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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:
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.