[net PATCH] net: macb: Relocate mog_init_rings() callback from macb_mac_link_up() to macb_open()

Xiaolei Wang
2025-11-28T10:37:30Z

In the non-RT kernel, local_bh_disable() merely disables preemption,
whereas it maps to an actual spin lock in the RT kernel. Consequently,
when attempting to refill RX buffers via netdev_alloc_skb() in
macb_mac_link_up(), a deadlock scenario arises as follows:
The dependency chain caused by macb_mac_link_up():
&bp->lock --> (softirq_ctrl.lock) --> _xmit_ETHER#2

The dependency chain caused by macb_start_xmit():
_xmit_ETHER#2 --> &bp->lock

Notably, invoking the mog_init_rings() callback upon link establishment
is unnecessary. Instead, we can exclusively call mog_init_rings() within
the ndo_open() callback. This adjustment resolves the deadlock issue.
Given that mog_init_rings() is only applicable to
non-MACB_CAPS_MACB_IS_EMAC cases, we can simply move it to macb_open()
and simultaneously eliminate the MACB_CAPS_MACB_IS_EMAC check.

Suggested-by: Kevin Hao <kexin.hao@windriver.com>
Signed-off-by: Xiaolei Wang <xiaolei.wang@windriver.com>
---
drivers/net/ethernet/cadence/macb_main.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index 65bc73f6fa30..7df2ad093bab 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -775,7 +775,6 @@ static void macb_mac_link_up(struct phylink_config *config,
/* Initialize rings & buffers as clearing MACB_BIT(TE) in link down
* cleared the pipeline and control registers.
*/
- bp->macbgem_ops.mog_init_rings(bp);
macb_init_buffers(bp);

for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue)
@@ -3049,6 +3048,8 @@ static int macb_open(struct net_device *dev)
goto pm_exit;
}

+ bp->macbgem_ops.mog_init_rings(bp);
+
for (q = 0, queue = bp->queues; q < bp->num_queues; ++q, ++queue) {
napi_enable(&queue->napi_rx);
napi_enable(&queue->napi_tx);
--
2.43.0