netdev - Re: [PATCH net-next v2] net: try to avoid unneeded backlog flush

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Message-Id: <20200914.143916.822989187215700034.davem@davemloft.net>
Date:   Mon, 14 Sep 2020 14:39:16 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     pabeni@...hat.com
Cc:     netdev@...r.kernel.org, mtosatti@...hat.com, edumazet@...gle.com
Subject: Re: [PATCH net-next v2] net: try to avoid unneeded backlog flush

From: Paolo Abeni <pabeni@...hat.com>
Date: Thu, 10 Sep 2020 23:33:18 +0200

> flush_all_backlogs() may cause deadlock on systems
> running processes with FIFO scheduling policy.
> 
> The above is critical in -RT scenarios, where user-space
> specifically ensure no network activity is scheduled on
> the CPU running the mentioned FIFO process, but still get
> stuck.
> 
> This commit tries to address the problem checking the
> backlog status on the remote CPUs before scheduling the
> flush operation. If the backlog is empty, we can skip it.
> 
> v1 -> v2:
>  - explicitly clear flushed cpu mask - Eric
> 
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>

Applied, thank you.