linux-kernel - Re: [PATCH net 2/3] mptcp: remove unneeded lock when listing scheds

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Message-ID: <4ca239db-6a05-4735-916c-73cee0ee22a0@kernel.org>
Date: Wed, 23 Oct 2024 16:13:36 +0200
From: Matthieu Baerts <matttbe@...nel.org>
To: Simon Horman <horms@...nel.org>
Cc: mptcp@...ts.linux.dev, Mat Martineau <martineau@...nel.org>,
 Geliang Tang <geliang@...nel.org>, "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Gregory Detal <gregory.detal@...il.com>,
 Shuah Khan <shuah@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH net 2/3] mptcp: remove unneeded lock when listing scheds

Hi Simon,

Thank you for the reviews!

On 23/10/2024 14:21, Simon Horman wrote:
> On Mon, Oct 21, 2024 at 12:25:27PM +0200, Matthieu Baerts (NGI0) wrote:
>> mptcp_get_available_schedulers() needs to iterate over the schedulers'
>> list only to read the names: it doesn't modify anything there.
>>
>> In this case, it is enough to hold the RCU read lock, no need to combine
>> this with the associated spin lock.
>>
>> Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers")
>> Cc: stable@...r.kernel.org
>> Suggested-by: Paolo Abeni <pabeni@...hat.com>
>> Reviewed-by: Geliang Tang <geliang@...nel.org>
>> Signed-off-by: Matthieu Baerts (NGI0) <matttbe@...nel.org>
> 
> I do wonder if it would be more appropriate to route this via net-next
> (without a fixes tag) rather than via net. But either way this looks good
> to me.
Good point. On one hand, I marked it as a fix, because when working on
the patch 1/3, we noticed these spin_(un)lock() were not supposed to be
there in the first place. On the other hand, even it's fixing a small
performance issue, it is not fixing a regression.

I think it is easier to route this via -net, but I'm fine if it is
applied in net-next.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.