Re: [PATCH V7 net] net: mana: Fix MANA VF unload when hardware is

From: Jesse Brandeburg <jesse.brandeburg@intel.com>
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>
Subject: Re: [PATCH V7 net] net: mana: Fix MANA VF unload when hardware is
Date: Tue, 1 Aug 2023 11:04:26 -0700	[thread overview]
Message-ID: <8ccbfab0-e24f-b758-cd11-27b6d8ab1d48@intel.com> (raw)
In-Reply-To: <1690892953-25201-1-git-send-email-schakrabarti@linux.microsoft.com>

On 8/1/2023 5:29 AM, 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,

tx timeout in stack defaults to 5 seconds, do you not have that on? What
happens when you start getting resets while unloading?

> which is a somewhat arbitrary value that is more than long enough for
> functional hardware to complete any sends.

I'd say 2 or 5 seconds is probably plenty of time to hang up a driver
unload.

> 
> 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>

keep s-o-b and other trailers together please, no spaces, it messes up
git and doesn't conform to kernel standards.

> ---
> V6 -> V7:
> * Optimized the while loop for freeing skb.
> 
> 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 | 37 +++++++++++++++++--
>  1 file changed, 33 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..3c5552a176d0 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 +2367,40 @@ 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 (skb = skb_dequeue(&txq->pending_skbs)) {
> +			mana_unmap_skb(skb, apc);
> +			dev_consume_skb_any(skb);

dev_kfree_skb_any() would be more correct here since this is an error
path and the transmit is presumed dropped, isn't it?

> +		}
> +		atomic_set(&txq->pending_sends, 0);
> +	}
>  	/* 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.
>  	 */