netdev - RE: [PATCH] net: hns: Ensure that interface teardown cannot race with TX interrupt

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Message-ID: <164986f3ea2c4a21ab58f27b3c25190f@huawei.com>
Date:   Tue, 5 Nov 2019 09:16:18 +0000
From:   Salil Mehta <salil.mehta@...wei.com>
To:     Marc Zyngier <maz@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "lipeng (Y)" <lipeng321@...wei.com>,
        "Zhuangyuzeng (Yisen)" <yisen.zhuang@...wei.com>,
        "David S . Miller" <davem@...emloft.net>
Subject: RE: [PATCH] net: hns: Ensure that interface teardown cannot race with
 TX interrupt

Hi Marc,
Thanks for the catch & the patch. As such Looks good to me. For the sanity check,
I will try to reproduce the problem again and test it once with your patch.


Best Regards
Salil


> From: Marc Zyngier [mailto:maz@...nel.org]
> Sent: Monday, November 4, 2019 7:56 PM
> To: netdev@...r.kernel.org
> Cc: lipeng (Y) <lipeng321@...wei.com>; Zhuangyuzeng (Yisen)
> <yisen.zhuang@...wei.com>; Salil Mehta <salil.mehta@...wei.com>; David S .
> Miller <davem@...emloft.net>
> Subject: [PATCH] net: hns: Ensure that interface teardown cannot race with TX
> interrupt
> 
> On a lockdep-enabled kernel, bringing down a HNS interface results
> in a loud splat. It turns out that  the per-ring spinlock is taken
> both in the TX interrupt path, and when bringing down the interface.
> 
> Lockdep sums it up with:
> 
> [32099.424453]        CPU0
> [32099.426885]        ----
> [32099.429318]   lock(&(&ring->lock)->rlock);
> [32099.433402]   <Interrupt>
> [32099.436008]     lock(&(&ring->lock)->rlock);
> [32099.440264]
> [32099.440264]  *** DEADLOCK ***
> 
> To solve this, turn the NETIF_TX_{LOCK,UNLOCK} macros from standard
> spin_[un]lock to their irqsave/irqrestore version.
> 
> Fixes: f2aaed557ecff ("net: hns: Replace netif_tx_lock to ring spin lock")
> Cc: lipeng <lipeng321@...wei.com>
> Cc: Yisen Zhuang <yisen.zhuang@...wei.com>
> Cc: Salil Mehta <salil.mehta@...wei.com>
> Cc: David S. Miller <davem@...emloft.net>
> Signed-off-by: Marc Zyngier <maz@...nel.org>
> ---
>  drivers/net/ethernet/hisilicon/hns/hns_enet.c | 22 ++++++++++---------
>  1 file changed, 12 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> index a48396dd4ebb..9fbe4e1e6853 100644
> --- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> +++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c
> @@ -945,11 +945,11 @@ static int is_valid_clean_head(struct hnae_ring *ring,
> int h)
> 
>  /* netif_tx_lock will turn down the performance, set only when necessary */
>  #ifdef CONFIG_NET_POLL_CONTROLLER
> -#define NETIF_TX_LOCK(ring) spin_lock(&(ring)->lock)
> -#define NETIF_TX_UNLOCK(ring) spin_unlock(&(ring)->lock)
> +#define NETIF_TX_LOCK(ring, flags) spin_lock_irqsave(&(ring)->lock, flags)
> +#define NETIF_TX_UNLOCK(ring, flags) spin_unlock_irqrestore(&(ring)->lock,
> flags)
>  #else
> -#define NETIF_TX_LOCK(ring)
> -#define NETIF_TX_UNLOCK(ring)
> +#define NETIF_TX_LOCK(ring, flags)
> +#define NETIF_TX_UNLOCK(ring, flags)
>  #endif
> 
>  /* reclaim all desc in one budget
> @@ -962,16 +962,17 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data
> *ring_data,
>  	struct net_device *ndev = ring_data->napi.dev;
>  	struct netdev_queue *dev_queue;
>  	struct hns_nic_priv *priv = netdev_priv(ndev);
> +	unsigned long flags;
>  	int head;
>  	int bytes, pkts;
> 
> -	NETIF_TX_LOCK(ring);
> +	NETIF_TX_LOCK(ring, flags);
> 
>  	head = readl_relaxed(ring->io_base + RCB_REG_HEAD);
>  	rmb(); /* make sure head is ready before touch any data */
> 
>  	if (is_ring_empty(ring) || head == ring->next_to_clean) {
> -		NETIF_TX_UNLOCK(ring);
> +		NETIF_TX_UNLOCK(ring, flags);
>  		return 0; /* no data to poll */
>  	}
> 
> @@ -979,7 +980,7 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data
> *ring_data,
>  		netdev_err(ndev, "wrong head (%d, %d-%d)\n", head,
>  			   ring->next_to_use, ring->next_to_clean);
>  		ring->stats.io_err_cnt++;
> -		NETIF_TX_UNLOCK(ring);
> +		NETIF_TX_UNLOCK(ring, flags);
>  		return -EIO;
>  	}
> 
> @@ -994,7 +995,7 @@ static int hns_nic_tx_poll_one(struct hns_nic_ring_data
> *ring_data,
>  	ring->stats.tx_pkts += pkts;
>  	ring->stats.tx_bytes += bytes;
> 
> -	NETIF_TX_UNLOCK(ring);
> +	NETIF_TX_UNLOCK(ring, flags);
> 
>  	dev_queue = netdev_get_tx_queue(ndev, ring_data->queue_index);
>  	netdev_tx_completed_queue(dev_queue, pkts, bytes);
> @@ -1052,10 +1053,11 @@ static void hns_nic_tx_clr_all_bufs(struct
> hns_nic_ring_data *ring_data)
>  	struct hnae_ring *ring = ring_data->ring;
>  	struct net_device *ndev = ring_data->napi.dev;
>  	struct netdev_queue *dev_queue;
> +	unsigned long flags;
>  	int head;
>  	int bytes, pkts;
> 
> -	NETIF_TX_LOCK(ring);
> +	NETIF_TX_LOCK(ring, flags);
> 
>  	head = ring->next_to_use; /* ntu :soft setted ring position*/
>  	bytes = 0;
> @@ -1063,7 +1065,7 @@ static void hns_nic_tx_clr_all_bufs(struct
> hns_nic_ring_data *ring_data)
>  	while (head != ring->next_to_clean)
>  		hns_nic_reclaim_one_desc(ring, &bytes, &pkts);
> 
> -	NETIF_TX_UNLOCK(ring);
> +	NETIF_TX_UNLOCK(ring, flags);
> 
>  	dev_queue = netdev_get_tx_queue(ndev, ring_data->queue_index);
>  	netdev_tx_reset_queue(dev_queue);
> --
> 2.20.1