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: Chain caused by macb_mac_link_up(): &bp->lock --> (softirq_ctrl.lock)

Chain caused by macb_start_xmit(): (softirq_ctrl.lock) --> _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.

Fixes: 633e98a711ac ("net: macb: use resolved link config in mac_link_up()") Cc: stable@vger.kernel.org Suggested-by: Kevin Hao kexin.hao@windriver.com Signed-off-by: Xiaolei Wang xiaolei.wang@windriver.com ---

V1: https://patchwork.kernel.org/project/netdevbpf/patch/20251128103647.351259-1... V2: Update the correct lock dependency chain and add the Fix tag.

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 ca2386b83473..064fccdcf699 100644 --- a/drivers/net/ethernet/cadence/macb_main.c +++ b/drivers/net/ethernet/cadence/macb_main.c @@ -744,7 +744,6 @@ 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) @@ -2991,6 +2990,8 @@ 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);