Re: [PATCH] IPoIB: serialize changing on tx_outstanding

[Wengang Wang <wen.gang.wang-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Hi Leon,

thanks for review.

在 2015年10月08日 12:33, Leon Romanovsky 写道:
> 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?

Yes, I intended to do that.   This make the accessing on tx_outstanding 
and the reopening of the send queue in the same atomic session which is 
the expected behavior.
Otherwise,  we may have the following problem:
#time order

thread1(on cpu1) thread2(on cpu2)
lock
modify/check tx_outstanding
unlock


lock
modify/check tx_outstanding
unlock

reopen queue


                        stop queue


So that we actually want reopen the send queue, but the result is we 
stopped it.

thanks,
wengang

>>   		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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