netdev - Re: [RFC PATCH net-next 9/9] net-sysfs: remove the use of rtnl_trylock/restart

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Date:   Wed, 06 Oct 2021 10:03:41 +0200
From:   Antoine Tenart <atenart@...nel.org>
To:     Michal Hocko <mhocko@...e.com>
Cc:     davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        gregkh@...uxfoundation.org, ebiederm@...ssion.com,
        stephen@...workplumber.org, herbert@...dor.apana.org.au,
        juri.lelli@...hat.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH net-next 9/9] net-sysfs: remove the use of rtnl_trylock/restart_syscall

Quoting Michal Hocko (2021-10-06 08:45:58)
> On Tue 28-09-21 14:55:00, Antoine Tenart wrote:
> > The ABBA deadlock avoided by using rtnl_trylock and restart_syscall was
> > fixed in previous commits, we can now remove the use of this
> > trylock/restart logic and have net-sysfs operations not spinning when
> > rtnl is already taken.
> 
> Shouldn't those lock be interruptible or killable at least? As mentioned
> in other reply we are seeing multiple a contention on some sysfs file
> because mlx driver tends to do some heavy lifting in its speed callback
> so it would be great to be able to interact with waiters during that
> time.

Haven't thought much about this, but it should be possible to use
rtnl_lock_killable. I think this should be a patch on its own with its
own justification though (to help bisecting). But that is easy to do
once the trylock logic is gone.

Thanks,
Antoine