diff mbox series

[net,1/3] igb: Disable threaded IRQ for igb_msix_other

Message ID 20241021-iwl-2024-10-21-iwl-net-fixes-v1-1-a50cb3059f55@intel.com (mailing list archive)
State Accepted
Commit 338c4d3902feb5be49bfda530a72c7ab860e2c9f
Delegated to: Netdev Maintainers
Headers show
Series Intel Wired LAN Driver Fixes 2024-10-21 (igb, ice) | expand

Checks

Context Check Description
netdev/series_format success Posting correctly formatted
netdev/tree_selection success Clearly marked for net
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag present in non-next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 5 this patch: 5
netdev/build_tools success No tools touched, skip
netdev/cc_maintainers warning 2 maintainers not CCed: anthony.l.nguyen@intel.com intel-wired-lan@lists.osuosl.org
netdev/build_clang success Errors and warnings before: 3 this patch: 3
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 Fixes tag looks correct
netdev/build_allmodconfig_warn success Errors and warnings before: 4 this patch: 4
netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns
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

Jacob Keller Oct. 21, 2024, 11:26 p.m. UTC 
From: Wander Lairson Costa <wander@redhat.com>

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@redhat.com>
Fixes: 9d5c824399de ("igb: PCI-Express 82575 Gigabit Ethernet driver")
Reported-by: Yuying Ma <yuma@redhat.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Simon Horman Oct. 24, 2024, 8:47 a.m. UTC | #1 
On Mon, Oct 21, 2024 at 04:26:24PM -0700, Jacob Keller wrote:
> From: Wander Lairson Costa <wander@redhat.com>
> 
> 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@redhat.com>
> Fixes: 9d5c824399de ("igb: PCI-Express 82575 Gigabit Ethernet driver")
> Reported-by: Yuying Ma <yuma@redhat.com>
> Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
> Tested-by: Rafal Romanowski <rafal.romanowski@intel.com>
> Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>

Reviewed-by: Simon Horman <horms@kernel.org>
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 f1d088168723..b83df5f94b1f 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;