Ben Greear wrote:
On 9/26/24 02:03, Willem de Bruijn wrote:
greearb@ wrote:
From: Ben Greear greearb@candelatech.com
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@candelat...
Signed-off-by: Ben Greear greearb@candelatech.com
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();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.
I was asked to add this, and also asked to CC stable.
Conflicting feedback is annoying, but I disagree with the other comment.
Not only does it potentially complicate backporting, it also is no longer a strict revert. In which case it must not be labeled as such.
Easier is to keep the revert unmodified, and add the comment to the commit message.
Most important is the Link to our earlier thread that explains the history.
If the process appears byzantine, if you prefer I can also send it.
Thanks,
Willem