On 2024-11-01 15:21:24 [-0400], Sasha Levin wrote: > 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. Wander, please send a revert of this patch. The ISR (E1000_ICR_TS set) may invoke igb_msg_task(), ptp_clock_event(), igb_perout(), igb_extts() each of which acquire sleeping locks on PREEMPT_RT. Not sure if this improved the situation or not. Sebastian
