Re: [PATCH v2] net: iterate online nodes in skb_defer_free_flush()

[Eric Dumazet]

On Tue, Sep 15, 2026 at 4:56 PM Kris Pan <kris.pan@xxxxxxxxx> wrote:
>
> Right, the node-offline race is real.  I'll fix it in a v3 so the flush
> doesn't depend on node_online_map, e.g. a per-CPU mask of pending nodes
> set by the producer and drained by the flush.

Certainly not.

We should not add a per-CPU active-node bitmask updated by
skb_attempt_defer_free(),
as writing to a shared bitmask from remote CPUs would re-introduce the
cross-NUMA
cache line bouncing that commit 5628f3fe3b16 eliminated.

Instead, keep for_each_online_node(node) in the skb_defer_free_flush()
fast path,
and handle cleanup in the cold dev_cpu_dead(unsigned int oldcpu) hotplug path.