linux-kernel - Re: [PATCH V5 net] net: mana: Fix MANA VF unload when hardware is unresponsive

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Message-ID: <062d9a4a0ec07e0c498fb7c6b8aab9d27177b21a.camel@redhat.com>
Date:   Thu, 06 Jul 2023 10:18:51 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>,
        kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org,
        decui@...rosoft.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, longli@...rosoft.com, sharmaajay@...rosoft.com,
        leon@...nel.org, cai.huoqing@...ux.dev,
        ssengar@...ux.microsoft.com, vkuznets@...hat.com,
        tglx@...utronix.de, linux-hyperv@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rdma@...r.kernel.org
Cc:     stable@...r.kernel.org, schakrabarti@...rosoft.com
Subject: Re: [PATCH V5 net] net: mana: Fix MANA VF unload when hardware is
 unresponsive

On Wed, 2023-07-05 at 01:16 -0700, Souradeep Chakrabarti wrote:
> 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.
> 
> Fixes: ca9c54d2d6a5 ("net: mana: Add a driver for Microsoft Azure Network Adapter (MANA)")
> ---
> V4 -> V5:
> * Added fixes tag
> * Changed the usleep_range from static to incremental value.
> * Initialized timeout in the begining.
> ---
> Signed-off-by: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>

the changelog should come after the SoB tag, and there should be no '--
- ' separator before the SoB.

Please double-check your patch with the checkpatch script before the
next submission, it should catch trivial issues as the above one.

> ---
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 30 ++++++++++++++++---
>  1 file changed, 26 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..56b7074db1a2 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -2345,9 +2345,13 @@ 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;
> +	struct mana_cq *cq;
>  	int i, err;
> +	u32 tsleep;
>  
>  	if (apc->port_is_up)
>  		return -EINVAL;
> @@ -2363,15 +2367,33 @@ 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 << 1);
> +			tsleep <<= 1;
> +		}
>  	}
>  
> +	for (i = 0; i < apc->num_queues; i++) {
> +		txq = &apc->tx_qp[i].txq;
> +		cq = &apc->tx_qp[i].tx_cq;

The above variable is unused, and causes a build warning. Please remove
the assignment and the variable declaration.

Thanks,

Paolo