[PATCH net repost] nfp: do not update MTU from BH in flower app

[PATCH net repost] nfp: do not update MTU from BH in flower app

[Simon Horman]

The Flower app may receive a request to update the MTU of a representor
netdev upon receipt of a control message from the firmware. This requires
the RTNL lock which needs to be taken outside of the packet processing
path.

As a handling of this correctly seems a little to invasive for a fix simply
skip setting the MTU for now.

Relevant backtrace:
 [ 1496.288489] BUG: scheduling while atomic: kworker/0:3/373/0x00000100
 [ 1496.294911]  dca syscopyarea sysfillrect sysimgblt fb_sys_fops ptp drm mxm_wmi ahci pps_core libahci i2c_algo_bit wmi [last unloaded: nfp]
 [ 1496.294918] CPU: 0 PID: 373 Comm: kworker/0:3 Tainted: G           OE   4.13.0-rc3+ #3
 [ 1496.294919] Hardware name: Supermicro X10DRi/X10DRi, BIOS 2.0 12/28/2015
 [ 1496.294923] Workqueue: events work_for_cpu_fn
 [ 1496.294924] Call Trace:
 [ 1496.294927]  <IRQ>
 [ 1496.294931]  dump_stack+0x63/0x82
 [ 1496.294935]  __schedule_bug+0x54/0x70
 [ 1496.294937]  __schedule+0x62f/0x890
 [ 1496.294941]  ? intel_unmap_sg+0x90/0x90
 [ 1496.294942]  schedule+0x36/0x80
 [ 1496.294943]  schedule_preempt_disabled+0xe/0x10
 [ 1496.294945]  __mutex_lock.isra.2+0x445/0x4a0
 [ 1496.294947]  ? device_is_rmrr_locked+0x12/0x50
 [ 1496.294950]  ? kfree+0x162/0x170
 [ 1496.294952]  ? device_is_rmrr_locked+0x12/0x50
 [ 1496.294953]  ? iommu_should_identity_map+0x50/0xe0
 [ 1496.294954]  __mutex_lock_slowpath+0x13/0x20
 [ 1496.294955]  ? iommu_no_mapping+0x48/0xd0
 [ 1496.294956]  ? __mutex_lock_slowpath+0x13/0x20
 [ 1496.294957]  mutex_lock+0x2f/0x40
 [ 1496.294960]  rtnl_lock+0x15/0x20
 [ 1496.294979]  nfp_flower_cmsg_rx+0xc8/0x150 [nfp]
 [ 1496.294986]  nfp_ctrl_poll+0x286/0x350 [nfp]
 [ 1496.294989]  tasklet_action+0xf6/0x110
 [ 1496.294992]  __do_softirq+0xed/0x278
 [ 1496.294993]  irq_exit+0xb6/0xc0
 [ 1496.294994]  do_IRQ+0x4f/0xd0
 [ 1496.294996]  common_interrupt+0x89/0x89

Fixes: 948faa46c05b ("nfp: add support for control messages for flower app")
Signed-off-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
---
 drivers/net/ethernet/netronome/nfp/flower/cmsg.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/netronome/nfp/flower/cmsg.c b/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
index dd7fa9cf225f..b0837b58c3a1 100644
--- a/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
+++ b/drivers/net/ethernet/netronome/nfp/flower/cmsg.c
@@ -115,14 +115,10 @@ nfp_flower_cmsg_portmod_rx(struct nfp_app *app, struct sk_buff *skb)
 		return;
 	}
 
-	if (link) {
+	if (link)
 		netif_carrier_on(netdev);
-		rtnl_lock();
-		dev_set_mtu(netdev, be16_to_cpu(msg->mtu));
-		rtnl_unlock();
-	} else {
+	else
 		netif_carrier_off(netdev);
-	}
 	rcu_read_unlock();
 }
 
-- 
2.1.4

Re: [PATCH net repost] nfp: do not update MTU from BH in flower app

[David Miller]

From: Simon Horman <simon.horman@netronome.com>
Date: Fri, 11 Aug 2017 10:18:20 +0200

> The Flower app may receive a request to update the MTU of a representor
> netdev upon receipt of a control message from the firmware. This requires
> the RTNL lock which needs to be taken outside of the packet processing
> path.
> 
> As a handling of this correctly seems a little to invasive for a fix simply
> skip setting the MTU for now.
> 
> Relevant backtrace:
 ...
> Fixes: 948faa46c05b ("nfp: add support for control messages for flower app")
> Signed-off-by: Simon Horman <simon.horman@netronome.com>
> Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>

Applied.

Re: [PATCH net repost] nfp: do not update MTU from BH in flower app

[Simon Horman]

On Fri, Aug 11, 2017 at 02:51:07PM -0700, David Miller wrote:
> From: Simon Horman <simon.horman@netronome.com>
> Date: Fri, 11 Aug 2017 10:18:20 +0200
> 
> > The Flower app may receive a request to update the MTU of a representor
> > netdev upon receipt of a control message from the firmware. This requires
> > the RTNL lock which needs to be taken outside of the packet processing
> > path.
> > 
> > As a handling of this correctly seems a little to invasive for a fix simply
> > skip setting the MTU for now.
> > 
> > Relevant backtrace:
>  ...
> > Fixes: 948faa46c05b ("nfp: add support for control messages for flower app")
> > Signed-off-by: Simon Horman <simon.horman@netronome.com>
> > Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> 
> Applied.

Thanks.

Could you pull net into net-next? I'd like to send up a follow-up
for net-next to allow processing of the MTU.

Re: [PATCH net repost] nfp: do not update MTU from BH in flower app

[David Miller]

From: Simon Horman <simon.horman@netronome.com>
Date: Tue, 15 Aug 2017 08:13:48 +0200

> Could you pull net into net-next? I'd like to send up a follow-up
> for net-next to allow processing of the MTU.

Once Linus takes the pull request I just sent to him, I will
do this.

Re: [PATCH net repost] nfp: do not update MTU from BH in flower app

[David Miller]

From: David Miller <davem@davemloft.net>
Date: Tue, 15 Aug 2017 17:52:40 -0700 (PDT)

> From: Simon Horman <simon.horman@netronome.com>
> Date: Tue, 15 Aug 2017 08:13:48 +0200
> 
>> Could you pull net into net-next? I'd like to send up a follow-up
>> for net-next to allow processing of the MTU.
> 
> Once Linus takes the pull request I just sent to him, I will
> do this.

And this is now done.

Re: [PATCH net repost] nfp: do not update MTU from BH in flower app

[Simon Horman]

On Tue, Aug 15, 2017 at 09:03:58PM -0700, David Miller wrote:
> From: David Miller <davem@davemloft.net>
> Date: Tue, 15 Aug 2017 17:52:40 -0700 (PDT)
> 
> > From: Simon Horman <simon.horman@netronome.com>
> > Date: Tue, 15 Aug 2017 08:13:48 +0200
> > 
> >> Could you pull net into net-next? I'd like to send up a follow-up
> >> for net-next to allow processing of the MTU.
> > 
> > Once Linus takes the pull request I just sent to him, I will
> > do this.
> 
> And this is now done.

Great, thanks.