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Message-ID: <1a2b63a4-edc7-c04d-3f80-0087a8415bc3@candelatech.com>
Date: Thu, 26 Sep 2024 11:19:53 -0700
From: Ben Greear <greearb@...delatech.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, netdev@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH v2] Revert "vrf: Remove unnecessary RCU-bh critical
section"
On 9/26/24 02:03, Willem de Bruijn wrote:
> greearb@ wrote:
>> From: Ben Greear <greearb@...delatech.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@candelatech.com/T/
>>
>> Signed-off-by: Ben Greear <greearb@...delatech.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();
>> 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.
I was asked to add this, and also asked to CC stable.
Thanks,
Ben
--
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc http://www.candelatech.com
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