This is a note to let you know that I've just added the patch titled
net/mlx5e: do as little as possible in napi poll when budget is 0
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-mlx5e-do-as-little-as-possible-in-napi-poll-when-budget-is-0.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From afbed3f74830163f9559579dee382cac3cff82da Mon Sep 17 00:00:00 2001
From: Jakub Kicinski <kuba@xxxxxxxxxx>
Date: Tue, 16 May 2023 18:59:35 -0700
Subject: net/mlx5e: do as little as possible in napi poll when budget is 0
From: Jakub Kicinski <kuba@xxxxxxxxxx>
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@xxxxxxxxxx>
Fixes: 60bbf7eeef10 ("mlx5: use page_pool for xdp_return_frame call")
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Reviewed-by: Simon Horman <simon.horman@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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))
Patches currently in stable-queue which might be from kuba@xxxxxxxxxx are
queue-5.15/forcedeth-fix-an-error-handling-path-in-nv_probe.patch
queue-5.15/net-fix-skb-leak-in-__skb_tstamp_tx.patch
queue-5.15/net-fix-stack-overflow-when-lro-is-disabled-for-virtual-interfaces.patch
queue-5.15/net-mlx5e-do-as-little-as-possible-in-napi-poll-when-budget-is-0.patch
queue-5.15/net-cdc_ncm-deal-with-too-low-values-of-dwntboutmaxsize.patch
