netdev - Re: [PATCH net-next] net: Write lock dev_base_lock without disabling bottom halves.

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Date:   Mon, 29 Nov 2021 12:20:10 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     netdev@...r.kernel.org, lgoncalv@...hat.com, rostedt@...dmis.org,
        nilal@...hat.com, pezhang@...hat.com, davem@...emloft.net,
        kuba@...nel.org, tglx@...utronix.de
Subject: Re: [PATCH net-next] net: Write lock dev_base_lock without disabling
 bottom halves.

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@...emloft.net>:

On Fri, 26 Nov 2021 17:15:29 +0100 you wrote:
> The writer acquires dev_base_lock with disabled bottom halves.
> The reader can acquire dev_base_lock without disabling bottom halves
> because there is no writer in softirq context.
> 
> On PREEMPT_RT the softirqs are preemptible and local_bh_disable() acts
> as a lock to ensure that resources, that are protected by disabling
> bottom halves, remain protected.
> This leads to a circular locking dependency if the lock acquired with
> disabled bottom halves (as in write_lock_bh()) and somewhere else with
> enabled bottom halves (as by read_lock() in netstat_show()) followed by
> disabling bottom halves (cxgb_get_stats() -> t4_wr_mbox_meat_timeout()
> -> spin_lock_bh()). This is the reverse locking order.
> 
> [...]

Here is the summary with links:
  - [net-next] net: Write lock dev_base_lock without disabling bottom halves.
    https://git.kernel.org/netdev/net-next/c/fd888e85fe6b

You are awesome, thank you!
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