On 9/20/24 20:59, Wander Lairson Costa wrote:
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 <wan...@redhat.com> Reported-by: Yuying Ma <y...@redhat.com> --- 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 1ef4cb871452..8a1696d7289f 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;
Thank you for small, localized fix with a good description. Our VAL will check it also on non-RT OS. Reviewed-by: Przemek Kitszel <przemyslaw.kits...@intel.com> PS: for future intel ethernet submissions please split out fixes and refactors, and tag each commit with the [iwl-net] or [iwl-next] tags
