On 06.11.24 13:01, Greg Kroah-Hartman wrote:
> 6.11-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Wander Lairson Costa <wander@xxxxxxxxxx>
>
> [ Upstream commit 338c4d3902feb5be49bfda530a72c7ab860e2c9f ]
>
> During testing of SR-IOV, Red Hat QE encountered an issue where the
> ip link up command intermittently fails for the igbvf interfaces when
> using the PREEMPT_RT variant. Investigation revealed that
> e1000_write_posted_mbx returns an error due to the lack of an ACK
> from e1000_poll_for_ack.
>
> The underlying issue arises from the fact that IRQs are threaded by
> default under PREEMPT_RT. While the exact hardware details are not
> available, it appears that the IRQ handled by igb_msix_other must
> be processed before e1000_poll_for_ack times out. However,
> e1000_write_posted_mbx is called with preemption disabled, leading
> to a scenario where the IRQ is serviced only after the failure of
> e1000_write_posted_mbx.
>
> To resolve this, we set IRQF_NO_THREAD for the affected interrupt,
> ensuring that the kernel handles it immediately, thereby preventing
> the aforementioned error.
>
> Reproducer:
>
> #!/bin/bash
>
> # echo 2 > /sys/class/net/ens14f0/device/sriov_numvfs
> ipaddr_vlan=3
> nic_test=ens14f0
> vf=${nic_test}v0
>
> while true; do
> ip link set ${nic_test} mtu 1500
> ip link set ${vf} mtu 1500
> ip link set $vf up
> ip link set ${nic_test} vf 0 vlan ${ipaddr_vlan}
> ip addr add 172.30.${ipaddr_vlan}.1/24 dev ${vf}
> ip addr add 2021:db8:${ipaddr_vlan}::1/64 dev ${vf}
> if ! ip link show $vf | grep 'state UP'; then
> echo 'Error found'
> break
> fi
> ip link set $vf down
> done
>
> Signed-off-by: Wander Lairson Costa <wander@xxxxxxxxxx>
> Fixes: 9d5c824399de ("igb: PCI-Express 82575 Gigabit Ethernet driver")
> Reported-by: Yuying Ma <yuma@xxxxxxxxxx>
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@xxxxxxxxx>
> Tested-by: Rafal Romanowski <rafal.romanowski@xxxxxxxxx>
> Signed-off-by: Jacob Keller <jacob.e.keller@xxxxxxxxx>
> Reviewed-by: Simon Horman <horms@xxxxxxxxxx>
> Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
> ---
> drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index f1d0881687233..b83df5f94b1f5 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -907,7 +907,7 @@ static int igb_request_msix(struct igb_adapter *adapter)
> int i, err = 0, vector = 0, free_vector = 0;
>
> err = request_irq(adapter->msix_entries[vector].vector,
> - igb_msix_other, 0, netdev->name, adapter);
> + igb_msix_other, IRQF_NO_THREAD, netdev->name, adapter);
> if (err)
> goto err_out;
>
This is scheduled for being reverted upstream [1]. Please drop from all
stable queues.
(credits go to Florian for pointing me to this rt-suspicious patch)
Jan
[1] https://lore.kernel.org/all/20241104124050.22290-1-wander@xxxxxxxxxx/
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