netdev - RE: [Intel-wired-lan] [PATCH net] idpf: Fix data race in idpf_net

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Message-ID: <IA3PR11MB89869E1AEBB3C8908546ACBFE597A@IA3PR11MB8986.namprd11.prod.outlook.com>
Date: Thu, 22 Jan 2026 11:26:40 +0000
From: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
To: David Yang <mmyangfl@...il.com>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Pavan Kumar
 Linga" <pavan.kumar.linga@...el.com>, "Burra, Phani R"
	<phani.r.burra@...el.com>, Willem de Bruijn <willemb@...gle.com>, Alan Brady
	<alan.brady@...el.com>, "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
	"Hay, Joshua A" <joshua.a.hay@...el.com>, "intel-wired-lan@...ts.osuosl.org"
	<intel-wired-lan@...ts.osuosl.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>
Subject: RE: [Intel-wired-lan] [PATCH net] idpf: Fix data race in idpf_net_dim



> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf
> Of David Yang
> Sent: Monday, January 19, 2026 5:27 PM
> To: netdev@...r.kernel.org
> Cc: David Yang <mmyangfl@...il.com>; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@...el.com>; Andrew Lunn <andrew+netdev@...n.ch>;
> David S. Miller <davem@...emloft.net>; Eric Dumazet
> <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; Pavan Kumar Linga <pavan.kumar.linga@...el.com>;
> Burra, Phani R <phani.r.burra@...el.com>; Willem de Bruijn
> <willemb@...gle.com>; Alan Brady <alan.brady@...el.com>; Samudrala,
> Sridhar <sridhar.samudrala@...el.com>; Hay, Joshua A
> <joshua.a.hay@...el.com>; intel-wired-lan@...ts.osuosl.org; linux-
> kernel@...r.kernel.org
> Subject: [Intel-wired-lan] [PATCH net] idpf: Fix data race in
> idpf_net_dim
> 
> In idpf_net_dim(), some statistics protected by u64_stats_sync, are
> read and accumulated in ignorance of possible u64_stats_fetch_retry()
> events.
> The correct way to copy statistics is already illustrated by
> idpf_add_queue_stats(). Fix this by reading them into temporary
> variables first.
> 
> Fixes: c2d548cad150 ("idpf: add TX splitq napi poll support")
> Fixes: 3a8845af66ed ("idpf: add RX splitq napi poll support")
> Signed-off-by: David Yang <mmyangfl@...il.com>
> ---
>  drivers/net/ethernet/intel/idpf/idpf_txrx.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> index 97a5fe766b6b..66ba645e8b90 100644
> --- a/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> +++ b/drivers/net/ethernet/intel/idpf/idpf_txrx.c
> @@ -3956,7 +3956,7 @@ static void idpf_update_dim_sample(struct
> idpf_q_vector *q_vector,  static void idpf_net_dim(struct
> idpf_q_vector *q_vector)  {
>  	struct dim_sample dim_sample = { };
> -	u64 packets, bytes;
> +	u64 packets, bytes, pkts, bts;
>  	u32 i;
> 
>  	if (!IDPF_ITR_IS_DYNAMIC(q_vector->tx_intr_mode))
> @@ -3968,9 +3968,12 @@ static void idpf_net_dim(struct idpf_q_vector
> *q_vector)
> 
>  		do {
>  			start = u64_stats_fetch_begin(&txq->stats_sync);
> -			packets += u64_stats_read(&txq->q_stats.packets);
> -			bytes += u64_stats_read(&txq->q_stats.bytes);
> +			pkts = u64_stats_read(&txq->q_stats.packets);
> +			bts = u64_stats_read(&txq->q_stats.bytes);
>  		} while (u64_stats_fetch_retry(&txq->stats_sync,
> start));
> +
> +		packets += pkts;
> +		bytes += bts;
>  	}
> 
>  	idpf_update_dim_sample(q_vector, &dim_sample, &q_vector-
> >tx_dim, @@ -3987,9 +3990,12 @@ static void idpf_net_dim(struct
> idpf_q_vector *q_vector)
> 
>  		do {
>  			start = u64_stats_fetch_begin(&rxq->stats_sync);
> -			packets += u64_stats_read(&rxq->q_stats.packets);
> -			bytes += u64_stats_read(&rxq->q_stats.bytes);
> +			pkts = u64_stats_read(&rxq->q_stats.packets);
> +			bts = u64_stats_read(&rxq->q_stats.bytes);
>  		} while (u64_stats_fetch_retry(&rxq->stats_sync,
> start));
> +
> +		packets += pkts;
> +		bytes += bts;
>  	}
> 
>  	idpf_update_dim_sample(q_vector, &dim_sample, &q_vector-
> >rx_dim,
> --
> 2.51.0

Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@...el.com>