Messages in this thread Patch in this message | | | From | Eric Dumazet <> | Date | Fri, 17 Feb 2023 16:54:11 +0100 | Subject | Re: [RFC v2] net/core: add optional threading for rps backlog processing |
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On Fri, Feb 17, 2023 at 4:26 PM Felix Fietkau <nbd@nbd.name> wrote:
> > > Then, process_backlog() has been designed to run only from the cpu > > tied to the per-cpu data (softnet_data) > > There are multiple comments about this assumption, and various things > > that would need to be changed > > (eg sd_has_rps_ipi_waiting() would be wrong in its current implementation) > That's why I added the NAPI_STATE_THREADED check in napi_schedule_rps, > so that sd_has_rps_ipi_waiting would always return false. > Or are you worried about a race when enabling threading? >
Please look at all uses of sd->process_queue, without locking. They do not care about NAPI_STATE_THREADED
flush_backlog() is one instance, but process_backlog() is also using __skb_dequeue(&sd->process_queue)
I suspect the following patch would work today, and would show process_queue lock is not used.
diff --git a/net/core/dev.c b/net/core/dev.c index 5687b528d4c18ef2960edb6bf3161bbad666aece..bed540b417a1b4cd3e384611a4681b8e2a43fd30 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -11396,7 +11396,7 @@ static int __init net_dev_init(void) INIT_WORK(flush, flush_backlog);
skb_queue_head_init(&sd->input_pkt_queue); - skb_queue_head_init(&sd->process_queue); + __skb_queue_head_init(&sd->process_queue); #ifdef CONFIG_XFRM_OFFLOAD skb_queue_head_init(&sd->xfrm_backlog); #endif
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