This is a note to let you know that I've just added the patch titled igb: Disable threaded IRQ for igb_msix_other to the 6.11-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: igb-disable-threaded-irq-for-igb_msix_other.patch and it can be found in the queue-6.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 052382490ee4f0f6d783ddce02fe6f2d15e134b5 Author: Wander Lairson Costa <wander@xxxxxxxxxx> Date: Mon Oct 21 16:26:24 2024 -0700 igb: Disable threaded IRQ for igb_msix_other [ 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> 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;