netdev - Re: [PATCH net] net: bridge: vlan: Add a schedule point during VLAN processing

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Date:   Thu, 30 Apr 2020 17:46:29 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     idosch@...sch.org
Cc:     netdev@...r.kernel.org, bridge@...ts.linux-foundation.org,
        kuba@...nel.org, nikolay@...ulusnetworks.com,
        roopa@...ulusnetworks.com, s.priebe@...fihost.ag,
        mlxsw@...lanox.com, idosch@...lanox.com
Subject: Re: [PATCH net] net: bridge: vlan: Add a schedule point during
 VLAN processing

From: Ido Schimmel <idosch@...sch.org>
Date: Thu, 30 Apr 2020 22:38:45 +0300

> From: Ido Schimmel <idosch@...lanox.com>
> 
> User space can request to delete a range of VLANs from a bridge slave in
> one netlink request. For each deleted VLAN the FDB needs to be traversed
> in order to flush all the affected entries.
> 
> If a large range of VLANs is deleted and the number of FDB entries is
> large or the FDB lock is contented, it is possible for the kernel to
> loop through the deleted VLANs for a long time. In case preemption is
> disabled, this can result in a soft lockup.
> 
> Fix this by adding a schedule point after each VLAN is deleted to yield
> the CPU, if needed. This is safe because the VLANs are traversed in
> process context.
> 
> Fixes: bdced7ef7838 ("bridge: support for multiple vlans and vlan ranges in setlink and dellink requests")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>
> Tested-by: Stefan Priebe - Profihost AG <s.priebe@...fihost.ag>

Applied and queued up for -stable.