netdev - Re: [PATCH v4 net] net: sched: add barrier to fix packet stuck problem for lockless qdisc

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Message-Id: <165405601213.26403.11241639383072394003.git-patchwork-notify@kernel.org>
Date:   Wed, 01 Jun 2022 04:00:12 +0000
From:   patchwork-bot+netdevbpf@...nel.org
To:     Guoju Fang <gjfang@...ux.alibaba.com>
Cc:     linyunsheng@...wei.com, davem@...emloft.net, edumazet@...gle.com,
        eric.dumazet@...il.com, guoju.fgj@...baba-inc.com, kuba@...nel.org,
        netdev@...r.kernel.org, pabeni@...hat.com, rgauguey@...rayinc.com,
        sjones@...rayinc.com, vladimir.oltean@....com, vray@...rayinc.com,
        will@...nel.org
Subject: Re: [PATCH v4 net] net: sched: add barrier to fix packet stuck problem
 for lockless qdisc

Hello:

This patch was applied to netdev/net.git (master)
by Jakub Kicinski <kuba@...nel.org>:

On Sat, 28 May 2022 18:16:28 +0800 you wrote:
> In qdisc_run_end(), the spin_unlock() only has store-release semantic,
> which guarantees all earlier memory access are visible before it. But
> the subsequent test_bit() has no barrier semantics so may be reordered
> ahead of the spin_unlock(). The store-load reordering may cause a packet
> stuck problem.
> 
> The concurrent operations can be described as below,
>          CPU 0                      |          CPU 1
>    qdisc_run_end()                  |     qdisc_run_begin()
>           .                         |           .
> 
> [...]

Here is the summary with links:
  - [v4,net] net: sched: add barrier to fix packet stuck problem for lockless qdisc
    https://git.kernel.org/netdev/net/c/2e8728c955ce

You are awesome, thank you!
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