quoted

Well, it does complain (report below), but I'm not sure it's related.
The other thing I tried was the AF_XDP example here:
https://github.com/xdp-project/xdp-tutorial/tree/master/advanced03-AF_XDP

With this example poll() always seems to block correctly, so I think
maybe there is something wrong with the xdpsock_user.c example or how
I'm using it.

[  259.591480] BUG: assuming atomic context at net/core/ptp_classifier.c:106
[  259.591488] in_atomic(): 0, irqs_disabled(): 0, pid: 953, name: irq/22-eth%d
[  259.591494] CPU: 0 PID: 953 Comm: irq/22-eth%d Tainted: G        WC
       5.

                        2.21-rt13-00016-g93898e751d0e #90
[  259.591499] Hardware name: Enclustra XU5 SOM (DT)
[  259.591501] Call trace:
[  259.591503] dump_backtrace (/arch/arm64/kernel/traps.c:94)
[  259.591514] show_stack (/arch/arm64/kernel/traps.c:151)
[  259.591520] dump_stack (/lib/dump_stack.c:115)
[  259.591526] __cant_sleep (/kernel/sched/core.c:6386)
[  259.591531] ptp_classify_raw (/./include/linux/compiler.h:194

Is this the only splat? Nothing more? I would expect something at boot
time, too.

I should have expanded more. This seems to happen every second
starting at boot in ptp_classifier.c regardless of if I'm doing
anything with BPF.

So this part expects disabled preemption. Other invocations disable
preemption. The whole BPF part is currently not working on -RT.

OK, so I should expect more issues as we play with AF_XDP? An
application based on the other example [1] is at least running.
Preempt-rt + AF_XDP seems like an awesome combination, so I hopefully
any BPF issues can be resolved.

thanks,
Paul

[1] https://github.com/xdp-project/xdp-tutorial/tree/master/advanced03-AF_XDP