greearb@ wrote:
> From: Ben Greear <greearb@xxxxxxxxxxxxxxx>
>
> This reverts commit 504fc6f4f7f681d2a03aa5f68aad549d90eab853.
>
> dev_queue_xmit_nit needs to run with bh locking, otherwise
> it conflicts with packets coming in from a nic in softirq
> context and packets being transmitted from user context.
>
> ================================
> WARNING: inconsistent lock state
> 6.11.0 #1 Tainted: G W
> --------------------------------
> inconsistent {IN-SOFTIRQ-W} -> {SOFTIRQ-ON-W} usage.
> btserver/134819 [HC0[0]:SC0[0]:HE1:SE1] takes:
> ffff8882da30c118 (rlock-AF_PACKET){+.?.}-{2:2}, at: tpacket_rcv+0x863/0x3b30
> {IN-SOFTIRQ-W} state was registered at:
> lock_acquire+0x19a/0x4f0
> _raw_spin_lock+0x27/0x40
> packet_rcv+0xa33/0x1320
> __netif_receive_skb_core.constprop.0+0xcb0/0x3a90
> __netif_receive_skb_list_core+0x2c9/0x890
> netif_receive_skb_list_internal+0x610/0xcc0
> napi_complete_done+0x1c0/0x7c0
> igb_poll+0x1dbb/0x57e0 [igb]
> __napi_poll.constprop.0+0x99/0x430
> net_rx_action+0x8e7/0xe10
> handle_softirqs+0x1b7/0x800
> __irq_exit_rcu+0x91/0xc0
> irq_exit_rcu+0x5/0x10
> [snip]
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(rlock-AF_PACKET);
> <Interrupt>
> lock(rlock-AF_PACKET);
>
> *** DEADLOCK ***
>
> Call Trace:
> <TASK>
> dump_stack_lvl+0x73/0xa0
> mark_lock+0x102e/0x16b0
> __lock_acquire+0x9ae/0x6170
> lock_acquire+0x19a/0x4f0
> _raw_spin_lock+0x27/0x40
> tpacket_rcv+0x863/0x3b30
> dev_queue_xmit_nit+0x709/0xa40
> vrf_finish_direct+0x26e/0x340 [vrf]
> vrf_l3_out+0x5f4/0xe80 [vrf]
> __ip_local_out+0x51e/0x7a0
> [snip]
>
> Fixes: 504fc6f4f7f6 ("vrf: Remove unnecessary RCU-bh critical section")
> Link: https://lore.kernel.org/netdev/05765015-f727-2f30-58da-2ad6fa7ea99f@xxxxxxxxxxxxxxx/T/
>
> Signed-off-by: Ben Greear <greearb@xxxxxxxxxxxxxxx>
Please Cc: all previous reviewers and folks who participated in the
discussion. I entirely missed this. No need to add as Cc tags, just
--cc in git send-email will do.
> ---
>
> v2: Edit patch description.
>
> drivers/net/vrf.c | 2 ++
> net/core/dev.c | 1 +
> 2 files changed, 3 insertions(+)
>
> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
> index 4d8ccaf9a2b4..4087f72f0d2b 100644
> --- a/drivers/net/vrf.c
> +++ b/drivers/net/vrf.c
> @@ -608,7 +608,9 @@ static void vrf_finish_direct(struct sk_buff *skb)
> eth_zero_addr(eth->h_dest);
> eth->h_proto = skb->protocol;
>
> + rcu_read_lock_bh();
> dev_queue_xmit_nit(skb, vrf_dev);
> + rcu_read_unlock_bh();
>
> skb_pull(skb, ETH_HLEN);
> }
> diff --git a/net/core/dev.c b/net/core/dev.c
> index cd479f5f22f6..566e69a38eed 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -2285,6 +2285,7 @@ EXPORT_SYMBOL_GPL(dev_nit_active);
> /*
> * Support routine. Sends outgoing frames to any network
> * taps currently in use.
> + * BH must be disabled before calling this.
Unnecessary. Especially patches for stable should be minimal to
reduce the chance of conflicts.
