Re: [PATCH] IPoIB: serialize changing on tx_outstanding

[Leon Romanovsky <leon-2ukJVAZIZ/Y@public.gmane.org>]

On Mon, Sep 28, 2015 at 01:42:10PM +0800, Wengang Wang wrote:
> The changing on tx_outstanding should be protected by spinlock or to be
> atomic operations.
> 
> Such log is found in dmesg:
> 
> Sep 16 14:20:53 naep11x06 kernel: ib0: queue stopped 1, tx_head 1034733, tx_tail 1034733, tx_outstanding 359 ipoib_sendq_size: 512
> Sep 16 14:21:33 naep11x06 kernel: ib0: transmit timeout: latency 9560 msecs
> Sep 16 14:21:33 naep11x06 kernel: ib0: queue stopped 1, tx_head 1034854, tx_tail 1034854, tx_outstanding 511 ipoib_sendq_size: 512
> Sep 16 14:21:38 naep11x06 kernel: ib0: transmit timeout: latency 14568 msecs
> Sep 16 14:21:38 naep11x06 kernel: ib0: queue stopped 1, tx_head 1034854, tx_tail 1034854, tx_outstanding 511 ipoib_sendq_size: 512
> 
> And the send queue of ib0 kept full. When transmit timeout is reported,
> queue is reported as "stopped", but the IPoIB stuff tx_head and tx_tail
> points to same value. I am not able to see such numbers in ipoib_cm_tx
> (for CM) because I have no vmcore. Though I am not quite sure it's caused
> by parallel access of tx_outstanding(send path VS interrup path), we really
> need to serialize the changeing on tx_outstanding.
> 
> This patch also make sure the increase of tx_outstanding prior to the
> calling of post_send to avoid the possible decreasing before increasing in
> case the running of increasing is scheduled later than the interrupt
> handler.
> 
> Signed-off-by: Wengang Wang <wen.gang.wang-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
> ---
>  drivers/infiniband/ulp/ipoib/ipoib_cm.c | 40 +++++++++++++++++++++++----------
>  drivers/infiniband/ulp/ipoib/ipoib_ib.c | 24 ++++++++++++++++++--
>  2 files changed, 50 insertions(+), 14 deletions(-)
> 
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_cm.c b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> index c78dc16..044da94 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_cm.c
> @@ -710,6 +710,7 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
>  	struct ipoib_dev_priv *priv = netdev_priv(dev);
>  	struct ipoib_tx_buf *tx_req;
>  	int rc;
> +	unsigned long flags;
>  
>  	if (unlikely(skb->len > tx->mtu)) {
>  		ipoib_warn(priv, "packet len %d (> %d) too long to send, dropping\n",
> @@ -742,27 +743,36 @@ void ipoib_cm_send(struct net_device *dev, struct sk_buff *skb, struct ipoib_cm_
>  	skb_orphan(skb);
>  	skb_dst_drop(skb);
>  
> +	spin_lock_irqsave(&priv->lock, flags);
> +	if (++priv->tx_outstanding == ipoib_sendq_size) {
> +		ipoib_dbg(priv, "TX ring 0x%x full, stopping kernel net queue\n",
> +			  tx->qp->qp_num);
> +		netif_stop_queue(dev);
> +	}
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +	if (netif_queue_stopped(dev)) {
> +		rc = ib_req_notify_cq(priv->send_cq,
> +			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
> +		if (rc < 0)
> +			ipoib_warn(priv, "request notify on send CQ failed\n");
> +		else if (rc)
> +			ipoib_send_comp_handler(priv->send_cq, dev);
> +	}
> +
>  	rc = post_send(priv, tx, tx->tx_head & (ipoib_sendq_size - 1), tx_req);
>  	if (unlikely(rc)) {
>  		ipoib_warn(priv, "post_send failed, error %d\n", rc);
>  		++dev->stats.tx_errors;
> +		spin_lock_irqsave(&priv->lock, flags);
> +		--priv->tx_outstanding;
> +		if (netif_queue_stopped(dev))
> +			netif_wake_queue(dev);
> +		spin_unlock_irqrestore(&priv->lock, flags);
Why are you locking the netif_* calls?
>  		ipoib_dma_unmap_tx(priv, tx_req);
>  		dev_kfree_skb_any(skb);
>  	} else {
>  		dev->trans_start = jiffies;
>  		++tx->tx_head;
> -
> -		if (++priv->tx_outstanding == ipoib_sendq_size) {
> -			ipoib_dbg(priv, "TX ring 0x%x full, stopping kernel net queue\n",
> -				  tx->qp->qp_num);
> -			netif_stop_queue(dev);
> -			rc = ib_req_notify_cq(priv->send_cq,
> -				IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
> -			if (rc < 0)
> -				ipoib_warn(priv, "request notify on send CQ failed\n");
> -			else if (rc)
> -				ipoib_send_comp_handler(priv->send_cq, dev);
> -		}
>  	}
>  }
>  
> @@ -796,10 +806,13 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
>  	netif_tx_lock(dev);
>  
>  	++tx->tx_tail;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
>  	if (unlikely(--priv->tx_outstanding == ipoib_sendq_size >> 1) &&
>  	    netif_queue_stopped(dev) &&
>  	    test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
>  		netif_wake_queue(dev);
> +	spin_unlock_irqrestore(&priv->lock, flags);
>  
>  	if (wc->status != IB_WC_SUCCESS &&
>  	    wc->status != IB_WC_WR_FLUSH_ERR) {
> @@ -1169,6 +1182,7 @@ static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
>  	struct ipoib_dev_priv *priv = netdev_priv(p->dev);
>  	struct ipoib_tx_buf *tx_req;
>  	unsigned long begin;
> +	unsigned long flags;
>  
>  	ipoib_dbg(priv, "Destroy active connection 0x%x head 0x%x tail 0x%x\n",
>  		  p->qp ? p->qp->qp_num : 0, p->tx_head, p->tx_tail);
> @@ -1198,10 +1212,12 @@ timeout:
>  		dev_kfree_skb_any(tx_req->skb);
>  		++p->tx_tail;
>  		netif_tx_lock_bh(p->dev);
> +		spin_lock_irqsave(&priv->lock, flags);
>  		if (unlikely(--priv->tx_outstanding == ipoib_sendq_size >> 1) &&
>  		    netif_queue_stopped(p->dev) &&
>  		    test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
>  			netif_wake_queue(p->dev);
> +		spin_unlock_irqrestore(&priv->lock, flags);
>  		netif_tx_unlock_bh(p->dev);
>  	}
>  
> diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> index d266667..7616e3c 100644
> --- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> +++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
> @@ -377,6 +377,7 @@ static void ipoib_ib_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
>  	struct ipoib_dev_priv *priv = netdev_priv(dev);
>  	unsigned int wr_id = wc->wr_id;
>  	struct ipoib_tx_buf *tx_req;
> +	unsigned long flags;
>  
>  	ipoib_dbg_data(priv, "send completion: id %d, status: %d\n",
>  		       wr_id, wc->status);
> @@ -397,10 +398,13 @@ static void ipoib_ib_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
>  	dev_kfree_skb_any(tx_req->skb);
>  
>  	++priv->tx_tail;
> +
> +	spin_lock_irqsave(&priv->lock, flags);
>  	if (unlikely(--priv->tx_outstanding == ipoib_sendq_size >> 1) &&
>  	    netif_queue_stopped(dev) &&
>  	    test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
>  		netif_wake_queue(dev);
> +	spin_unlock_irqrestore(&priv->lock, flags);
>  
>  	if (wc->status != IB_WC_SUCCESS &&
>  	    wc->status != IB_WC_WR_FLUSH_ERR) {
> @@ -540,6 +544,7 @@ void ipoib_send(struct net_device *dev, struct sk_buff *skb,
>  	struct ipoib_tx_buf *tx_req;
>  	int hlen, rc;
>  	void *phead;
> +	unsigned long flags;
>  
>  	if (skb_is_gso(skb)) {
>  		hlen = skb_transport_offset(skb) + tcp_hdrlen(skb);
> @@ -587,12 +592,22 @@ void ipoib_send(struct net_device *dev, struct sk_buff *skb,
>  	else
>  		priv->tx_wr.send_flags &= ~IB_SEND_IP_CSUM;
>  
> +	spin_lock_irqsave(&priv->lock, flags);
>  	if (++priv->tx_outstanding == ipoib_sendq_size) {
>  		ipoib_dbg(priv, "TX ring full, stopping kernel net queue\n");
>  		if (ib_req_notify_cq(priv->send_cq, IB_CQ_NEXT_COMP))
>  			ipoib_warn(priv, "request notify on send CQ failed\n");
>  		netif_stop_queue(dev);
>  	}
> +	spin_unlock_irqrestore(&priv->lock, flags);
> +	if (netif_queue_stopped(dev)) {
> +		rc = ib_req_notify_cq(priv->send_cq,
> +			IB_CQ_NEXT_COMP | IB_CQ_REPORT_MISSED_EVENTS);
> +		if (rc < 0)
> +			ipoib_warn(priv, "request notify on send CQ failed\n");
> +		else if (rc)
> +			ipoib_send_comp_handler(priv->send_cq, dev);
> +	}
>  
>  	skb_orphan(skb);
>  	skb_dst_drop(skb);
> @@ -602,11 +617,13 @@ void ipoib_send(struct net_device *dev, struct sk_buff *skb,
>  	if (unlikely(rc)) {
>  		ipoib_warn(priv, "post_send failed, error %d\n", rc);
>  		++dev->stats.tx_errors;
> +		spin_lock_irqsave(&priv->lock, flags);
>  		--priv->tx_outstanding;
> -		ipoib_dma_unmap_tx(priv, tx_req);
> -		dev_kfree_skb_any(skb);
>  		if (netif_queue_stopped(dev))
>  			netif_wake_queue(dev);
> +		spin_unlock_irqrestore(&priv->lock, flags);
> +		ipoib_dma_unmap_tx(priv, tx_req);
> +		dev_kfree_skb_any(skb);
>  	} else {
>  		dev->trans_start = jiffies;
>  
> @@ -825,6 +842,7 @@ int ipoib_ib_dev_stop(struct net_device *dev)
>  	unsigned long begin;
>  	struct ipoib_tx_buf *tx_req;
>  	int i;
> +	unsigned long flags;
>  
>  	if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
>  		napi_disable(&priv->napi);
> @@ -857,7 +875,9 @@ int ipoib_ib_dev_stop(struct net_device *dev)
>  				ipoib_dma_unmap_tx(priv, tx_req);
>  				dev_kfree_skb_any(tx_req->skb);
>  				++priv->tx_tail;
> +				spin_lock_irqsave(&priv->lock, flags);
>  				--priv->tx_outstanding;
> +				spin_unlock_irqrestore(&priv->lock, flags);
>  			}
>  
>  			for (i = 0; i < ipoib_recvq_size; ++i) {
> -- 
> 2.1.0
> 
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