Re: [PATCH net v2] xsk: freeze deferred pool teardown without blocking unregister

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 under RTNL 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 <redacted>
---
Changes in v2:
- Track assigned pools per netdev instead of scanning a global pool list.
- Keep deferred releases visible across queue changes and queue leases.
- Rebase onto current net.
- Link to v1: https://patch.msgid.link/20260930-xsk-suspend-teardown-v1-1-a6cac8c030be@gmail.com (local)

To: "David S. Miller" <davem@davemloft.net>
To: Eric Dumazet <edumazet@kernel.org>
To: Jakub Kicinski <kuba@kernel.org>
To: Paolo Abeni <pabeni@redhat.com>
To: Simon Horman <horms@kernel.org>
To: Andrew Lunn <andrew+netdev@lunn.ch>
To: Magnus Karlsson <magnus.karlsson@intel.com>
To: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
To: Stanislav Fomichev <sdf@fomichev.me>
To: Alexei Starovoitov <ast@kernel.org>
To: Daniel Borkmann <daniel@iogearbox.net>
To: Jesper Dangaard Brouer <hawk@kernel.org>
To: John Fastabend <john.fastabend@gmail.com>
To: Björn Töpel <bjorn@kernel.org>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: bpf@vger.kernel.org
---
 include/linux/netdevice.h   |  5 +++++
 include/net/xsk_buff_pool.h |  3 +++
 net/xdp/xsk.c               |  5 +++++
 net/xdp/xsk_buff_pool.c     | 25 ++++++++++++++++++++++++-
 4 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3cff2174dc03..72091938f6e6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h

@@ -2545,6 +2545,11 @@ struct net_device {
 	/* protected by rtnl_lock */
 	struct bpf_xdp_entity	xdp_state[__MAX_XDP_MODE];
 
+#ifdef CONFIG_XDP_SOCKETS
+	/** @xsk_pools: assigned AF_XDP pools, protected by rtnl_lock */