Re: [PATCH net v3] xsk: freeze deferred pool teardown without blocking unregister

[Jason Xing]

On Wed, Oct 14, 2026 at 2:38 AM James Hilliard
<james.hilliard1@xxxxxxxxx> wrote:
>
> Deferred pool destruction calls ndo_bpf() under RTNL. system_wq is
> not frozen during system sleep, so that callback can run after a
> device has suspended and gated its clocks. Use system_freezable_wq
> so running destruction finishes before device suspend and new work
> waits until process thaw.
>
> Keep assigned pools visible to NETDEV_UNREGISTER independently of
> the socket list. A released socket has already left that list, but
> its final pool put can queue destruction after workqueues freeze.
> A resume-time unregister would then wait for a device reference
> whose release cannot run until the resume completes.
>
> Track assigned pools per netdev with netdev operations locking and detach
> remaining pools after the notifier socket walk, including copy-mode pools.
> This also covers leased queues without scanning pools from unrelated
> devices or network namespaces. Remove the entry on assignment failure and
> normal teardown. The deferred worker still owns the pool and later observes
> the cleared device pointer, avoiding a second driver detach or put.
>
> The lifetime problem was identified by code inspection of the deferred
> release and system-sleep paths.
>
> Fixes: 1c1efc2af158 ("xsk: Create and free buffer pool independently from umem")
> Signed-off-by: James Hilliard <james.hilliard1@xxxxxxxxx>

Admittedly it's a bit hard to review the complex logic. Thanks for the work!

Reviewed-by: Jason Xing <kerneljasonxing@xxxxxxxxx>