netdev - Re: [PATCH wireless-next 0/3] netlink carrier race workaround

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Date: Sat, 02 Dec 2023 11:06:36 +0100
From: Johannes Berg <johannes@...solutions.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH wireless-next 0/3] netlink carrier race workaround

On Fri, 2023-12-01 at 16:28 -0800, Jakub Kicinski wrote:
> On Fri,  1 Dec 2023 11:41:14 +0100 Johannes Berg wrote:
> > So I had put this aside for a while, but really got annoyed by all
> > the test failures now ... thinking about this again I basically now
> > arrived at a variant of solution #3 previously outlined, and I've
> > kind of convinced myself that userspace should always get an event
> > with a new carrier_up_count as it does today.
> 
> Would it work if we exposed "linkwatch is pending" / "link is
> transitioning" bit to user space?

Not sure, not by much or more than what this did? It's basically the
same, I think: I exposed the carrier_up_count at the kernel time, so if
userspace hasn't seen an event with a value >= that it knows the link is
transitioning.

> Even crazier, would it help if we had rtnl_getlink() run
> linkwatch for the target link if linkwatch is pending?

Sure, if we were to just synchronize that at the right time (doesn't
even need to be rtnl_getlink, could be a new operation) that'd solve the
issue too, perhaps more easily.

johannes