linux-kernel - Re: [PATCH net-next v3 3/3] net: hinic: fix bug that u64_stats

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Date:   Tue, 5 Jul 2022 10:53:51 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Qiao Ma <mqaio@...ux.alibaba.com>
Cc:     David Miller <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>, gustavoars@...nel.org,
        cai.huoqing@...ux.dev, Aviad Krawczyk <aviad.krawczyk@...wei.com>,
        zhaochen6@...wei.com, netdev <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next v3 3/3] net: hinic: fix bug that u64_stats_sync
 is not initialized

On Tue, Jul 5, 2022 at 8:26 AM Qiao Ma <mqaio@...ux.alibaba.com> wrote:
>
> In get_drv_queue_stats(), the local variable {txq|rxq}_stats
> should be initialized first before calling into
> hinic_{rxq|txq}_get_stats(), this patch fixes it.
>
> Fixes: edd384f682cc ("net-next/hinic: Add ethtool and stats")
> Signed-off-by: Qiao Ma <mqaio@...ux.alibaba.com>
> ---
>  drivers/net/ethernet/huawei/hinic/hinic_ethtool.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
> index 93192f58ac88..75e9711bd2ba 100644
> --- a/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
> +++ b/drivers/net/ethernet/huawei/hinic/hinic_ethtool.c
> @@ -1371,6 +1371,9 @@ static void get_drv_queue_stats(struct hinic_dev *nic_dev, u64 *data)
>         u16 i = 0, j = 0, qid = 0;
>         char *p;
>
> +       u64_stats_init(&txq_stats.syncp);
> +       u64_stats_init(&rxq_stats.syncp);
> +

This is wrong really.

txq_stats and rxq_stats are local variables in get_drv_queue_stats()

It makes little sense to use u64_stats infra on them, because they are
not visible to other cpus/threads in the host.

Please remove this confusion, instead of consolidating it.

diff --git a/drivers/net/ethernet/huawei/hinic/hinic_main.c
b/drivers/net/ethernet/huawei/hinic/hinic_main.c
index 56a89793f47d4209b9e0dc3a122801d476e61381..edaac5a33458d51a3fb3e75c5fbe5bec8385f688
100644
--- a/drivers/net/ethernet/huawei/hinic/hinic_main.c
+++ b/drivers/net/ethernet/huawei/hinic/hinic_main.c
@@ -85,8 +85,6 @@ static void update_rx_stats(struct hinic_dev
*nic_dev, struct hinic_rxq *rxq)
        struct hinic_rxq_stats *nic_rx_stats = &nic_dev->rx_stats;
        struct hinic_rxq_stats rx_stats;

-       u64_stats_init(&rx_stats.syncp);
-
        hinic_rxq_get_stats(rxq, &rx_stats);

        u64_stats_update_begin(&nic_rx_stats->syncp);
@@ -105,8 +103,6 @@ static void update_tx_stats(struct hinic_dev
*nic_dev, struct hinic_txq *txq)
        struct hinic_txq_stats *nic_tx_stats = &nic_dev->tx_stats;
        struct hinic_txq_stats tx_stats;

-       u64_stats_init(&tx_stats.syncp);
-
        hinic_txq_get_stats(txq, &tx_stats);

        u64_stats_update_begin(&nic_tx_stats->syncp);
diff --git a/drivers/net/ethernet/huawei/hinic/hinic_rx.c
b/drivers/net/ethernet/huawei/hinic/hinic_rx.c
index 24b7b819dbfbad1d64116ef54058ee4887d7a056..4edf4c52787051aebc512094741bda30de27e2f0
100644
--- a/drivers/net/ethernet/huawei/hinic/hinic_rx.c
+++ b/drivers/net/ethernet/huawei/hinic/hinic_rx.c
@@ -66,14 +66,13 @@ void hinic_rxq_clean_stats(struct hinic_rxq *rxq)
 /**
  * hinic_rxq_get_stats - get statistics of Rx Queue
  * @rxq: Logical Rx Queue
- * @stats: return updated stats here
+ * @stats: return updated stats here (private to caller)
  **/
 void hinic_rxq_get_stats(struct hinic_rxq *rxq, struct hinic_rxq_stats *stats)
 {
-       struct hinic_rxq_stats *rxq_stats = &rxq->rxq_stats;
+       const struct hinic_rxq_stats *rxq_stats = &rxq->rxq_stats;
        unsigned int start;

-       u64_stats_update_begin(&stats->syncp);
        do {
                start = u64_stats_fetch_begin(&rxq_stats->syncp);
                stats->pkts = rxq_stats->pkts;
@@ -83,7 +82,6 @@ void hinic_rxq_get_stats(struct hinic_rxq *rxq,
struct hinic_rxq_stats *stats)
                stats->csum_errors = rxq_stats->csum_errors;
                stats->other_errors = rxq_stats->other_errors;
        } while (u64_stats_fetch_retry(&rxq_stats->syncp, start));
-       u64_stats_update_end(&stats->syncp);
 }

 /**
diff --git a/drivers/net/ethernet/huawei/hinic/hinic_tx.c
b/drivers/net/ethernet/huawei/hinic/hinic_tx.c
index 87408e7bb8097de6fced7f0f2d170179b3fe93a9..2d97add1107f08f088b68a823767a92cbc6bbbdf
100644
--- a/drivers/net/ethernet/huawei/hinic/hinic_tx.c
+++ b/drivers/net/ethernet/huawei/hinic/hinic_tx.c
@@ -91,14 +91,13 @@ void hinic_txq_clean_stats(struct hinic_txq *txq)
 /**
  * hinic_txq_get_stats - get statistics of Tx Queue
  * @txq: Logical Tx Queue
- * @stats: return updated stats here
+ * @stats: return updated stats here (private to caller)
  **/
 void hinic_txq_get_stats(struct hinic_txq *txq, struct hinic_txq_stats *stats)
 {
-       struct hinic_txq_stats *txq_stats = &txq->txq_stats;
+       const struct hinic_txq_stats *txq_stats = &txq->txq_stats;
        unsigned int start;

-       u64_stats_update_begin(&stats->syncp);
        do {
                start = u64_stats_fetch_begin(&txq_stats->syncp);
                stats->pkts    = txq_stats->pkts;
@@ -108,7 +107,6 @@ void hinic_txq_get_stats(struct hinic_txq *txq,
struct hinic_txq_stats *stats)
                stats->tx_dropped = txq_stats->tx_dropped;
                stats->big_frags_pkts = txq_stats->big_frags_pkts;
        } while (u64_stats_fetch_retry(&txq_stats->syncp, start));
-       u64_stats_update_end(&stats->syncp);
 }

 /**