Subject: Re: [PATCH net-next v4 1/5] net: sched: introduce qdisc-specific drop reason tracing

From: Jakub Kicinski <[email-masked]>
Date: Tue, 17 Feb 2026 16:34:08 -0800

On Mon, 16 Feb 2026 16:30:29 +0100 Jesper Dangaard Brouer wrote:
> Create new enum qdisc_drop_reason and trace_qdisc_drop tracepoint
> for qdisc layer drop diagnostics with direct qdisc context visibility.
> 
> The new tracepoint includes qdisc handle, parent, kind (name), and
> device information. Existing SKB_DROP_REASON_QDISC_DROP is retained
> for backwards compatibility via kfree_skb_reason().
> 
> Convert qdiscs with drop reasons to use the new infrastructure.
> 
> Change CAKE's cobalt_should_drop() return type from enum skb_drop_reason
> to enum qdisc_drop_reason to fix implicit enum conversion warnings.
> Use QDISC_DROP_UNSPEC as the 'not dropped' sentinel instead of
> SKB_NOT_DROPPED_YET. Both have the same compiled value (0), so the
> comparison logic remains semantically equivalent.

net/sched/sch_dualpi2.c:594:12: warning: implicit conversion from enumeration type 'enum qdisc_drop_reason' to different enumeration type 'enum skb_drop_reason' [-Wimplicit-enum-enum-cast]
  593 |                         drop_and_retry(q, skb, sch,
      |                         ~~~~~~~~~~~~~~
  594 |                                        QDISC_DROP_CONGESTED);
      |                                        ^~~~~~~~~~~~~~~~~~~~
-- 
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