct mana_eq *eqs;
>  	struct dentry *mana_eqs_debugfs;
> +	struct workqueue_struct *per_port_queue_reset_wq;
>  
>  	struct net_device *ports[MAX_PORTS_IN_MANA_DEV];
>  };
>  
> +struct mana_queue_reset_work {
> +

nit spurious empty line

> +	/* Work structure */
> +	struct work_struct work;
> +	/* Pointer to the port context */
> +	struct mana_port_context *apc;

This struct is placed in apc, unclear why you need a backpointer
instead of using container_of()

> +};
> +
>  struct mana_port_context {
>  	struct mana_context *ac;
>  	struct net_device *ndev;
> +	struct mana_queue_reset_work queue_reset_work;
>  
>  	u8 mac_addr[ETH_ALEN];
>  

-- 
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