[PATCHv2 net] net: thunderx: use spin_lock_bh in nicvf_set_rx_mode_task()

[David Miller]

From: Xin Long <lucien.xin at gmail.com>
Date: Tue,  4 Aug 2020 15:02:30 +0800

> A dead lock was triggered on thunderx driver:
> 
>         CPU0                    CPU1
>         ----                    ----
>    [01] lock(&(&nic->rx_mode_wq_lock)->rlock);
>                            [11] lock(&(&mc->mca_lock)->rlock);
>                            [12] lock(&(&nic->rx_mode_wq_lock)->rlock);
>    [02] <Interrupt> lock(&(&mc->mca_lock)->rlock);
> 
> The path for each is:
> 
>   [01] worker_thread() -> process_one_work() -> nicvf_set_rx_mode_task()
>   [02] mld_ifc_timer_expire()
>   [11] ipv6_add_dev() -> ipv6_dev_mc_inc() -> igmp6_group_added() ->
>   [12] dev_mc_add() -> __dev_set_rx_mode() -> nicvf_set_rx_mode()
> 
> To fix it, it needs to disable bh on [1], so that the timer on [2]
> wouldn't be triggered until rx_mode_wq_lock is released. So change
> to use spin_lock_bh() instead of spin_lock().
> 
> Thanks to Paolo for helping with this.
> 
> v1->v2:
>   - post to netdev.
> 
> Reported-by: Rafael P. <rparrazo at redhat.com>
> Tested-by: Dean Nelson <dnelson at redhat.com>
> Fixes: 469998c861fa ("net: thunderx: prevent concurrent data re-writing by nicvf_set_rx_mode")
> Signed-off-by: Xin Long <lucien.xin at gmail.com>

Applied and queued up for -stable, thank you.