Commit e88a2766 authored Nov 14, 2016 by Eric Dumazet Committed by David S. Miller Nov 15, 2016

gro_cells: mark napi struct as not busy poll candidates



Rolf Neugebauer reported very long delays at netns dismantle.

Eric W. Biederman was kind enough to look at this problem
and noticed synchronize_net() occurring from netif_napi_del() that was
added in linux-4.5

Busy polling makes no sense for tunnels NAPI.
If busy poll is used for sessions over tunnels, the poller will need to
poll the physical device queue anyway.

netif_tx_napi_add() could be used here, but function name is misleading,
and renaming it is not stable material, so set NAPI_STATE_NO_BUSY_POLL
bit directly.

This will avoid inserting gro_cells napi structures in napi_hash[]
and avoid the problematic synchronize_net() (per possible cpu) that
Rolf reported.

Fixes: 93d05d4a ("net: provide generic busy polling to all NAPI drivers")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Reported-by: Eric W. Biederman <ebiederm@xmission.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Tested-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 73e2d5e3

include/net/gro_cells.h

+3 −0

Original line number	Diff line number	Diff line
		@@ -68,6 +68,9 @@ static inline int gro_cells_init(struct gro_cells gcells, struct net_device de
		struct gro_cell *cell = per_cpu_ptr(gcells->cells, i);

		__skb_queue_head_init(&cell->napi_skbs);

		set_bit(NAPI_STATE_NO_BUSY_POLL, &cell->napi.state);

		netif_napi_add(dev, &cell->napi, gro_cell_poll, 64);
		napi_enable(&cell->napi);
		}

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