netdev - Re: [PATCH net 0/3] net: core: fix a lockdep splat in the dev_addr

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Message-Id: <20200928.151410.232993869895631044.davem@davemloft.net>
Date:   Mon, 28 Sep 2020 15:14:10 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     ap420073@...il.com
Cc:     kuba@...nel.org, netdev@...r.kernel.org, xiyou.wangcong@...il.com
Subject: Re: [PATCH net 0/3] net: core: fix a lockdep splat in the
 dev_addr_list.

From: Taehee Yoo <ap420073@...il.com>
Date: Fri, 25 Sep 2020 18:12:46 +0000

> This patchset is to avoid lockdep splat.
> 
> When a stacked interface graph is changed, netif_addr_lock() is called
> recursively and it internally calls spin_lock_nested().
> The parameter of spin_lock_nested() is 'dev->lower_level',
> this is called subclass.
> The problem of 'dev->lower_level' is that while 'dev->lower_level' is
> being used as a subclass of spin_lock_nested(), its value can be changed.
> So, spin_lock_nested() would be called recursively with the same
> subclass value, the lockdep understands a deadlock.
> In order to avoid this, a new variable is needed and it is going to be
> used as a parameter of spin_lock_nested().
> The first and second patch is a preparation patch for the third patch.
> In the third patch, the problem will be fixed.
> 
> The first patch is to add __netdev_upper_dev_unlink().
> An existed netdev_upper_dev_unlink() is renamed to
> __netdev_upper_dev_unlink(). and netdev_upper_dev_unlink()
> is added as an wrapper of this function.
> 
> The second patch is to add the netdev_nested_priv structure.
> netdev_walk_all_{ upper | lower }_dev() pass both private functions
> and "data" pointer to handle their own things.
> At this point, the data pointer type is void *.
> In order to make it easier to expand common variables and functions,
> this new netdev_nested_priv structure is added.
> 
> The third patch is to add a new variable 'nested_level'
> into the net_device structure.
> This variable will be used as a parameter of spin_lock_nested() of
> dev->addr_list_lock.
> Due to this variable, it can avoid lockdep splat.

Series applied, thank you.