From: Jakub Kicinski kuba@kernel.org
commit afbed3f74830163f9559579dee382cac3cff82da upstream.
NAPI gets called with budget of 0 from netpoll, which has interrupts disabled. We should try to free some space on Tx rings and nothing else.
Specifically do not try to handle XDP TX or try to refill Rx buffers - we can't use the page pool from IRQ context. Don't check if IRQs moved, either, that makes no sense in netpoll. Netpoll calls _all_ the rings from whatever CPU it happens to be invoked on.
In general do as little as possible, the work quickly adds up when there's tens of rings to poll.
The immediate stack trace I was seeing is:
__do_softirq+0xd1/0x2c0 __local_bh_enable_ip+0xc7/0x120 </IRQ> <TASK> page_pool_put_defragged_page+0x267/0x320 mlx5e_free_xdpsq_desc+0x99/0xd0 mlx5e_poll_xdpsq_cq+0x138/0x3b0 mlx5e_napi_poll+0xc3/0x8b0 netpoll_poll_dev+0xce/0x150
AFAIU page pool takes a BH lock, releases it and since BH is now enabled tries to run softirqs.
Reviewed-by: Tariq Toukan tariqt@nvidia.com Fixes: 60bbf7eeef10 ("mlx5: use page_pool for xdp_return_frame call") Signed-off-by: Jakub Kicinski kuba@kernel.org Reviewed-by: Simon Horman simon.horman@corigine.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
--- a/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c +++ b/drivers/net/ethernet/mellanox/mlx5/core/en_txrx.c @@ -150,20 +150,22 @@ int mlx5e_napi_poll(struct napi_struct * } }
+ /* budget=0 means we may be in IRQ context, do as little as possible */ + if (unlikely(!budget)) + goto out; + busy |= mlx5e_poll_xdpsq_cq(&c->xdpsq.cq);
if (c->xdp) busy |= mlx5e_poll_xdpsq_cq(&c->rq_xdpsq.cq);
- if (likely(budget)) { /* budget=0 means: don't poll rx rings */ - if (xsk_open) - work_done = mlx5e_poll_rx_cq(&xskrq->cq, budget); + if (xsk_open) + work_done = mlx5e_poll_rx_cq(&xskrq->cq, budget);
- if (likely(budget - work_done)) - work_done += mlx5e_poll_rx_cq(&rq->cq, budget - work_done); + if (likely(budget - work_done)) + work_done += mlx5e_poll_rx_cq(&rq->cq, budget - work_done);
- busy |= work_done == budget; - } + busy |= work_done == budget;
mlx5e_poll_ico_cq(&c->icosq.cq); if (mlx5e_poll_ico_cq(&c->async_icosq.cq))