linux-kernel - Re: [PATCH net-next 03/10] devlink: Serialize access to rate domains

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Message-ID: <qaznnl77zg24zh72axtv7vhbfdbxnzmr73bqr7qir5wu2r6n52@ob25uqzyxytm>
Date: Tue, 25 Feb 2025 14:36:07 +0100
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Tariq Toukan <tariqt@...dia.com>, 
	"David S. Miller" <davem@...emloft.net>, Paolo Abeni <pabeni@...hat.com>, 
	Eric Dumazet <edumazet@...gle.com>, Andrew Lunn <andrew+netdev@...n.ch>, 
	Jiri Pirko <jiri@...dia.com>, Cosmin Ratiu <cratiu@...dia.com>, 
	Carolina Jubran <cjubran@...dia.com>, Gal Pressman <gal@...dia.com>, Mark Bloch <mbloch@...dia.com>, 
	Donald Hunter <donald.hunter@...il.com>, Jonathan Corbet <corbet@....net>, 
	Saeed Mahameed <saeedm@...dia.com>, Leon Romanovsky <leon@...nel.org>, netdev@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next 03/10] devlink: Serialize access to rate domains

Wed, Feb 19, 2025 at 03:21:30AM +0100, kuba@...nel.org wrote:
>On Fri, 14 Feb 2025 13:54:43 +0100 Jiri Pirko wrote:
>> For the record, I'm still not convinced that introducing this kind of
>> shared inter-devlink lock is good idea. We spent quite a bit of painful
>> times getting rid of global devlink_mutex and making devlink locking
>> scheme nice and simple as it currently is.
>> 
>> But at the same time I admit I can't think of any other nicer solution
>> to the problem this patchset is trying to solve.
>> 
>> Jakub, any thoughts?
>
>The problem comes from having a devlink instance per function /
>port rather than for the ASIC. Spawn a single instance and the
>problem will go away 🤷️

Yeah, we currently have VF devlink ports created under PF devlink instance.
That is aligned with PCI geometry. If we have a single per-ASIC parent
devlink, this does not change and we still need to configure cross
PF devlink instances.

The only benefit I see is that we don't need rate domain, but
we can use parent devlink instance lock instead. The locking ordering
might be a bit tricky to fix though.


>
>I think we talked about this multiple times, I think at least
>once with Jake, too. Not that I remember all the details now..
>-- 
>pw-bot: cr