> -----Original Message-----
> From: Intel-wired-lan <[email protected]> On Behalf
> Of Alex Dvoretsky
> Sent: Friday, March 6, 2026 10:13 PM
> To: [email protected]
> Cc: [email protected]; Nguyen, Anthony L
> <[email protected]>; Kitszel, Przemyslaw
> <[email protected]>; [email protected];
> [email protected]; Fijalkowski, Maciej
> <[email protected]>; Alex Dvoretsky <[email protected]>
> Subject: [Intel-wired-lan] [PATCH net 3/3] igb: add XDP transition
> guards in igb_xdp_setup()
>
> igb_xdp_setup() calls igb_close() + igb_open() when transitioning
> between XDP and non-XDP mode on a running device. This has two issues:
>
> 1. ndo_xsk_wakeup() runs under rcu_read_lock() and may still access
> the rings while igb_xdp_setup() removes the XDP program. Without
> waiting for an RCU grace period, igb_close() can tear down the
> rings while ndo_xsk_wakeup() is still executing. Add
> synchronize_rcu() before igb_close() when removing an XDP program
> to ensure all in-flight RCU readers complete first.
>
> 2. The igb_close()/igb_open() window leaves trans_start stale from
> before the close: the TX watchdog can fire a spurious timeout and
> queue a reset_task that races with igb_open(). Add
> netif_trans_update() after igb_open() to refresh the timestamp, and
> cancel_work() to cancel any reset_task that may have been queued
> while the device was down.
>
> Note: cancel_work_sync() cannot be used here because igb_reset_task()
> takes rtnl_lock, which is already held by the ndo_bpf caller. Plain
> cancel_work() is sufficient: if reset_task is already running, it
> blocks on rtnl_lock and will check __IGB_DOWN when it acquires it.
>
> Fixes: 9cbc948b5a20 ("igb: add XDP support")
> Cc: [email protected]
> Signed-off-by: Alex Dvoretsky <[email protected]>
> ---
> drivers/net/ethernet/intel/igb/igb_main.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index ddb7ce9e97bf..9ba944bf67b4 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -2913,6 +2913,9 @@ static int igb_xdp_setup(struct net_device *dev,
> struct netdev_bpf *bpf)
>
> /* device is up and bpf is added/removed, must setup the RX
> queues */
> if (need_reset && running) {
> + if (!prog)
> + /* Wait for RCU readers (e.g. ndo_xsk_wakeup). */
> + synchronize_rcu();
> igb_close(dev);
> } else {
> for (i = 0; i < adapter->num_rx_queues; i++) @@ -2936,6
> +2939,14 @@ static int igb_xdp_setup(struct net_device *dev, struct
> netdev_bpf *bpf)
> if (running)
> igb_open(dev);
>
> + /* Refresh watchdog timestamp after reopen and cancel any
> + * reset task queued while the device was down.
> + */
> + if (need_reset && running) {
> + netif_trans_update(dev);
> + cancel_work(&adapter->reset_task);
> + }
> +
> return 0;
> }
>
> --
> 2.51.0
Reviewed-by: Aleksandr Loktionov <[email protected]>
