linux-kernel - RE: [PATCH V4 net] net: mana: Fix MANA VF unload when host is unresponsive

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Message-ID: <PH7PR21MB31166AAAE7225559D751F722CA29A@PH7PR21MB3116.namprd21.prod.outlook.com>
Date:   Mon, 3 Jul 2023 15:51:28 +0000
From:   Haiyang Zhang <haiyangz@...rosoft.com>
To:     souradeep chakrabarti <schakrabarti@...ux.microsoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        Long Li <longli@...rosoft.com>,
        Ajay Sharma <sharmaajay@...rosoft.com>,
        "leon@...nel.org" <leon@...nel.org>,
        "cai.huoqing@...ux.dev" <cai.huoqing@...ux.dev>,
        "ssengar@...ux.microsoft.com" <ssengar@...ux.microsoft.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
CC:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Souradeep Chakrabarti <schakrabarti@...rosoft.com>
Subject: RE: [PATCH V4 net] net: mana: Fix MANA VF unload when host is
 unresponsive



> -----Original Message-----
> From: souradeep chakrabarti <schakrabarti@...ux.microsoft.com>
> Sent: Monday, July 3, 2023 4:50 AM
> To: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; wei.liu@...nel.org; Dexuan Cui
> <decui@...rosoft.com>; davem@...emloft.net; edumazet@...gle.com;
> kuba@...nel.org; pabeni@...hat.com; Long Li <longli@...rosoft.com>; Ajay
> Sharma <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; Souradeep Chakrabarti
> <schakrabarti@...rosoft.com>; Souradeep Chakrabarti
> <schakrabarti@...ux.microsoft.com>
> Subject: [PATCH V4 net] net: mana: Fix MANA VF unload when host is
> unresponsive
> 
> From: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
> 
> 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.
> 
> Signed-off-by: Souradeep Chakrabarti <schakrabarti@...ux.microsoft.com>
> ---
> V3 -> V4:
> * Fixed the commit message to describe the context.
> * Removed the vf_unload_timeout, as it is not required.
> ---
>  drivers/net/ethernet/microsoft/mana/mana_en.c | 26 ++++++++++++++++---
>  1 file changed, 23 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/ethernet/microsoft/mana/mana_en.c
> b/drivers/net/ethernet/microsoft/mana/mana_en.c
> index a499e460594b..d26f1da70411 100644
> --- a/drivers/net/ethernet/microsoft/mana/mana_en.c
> +++ b/drivers/net/ethernet/microsoft/mana/mana_en.c
> @@ -2346,7 +2346,10 @@ static int mana_dealloc_queues(struct net_device
> *ndev)
>  {
>  	struct mana_port_context *apc = netdev_priv(ndev);
>  	struct gdma_dev *gd = apc->ac->gdma_dev;
> +	unsigned long timeout;
>  	struct mana_txq *txq;
> +	struct sk_buff *skb;
> +	struct mana_cq *cq;
>  	int i, err;
> 
>  	if (apc->port_is_up)
> @@ -2363,15 +2366,32 @@ 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.
>  	 */
> +
> +	timeout = jiffies + 120 * HZ;
>  	for (i = 0; i < apc->num_queues; i++) {
>  		txq = &apc->tx_qp[i].txq;
> -
> -		while (atomic_read(&txq->pending_sends) > 0)
> +		while (atomic_read(&txq->pending_sends) > 0 &&
> +		       time_before(jiffies, timeout)) {
>  			usleep_range(1000, 2000);
> +		}
>  	}
> 
> +	for (i = 0; i < apc->num_queues; i++) {
> +		txq = &apc->tx_qp[i].txq;
> +		cq = &apc->tx_qp[i].tx_cq;
> +		while (atomic_read(&txq->pending_sends)) {
> +			skb = skb_dequeue(&txq->pending_skbs);
> +			mana_unmap_skb(skb, apc);
> +			napi_consume_skb(skb, cq->budget);

This is not in NAPI context, so it should be dev_consume_skb_any()

Thanks,
- Haiyang