> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-boun...@osuosl.org> On Behalf Of
> Wander Lairson Costa
> Sent: Wednesday, December 4, 2024 12:42 PM
> To: Nguyen, Anthony L <anthony.l.ngu...@intel.com>; Kitszel, Przemyslaw
> <przemyslaw.kits...@intel.com>; Andrew Lunn <andrew+net...@lunn.ch>;
> David S. Miller <da...@davemloft.net>; Eric Dumazet
> <eduma...@google.com>; Jakub Kicinski <k...@kernel.org>; Paolo Abeni
> <pab...@redhat.com>; Sebastian Andrzej Siewior <bige...@linutronix.de>; Clark
> Williams <clrkwl...@kernel.org>; Steven Rostedt <rost...@goodmis.org>; Auke
> Kok <auke-jan.h....@intel.com>; Jeff Garzik <jgar...@redhat.com>; moderated
> list:INTEL ETHERNET DRIVERS <intel-wired-...@lists.osuosl.org>; open
> list:NETWORKING DRIVERS <net...@vger.kernel.org>; open list <linux-
> ker...@vger.kernel.org>; open list:Real-time Linux
> (PREEMPT_RT):Keyword:PREEMPT_RT <linux-rt-de...@lists.linux.dev>
> Cc: Wander Lairson Costa <wan...@redhat.com>; Yuying Ma
> <y...@redhat.com>
> Subject: [Intel-wired-lan] [PATCH iwl-net 4/4] igb: fix igb_msix_other()
> handling
> for PREEMPT_RT
>
> 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.
>
> Commit 338c4d3902fe ("igb: Disable threaded IRQ for igb_msix_other") forced
> the ISR to run in a non-threaded context. However, Sebastian observed that
> some
> functions called within the ISR acquire locks that may sleep.
>
> In the previous two patches, we managed to make igb_msg_mask() safe to call
> from an interrupt context.
>
> In this commit, we move most of the ISR handling to an interrupt context,
> leaving
> non IRQ safe code to be called from the thread context under PREEMPT_RT.
>
> Reproducer:
>
> ipaddr_vlan=3
> nic_test=ens14f0
> vf=${nic_test}v0 # The main testing steps:
> while true; do
> ip link set ${nic_test} mtu 1500
> ip link set ${vf} mtu 1500
> ip link set $vf up
> # 3. set vlan and ip for VF
> 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}
> # 4. check the link state for VF and PF
> ip link show ${nic_test}
> if ! ip link show $vf | grep 'state UP'; then
> echo 'Error found'
> break
> fi
> ip link set $vf down
> done
>
> You can also reproduce it more reliably by setting nr_cpus=1 in the kernel
> command line.
>
> Fixes: 9d5c824399de ("igb: PCI-Express 82575 Gigabit Ethernet driver")
> Signed-off-by: Wander Lairson Costa <wan...@redhat.com>
> Reported-by: Yuying Ma <y...@redhat.com>
> ---
> drivers/net/ethernet/intel/igb/igb_main.c | 35 ++++++++++++++++-------
> 1 file changed, 24 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> b/drivers/net/ethernet/intel/igb/igb_main.c
> index 5828831fd29c2..b2894cebe2c9e 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -131,6 +131,7 @@ static void igb_set_uta(struct igb_adapter *adapter, bool
Tested-by: Rafal Romanowski <rafal.romanow...@intel.com>
