[PATCH] net: ntb_netdev: Move ntb_netdev_rx_handler() to call netif_rx() from __netif_rx()

[PATCH] net: ntb_netdev: Move ntb_netdev_rx_handler() to call netif_rx() from __netif_rx()

[Dave Jiang]

The following is emitted when using idxd (DSA) dmanegine as the data
mover for ntb_transport that ntb_netdev uses.

[74412.546922] BUG: using smp_processor_id() in preemptible [00000000] code: irq/52-idxd-por/14526
[74412.556784] caller is netif_rx_internal+0x42/0x130
[74412.562282] CPU: 6 PID: 14526 Comm: irq/52-idxd-por Not tainted 6.9.5 #5
[74412.569870] Hardware name: Intel Corporation ArcherCity/ArcherCity, BIOS EGSDCRB1.E9I.1752.P05.2402080856 02/08/2024
[74412.581699] Call Trace:
[74412.584514]  <TASK>
[74412.586933]  dump_stack_lvl+0x55/0x70
[74412.591129]  check_preemption_disabled+0xc8/0xf0
[74412.596374]  netif_rx_internal+0x42/0x130
[74412.600957]  __netif_rx+0x20/0xd0
[74412.604743]  ntb_netdev_rx_handler+0x66/0x150 [ntb_netdev]
[74412.610985]  ntb_complete_rxc+0xed/0x140 [ntb_transport]
[74412.617010]  ntb_rx_copy_callback+0x53/0x80 [ntb_transport]
[74412.623332]  idxd_dma_complete_txd+0xe3/0x160 [idxd]
[74412.628963]  idxd_wq_thread+0x1a6/0x2b0 [idxd]
[74412.634046]  irq_thread_fn+0x21/0x60
[74412.638134]  ? irq_thread+0xa8/0x290
[74412.642218]  irq_thread+0x1a0/0x290
[74412.646212]  ? __pfx_irq_thread_fn+0x10/0x10
[74412.651071]  ? __pfx_irq_thread_dtor+0x10/0x10
[74412.656117]  ? __pfx_irq_thread+0x10/0x10
[74412.660686]  kthread+0x100/0x130
[74412.664384]  ? __pfx_kthread+0x10/0x10
[74412.668639]  ret_from_fork+0x31/0x50
[74412.672716]  ? __pfx_kthread+0x10/0x10
[74412.676978]  ret_from_fork_asm+0x1a/0x30
[74412.681457]  </TASK>

The cause is due to the idxd driver interrupt completion handler uses
threaded interrupt and the threaded handler is not hard or soft interrupt
context. However __netif_rx() can only be called from interrupt context.
Change the call to netif_rx() in order to allow completion via normal
context for dmaengine drivers that utilize threaded irq handling.

Fixes: baebdf48c360 ("net: dev: Makes sure netif_rx() can be invoked in any context.")
Reported-by: Jerry Dai <jerry.dai@intel.com>
Tested-by: Jerry Dai <jerry.dai@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
---
 drivers/net/ntb_netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ntb_netdev.c b/drivers/net/ntb_netdev.c
index 536bd6564f8b..dade51cf599c 100644
--- a/drivers/net/ntb_netdev.c
+++ b/drivers/net/ntb_netdev.c
@@ -119,7 +119,7 @@ static void ntb_netdev_rx_handler(struct ntb_transport_qp *qp, void *qp_data,
 	skb->protocol = eth_type_trans(skb, ndev);
 	skb->ip_summed = CHECKSUM_NONE;
 
-	if (__netif_rx(skb) == NET_RX_DROP) {
+	if (netif_rx(skb) == NET_RX_DROP) {
 		ndev->stats.rx_errors++;
 		ndev->stats.rx_dropped++;
 	} else {
-- 
2.45.1

Re: [PATCH] net: ntb_netdev: Move ntb_netdev_rx_handler() to call netif_rx() from __netif_rx()

[Jakub Kicinski]

On Wed, 26 Jun 2024 11:06:13 -0700 Dave Jiang wrote:
> Fixes: baebdf48c360 ("net: dev: Makes sure netif_rx() can be invoked in any context.")

Patch LGTM, but I think the Fixes tag needs to go back further.
Sebastian renamed and flipped semantics at the same time, so
what he did for this driver should be a noop.
IOW prior to his change netif_rx() expected to be called with
BH disabled, and the driver should have been using netif_rx_ni()
or netif_rx_any_context().
Maybe add this extra info to the commit message, there's also a way
to point out a dependency via a special tag..
But the Fixes tag should point to where the bug was introduced.
-- 
pw-bot: cr