diff mbox series

[iwl-next,v6,1/6] igb: Always call igb_xdp_ring_update_tail() under Tx lock

Message ID 20240711-b4-igb_zero_copy-v6-1-4bfb68773b18@linutronix.de (mailing list archive)
State Awaiting Upstream
Delegated to: Netdev Maintainers
Headers show
Series igb: Add support for AF_XDP zero-copy | expand

Checks

Context Check Description
netdev/series_format warning Target tree name not specified in the subject
netdev/tree_selection success Guessed tree name to be net-next
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers success CCed 12 of 12 maintainers
netdev/build_clang success Errors and warnings before: 16 this patch: 16
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 16 this patch: 16
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 46 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 38 this patch: 38
netdev/source_inline success Was 0 now: 0

Commit Message

Kurt Kanzenbach Aug. 16, 2024, 9:24 a.m. UTC 
From: Sriram Yagnaraman <sriram.yagnaraman@est.tech>

Always call igb_xdp_ring_update_tail() under __netif_tx_lock(), add a
comment to indicate that. This is needed to share the same TX ring between
XDP, XSK and slow paths.

Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
[Kurt: Split patches]
Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Comments

Sebastian Andrzej Siewior Aug. 16, 2024, 9:38 a.m. UTC | #1 
On 2024-08-16 11:24:00 [+0200], Kurt Kanzenbach wrote:
> index 11be39f435f3..4d5e5691c9bd 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -2914,6 +2914,7 @@ static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>  	}
>  }
>  
> +/* This function assumes __netif_tx_lock is held by the caller. */
>  static void igb_xdp_ring_update_tail(struct igb_ring *ring)
>  {
>  	/* Force memory writes to complete before letting h/w know there
This
  lockdep_assert_held(txring_txq(ring)->_xmit_lock);
would be more powerful than the comment ;)

Sebastian
Kurt Kanzenbach Aug. 16, 2024, 9:56 a.m. UTC | #2 
On Fri Aug 16 2024, Sebastian Andrzej Siewior wrote:
> On 2024-08-16 11:24:00 [+0200], Kurt Kanzenbach wrote:
>> index 11be39f435f3..4d5e5691c9bd 100644
>> --- a/drivers/net/ethernet/intel/igb/igb_main.c
>> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
>> @@ -2914,6 +2914,7 @@ static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>>  	}
>>  }
>>  
>> +/* This function assumes __netif_tx_lock is held by the caller. */
>>  static void igb_xdp_ring_update_tail(struct igb_ring *ring)
>>  {
>>  	/* Force memory writes to complete before letting h/w know there
> This
>   lockdep_assert_held(txring_txq(ring)->_xmit_lock);
> would be more powerful than the comment ;)

Probably yes :-).

Thanks,
Kurt
Fijalkowski, Maciej Aug. 19, 2024, 1:07 p.m. UTC | #3 
On Fri, Aug 16, 2024 at 11:24:00AM +0200, Kurt Kanzenbach wrote:
> From: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> 
> Always call igb_xdp_ring_update_tail() under __netif_tx_lock(), add a
> comment to indicate that. This is needed to share the same TX ring between
> XDP, XSK and slow paths.

Sorry for being a-hole here but I think this should go to -net as a fix...
I should have brought it up earlier, current igb XDP support is racy on
tail updates which you're fixing here.

Do you agree...or not?:)

> 
> Signed-off-by: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
> [Kurt: Split patches]
> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de>
> ---
>  drivers/net/ethernet/intel/igb/igb_main.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 11be39f435f3..4d5e5691c9bd 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -2914,6 +2914,7 @@ static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
>  	}
>  }
>  
> +/* This function assumes __netif_tx_lock is held by the caller. */
>  static void igb_xdp_ring_update_tail(struct igb_ring *ring)
>  {
>  	/* Force memory writes to complete before letting h/w know there
> @@ -3000,11 +3001,11 @@ static int igb_xdp_xmit(struct net_device *dev, int n,
>  		nxmit++;
>  	}
>  
> -	__netif_tx_unlock(nq);
> -
>  	if (unlikely(flags & XDP_XMIT_FLUSH))
>  		igb_xdp_ring_update_tail(tx_ring);
>  
> +	__netif_tx_unlock(nq);
> +
>  	return nxmit;
>  }
>  
> @@ -8853,12 +8854,14 @@ static void igb_put_rx_buffer(struct igb_ring *rx_ring,
>  
>  static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  {
> +	unsigned int total_bytes = 0, total_packets = 0;
>  	struct igb_adapter *adapter = q_vector->adapter;
>  	struct igb_ring *rx_ring = q_vector->rx.ring;
> -	struct sk_buff *skb = rx_ring->skb;
> -	unsigned int total_bytes = 0, total_packets = 0;
>  	u16 cleaned_count = igb_desc_unused(rx_ring);
> +	struct sk_buff *skb = rx_ring->skb;
> +	int cpu = smp_processor_id();
>  	unsigned int xdp_xmit = 0;
> +	struct netdev_queue *nq;
>  	struct xdp_buff xdp;
>  	u32 frame_sz = 0;
>  	int rx_buf_pgcnt;
> @@ -8986,7 +8989,10 @@ static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
>  	if (xdp_xmit & IGB_XDP_TX) {
>  		struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);
>  
> +		nq = txring_txq(tx_ring);
> +		__netif_tx_lock(nq, cpu);
>  		igb_xdp_ring_update_tail(tx_ring);
> +		__netif_tx_unlock(nq);
>  	}
>  
>  	u64_stats_update_begin(&rx_ring->rx_syncp);
> 
> -- 
> 2.39.2
>
Kurt Kanzenbach Aug. 19, 2024, 2:21 p.m. UTC | #4 
On Mon Aug 19 2024, Maciej Fijalkowski wrote:
> On Fri, Aug 16, 2024 at 11:24:00AM +0200, Kurt Kanzenbach wrote:
>> From: Sriram Yagnaraman <sriram.yagnaraman@est.tech>
>> 
>> Always call igb_xdp_ring_update_tail() under __netif_tx_lock(), add a
>> comment to indicate that. This is needed to share the same TX ring between
>> XDP, XSK and slow paths.
>
> Sorry for being a-hole here but I think this should go to -net as a fix...
> I should have brought it up earlier, current igb XDP support is racy on
> tail updates which you're fixing here.
>
> Do you agree...or not?:)

Yeah, makes sense. I'll add a Fixes tag and send it to iwl-net.

Thanks,
Kurt
diff mbox series

Patch

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 11be39f435f3..4d5e5691c9bd 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -2914,6 +2914,7 @@  static int igb_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }
 
+/* This function assumes __netif_tx_lock is held by the caller. */
 static void igb_xdp_ring_update_tail(struct igb_ring *ring)
 {
 	/* Force memory writes to complete before letting h/w know there
@@ -3000,11 +3001,11 @@  static int igb_xdp_xmit(struct net_device *dev, int n,
 		nxmit++;
 	}
 
-	__netif_tx_unlock(nq);
-
 	if (unlikely(flags & XDP_XMIT_FLUSH))
 		igb_xdp_ring_update_tail(tx_ring);
 
+	__netif_tx_unlock(nq);
+
 	return nxmit;
 }
 
@@ -8853,12 +8854,14 @@  static void igb_put_rx_buffer(struct igb_ring *rx_ring,
 
 static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 {
+	unsigned int total_bytes = 0, total_packets = 0;
 	struct igb_adapter *adapter = q_vector->adapter;
 	struct igb_ring *rx_ring = q_vector->rx.ring;
-	struct sk_buff *skb = rx_ring->skb;
-	unsigned int total_bytes = 0, total_packets = 0;
 	u16 cleaned_count = igb_desc_unused(rx_ring);
+	struct sk_buff *skb = rx_ring->skb;
+	int cpu = smp_processor_id();
 	unsigned int xdp_xmit = 0;
+	struct netdev_queue *nq;
 	struct xdp_buff xdp;
 	u32 frame_sz = 0;
 	int rx_buf_pgcnt;
@@ -8986,7 +8989,10 @@  static int igb_clean_rx_irq(struct igb_q_vector *q_vector, const int budget)
 	if (xdp_xmit & IGB_XDP_TX) {
 		struct igb_ring *tx_ring = igb_xdp_tx_queue_mapping(adapter);
 
+		nq = txring_txq(tx_ring);
+		__netif_tx_lock(nq, cpu);
 		igb_xdp_ring_update_tail(tx_ring);
+		__netif_tx_unlock(nq);
 	}
 
 	u64_stats_update_begin(&rx_ring->rx_syncp);