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Date:   Thu, 27 Jul 2023 11:10:37 +0800
MIME-Version: 1.0
Subject: Re: [PATCH V6 net] net: mana: Fix MANA VF unload when hardware is
To:     Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>,
        kys@microsoft.com, haiyangz@microsoft.com, wei.liu@kernel.org,
        decui@microsoft.com, davem@davemloft.net, edumazet@google.com,
        kuba@kernel.org, pabeni@redhat.com, longli@microsoft.com,
        sharmaajay@microsoft.com, leon@kernel.org, cai.huoqing@linux.dev,
        ssengar@linux.microsoft.com, vkuznets@redhat.com,
        tglx@linutronix.de, linux-hyperv@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rdma@vger.kernel.org
Cc:     schakrabarti@microsoft.com, stable@vger.kernel.org
References: <1690377336-1353-1-git-send-email-schakrabarti@linux.microsoft.com>
From:   Zhu Yanjun <yanjun.zhu@linux.dev>
In-Reply-To: <1690377336-1353-1-git-send-email-schakrabarti@linux.microsoft.com>
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在 2023/7/26 21:15, Souradeep Chakrabarti 写道:
> When unloading the MANA driver, mana_dealloc_queues() waits for the MANA
> hardware to complete any inflight packets and set the pending send count
> to zero. But if the hardware has failed, mana_dealloc_queues()
> could wait forever.
> 
> Fix this by adding a timeout to the wait. Set the timeout to 120 seconds,
> which is a somewhat arbitrary value that is more than long enough for
> functional hardware to complete any sends.
> 
> Cc: stable@vger.kernel.org
> Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
> 
> Signed-off-by: Souradeep Chakrabarti <schakrabarti@linux.microsoft.com>
> ---
> V5 -> V6:
> * Added pcie_flr to reset the pci after timeout.
> * Fixed the position of changelog.
> * Removed unused variable like cq.
> 
> V4 -> V5:
> * Added fixes tag
> * Changed the usleep_range from static to incremental value.
> * Initialized timeout in the begining.
> 
> V3 -> V4:
> * Removed the unnecessary braces from mana_dealloc_queues().
> 
> V2 -> V3:
> * Removed the unnecessary braces from mana_dealloc_queues().
> 
> V1 -> V2:
> * Added net branch
> * Removed the typecasting to (struct mana_context*) of void pointer
> * Repositioned timeout variable in mana_dealloc_queues()
> * Repositioned vf_unload_timeout in mana_context struct, to utilise the
>   6 bytes hole
> ---
>   drivers/net/ethernet/microsoft/mana/mana_en.c | 38 +++++++++++++++++--
>   1 file changed, 34 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index a499e460594b..ea039e2d4c4b 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -8,6 +8,7 @@
>   #include <linux/ethtool.h>
>   #include <linux/filter.h>
>   #include <linux/mm.h>
> +#include <linux/pci.h>
>   
>   #include <net/checksum.h>
>   #include <net/ip6_checksum.h>
> @@ -2345,9 +2346,12 @@ int mana_attach(struct net_device *ndev)
>   static int mana_dealloc_queues(struct net_device *ndev)
>   {
>   	struct mana_port_context *apc = netdev_priv(ndev);
> +	unsigned long timeout = jiffies + 120 * HZ;
>   	struct gdma_dev *gd = apc->ac->gdma_dev;
>   	struct mana_txq *txq;
> +	struct sk_buff *skb;
>   	int i, err;
> +	u32 tsleep;
>   
>   	if (apc->port_is_up)
>   		return -EINVAL;
> @@ -2363,15 +2367,41 @@ static int mana_dealloc_queues(struct net_device *ndev)
>   	 * to false, but it doesn't matter since mana_start_xmit() drops any
>   	 * new packets due to apc->port_is_up being false.
>   	 *
> -	 * Drain all the in-flight TX packets
> +	 * Drain all the in-flight TX packets.
> +	 * A timeout of 120 seconds for all the queues is used.
> +	 * This will break the while loop when h/w is not responding.
> +	 * This value of 120 has been decided here considering max
> +	 * number of queues.
>   	 */
> +
>   	for (i = 0; i < apc->num_queues; i++) {
>   		txq = &apc->tx_qp[i].txq;
> -
> -		while (atomic_read(&txq->pending_sends) > 0)
> -			usleep_range(1000, 2000);
> +		tsleep = 1000;
> +		while (atomic_read(&txq->pending_sends) > 0 &&
> +		       time_before(jiffies, timeout)) {
> +			usleep_range(tsleep, tsleep + 1000);
> +			tsleep <<= 1;
> +		}
> +		if (atomic_read(&txq->pending_sends)) {
> +			err  = pcie_flr(to_pci_dev(gd->gdma_context->dev));
> +			if (err) {
> +				netdev_err(ndev, "flr failed %d with %d pkts pending in txq %u\n",
> +					   err, atomic_read(&txq->pending_sends),
> +					   txq->gdma_txq_id);
> +			}
> +			break;
> +		}
>   	}
>   
> +	for (i = 0; i < apc->num_queues; i++) {
> +		txq = &apc->tx_qp[i].txq;
> +		while (atomic_read(&txq->pending_sends)) {
> +			skb = skb_dequeue(&txq->pending_skbs);
> +			mana_unmap_skb(skb, apc);
> +			dev_consume_skb_any(skb);
> +			atomic_sub(1, &txq->pending_sends);
> +		}
If I get this commit correctly, txq->pending_sends should be equal to 
the length of txq->pending_skbs?

If yes, can we only handle the pending_skbs?

the above snippet can be changed to as below? So the performance is better?
"
		while ((skb = skb_dequeue(&txq->pending_skbs))) {
			mana_unmap_skb(skb, apc);
			dev_consume_skb_any(skb);
		}
		atomic_set(&txq->pending_sends, 0);
"

Zhu Yanjun

> +	}
>   	/* We're 100% sure the queues can no longer be woken up, because
>   	 * we're sure now mana_poll_tx_cq() can't be running.
>   	 */