Subject: Re: [Intel-wired-lan] [PATCH 1/1 iwl-net] idpf: disable local BH when scheduling napi for marker packets

From: Alexander Lobakin <[email-masked]>
Date: Mon, 12 Feb 2024 15:41:21 +0100

From: Alan Brady <[email-masked]>
Date: Wed,  7 Feb 2024 16:42:43 -0800

> From: Emil Tantilov <[email-masked]>
> 
> Fix softirq's not being handled during napi_schedule() call when
> receiving marker packets for queue disable by disabling local bottom
> half.
> 
> The issue can be seen on ifdown:
> NOHZ tick-stop error: Non-RCU local softirq work is pending, handler #08!!!
> 
> Using ftrace to catch the failing scenario:
> ifconfig   [003] d.... 22739.830624: softirq_raise: vec=3 [action=NET_RX]
> <idle>-0   [003] ..s.. 22739.831357: softirq_entry: vec=3 [action=NET_RX]
> 
> No interrupt and CPU is idle.
> 
> After the patch, with BH locks:

Minor: local_bh_{en,dis}able() are not "BH locks", it's BH
enabling/disabling. It doesn't lock/unlock anything.

> ifconfig   [003] d.... 22993.928336: softirq_raise: vec=3 [action=NET_RX]
> ifconfig   [003] ..s1. 22993.928337: softirq_entry: vec=3 [action=NET_RX]
> 
> Fixes: c2d548cad150 ("idpf: add TX splitq napi poll support")
> Reviewed-by: Jesse Brandeburg <[email-masked]>
> Reviewed-by: Przemek Kitszel <[email-masked]>
> Signed-off-by: Emil Tantilov <[email-masked]>
> Signed-off-by: Alan Brady <[email-masked]>

Thanks,
Olek