netdev - Re: [PATCH] igb: revert rtnl_lock() that causes deadlock

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Date:   Tue, 7 Mar 2023 14:45:02 +0100
From:   Corinna Vinschen <vinschen@...hat.com>
To:     Lin Ma <linma@....edu.cn>
Cc:     jesse.brandeburg@...el.com, anthony.l.nguyen@...el.com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, richardcochran@...il.com,
        ast@...nel.org, daniel@...earbox.net, hawk@...nel.org,
        john.fastabend@...il.com, intel-wired-lan@...ts.osuosl.org,
        pmenzel@...gen.mpg.de, regressions@...ts.linux.dev,
        stable@...r.kernel.org
Subject: Re: [PATCH] igb: revert rtnl_lock() that causes deadlock

On Mar  7 21:05, Lin Ma wrote:
> The commit 6faee3d4ee8b ("igb: Add lock to avoid data race") adds
> rtnl_lock to eliminate a false data race shown below
> 
>  (FREE from device detaching)      |   (USE from netdev core)
> igb_remove                         |  igb_ndo_get_vf_config
>  igb_disable_sriov                 |  vf >= adapter->vfs_allocated_count?
>   kfree(adapter->vf_data)          |
>   adapter->vfs_allocated_count = 0 |
>                                    |    memcpy(... adapter->vf_data[vf]
> 
> The above race will never happen and the extra rtnl_lock causes deadlock
> below
> [...]
> CC: stable@...r.kernel.org
> Fixes: 6faee3d4ee8b ("igb: Add lock to avoid data race")
> Reported-by: Corinna <vinschen@...hat.com>

Thank you, but "Corinna Vinschen", please.


Thanks,
Corinna