linux-kernel - Re: [Intel-wired-lan] [PATCH net] iavf: fix deadlock in reset handling

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Message-ID: <14cb0b22-ec39-43e4-a35b-22ad558b2e34@redhat.com>
Date: Tue, 3 Feb 2026 09:44:31 +0100
From: Petr Oros <poros@...hat.com>
To: Jacob Keller <jacob.e.keller@...el.com>, Jakub Kicinski <kuba@...nel.org>
Cc: ivecera@...hat.com, netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
 Andrew Lunn <andrew+netdev@...n.ch>, Eric Dumazet <edumazet@...gle.com>,
 Stanislav Fomichev <sdf@...ichev.me>,
 Tony Nguyen <anthony.l.nguyen@...el.com>,
 Przemek Kitszel <przemyslaw.kitszel@...el.com>,
 intel-wired-lan@...ts.osuosl.org, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>
Subject: Re: [Intel-wired-lan] [PATCH net] iavf: fix deadlock in reset
 handling

On 2/3/26 02:00, Jacob Keller wrote:
>
>
> On 2/2/2026 3:58 PM, Jakub Kicinski wrote:
>> On Mon,  2 Feb 2026 09:48:20 +0100 Petr Oros wrote:
>>> +    netdev_unlock(netdev);
>>> +    ret = wait_event_interruptible_timeout(adapter->reset_waitqueue,
>>> + !iavf_is_reset_in_progress(adapter),
>>> +                           msecs_to_jiffies(5000));
>>> +    netdev_lock(netdev);
>>
>> Dropping locks taken by the core around the driver callback
>> is obviously unacceptable. SMH.
>
> Right. It seems like the correct fix is to either a) have reset take 
> and hold the netdev lock (now that its distinct from the global RTNL 
> lock) or b) refactor reset so that it can defer any of the netdev 
> related stuff somehow.
>
I modeled this after the existing pattern in iavf_close() (ndo_stop), 
which also temporarily releases the netdev instance lock taken by the 
core to wait for an async operation to complete:

static int iavf_close(struct net_device *netdev)
{
         netdev_assert_locked(netdev);
         ...
         iavf_down(adapter);
         iavf_change_state(adapter, __IAVF_DOWN_PENDING);
         iavf_free_traffic_irqs(adapter);

         netdev_unlock(netdev);

         status = wait_event_timeout(adapter->down_waitqueue,
                                     adapter->state == __IAVF_DOWN,
                                     msecs_to_jiffies(500));
         if (!status)
                 netdev_warn(netdev, "Device resources not yet released\n");
         netdev_lock(netdev);
         ...
}

This was introduced by commit 120f28a6f314fe ("iavf: get rid of the crit 
lock"), and ndo_stop is called with netdev instance lock held by the 
core just like ndo_change_mtu is. Could you clarify why the 
unlock-wait-lock pattern is acceptable in ndo_stop but not here?