linux-kernel - Re: [PATCH net-next] devlink: Require devlink lock during device reload

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Message-ID: <YX+TUX0agfjMD0Ft@shredder>
Date:   Mon, 1 Nov 2021 09:12:17 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Leon Romanovsky <leon@...nel.org>, davem@...emloft.net,
        kuba@...nel.org
Cc:     Leon Romanovsky <leonro@...dia.com>, Jiri Pirko <jiri@...dia.com>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        edwin.peer@...adcom.com
Subject: Re: [PATCH net-next] devlink: Require devlink lock during device
 reload

On Sun, Oct 31, 2021 at 07:35:56PM +0200, Leon Romanovsky wrote:
> From: Leon Romanovsky <leonro@...dia.com>
> 
> Devlink reload was implemented as a special command which does _SET_
> operation, but doesn't take devlink->lock, while recursive devlink
> calls that were part of .reload_up()/.reload_down() sequence took it.
> 
> This fragile flow was possible due to holding a big devlink lock
> (devlink_mutex), which effectively stopped all devlink activities,
> even unrelated to reloaded devlink.
> 
> So let's make sure that devlink reload behaves as other commands and
> use special nested locking primitives with a depth of 1. Such change
> opens us to a venue of removing devlink_mutex completely, while keeping
> devlink locking complexity in devlink.c.

Jakub/Dave, I will be mostly unavailable until later this week, but I
have applied this patch to our queue and can report testing results
tomorrow. I would appreciate it if you could hold off on applying it
until then.

Thanks