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

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Message-ID: <20241025100051.GN1202098@kernel.org>
Date: Fri, 25 Oct 2024 11:00:51 +0100
From: Simon Horman <horms@...nel.org>
To: Matthieu Baerts <matttbe@...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

On Wed, Oct 23, 2024 at 04:13:36PM +0200, Matthieu Baerts wrote:
> 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.

Understood. FTR, I don't feel strongly about this either way.