netdev - Re: [GIT PULL] Networking for v6.16-rc6 (follow up)

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Message-ID: <CAHk-=wj1Y3LfREoHvT4baucVJ5jvy0cMydcPVQNXhprdhuE2AA@mail.gmail.com>
Date: Fri, 11 Jul 2025 11:33:10 -0700
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Jakub Kicinski <kuba@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Simona Vetter <simona@...ll.ch>, Dave Airlie <airlied@...il.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	pabeni@...hat.com, dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [GIT PULL] Networking for v6.16-rc6 (follow up)

[ Added in some drm people too, just to give a heads-up that it isn't
all their fault ]

On Fri, 11 Jul 2025 at 08:10, Jakub Kicinski <kuba@...nel.org> wrote:
>
>  The Netlink fixes (on top of the tree) restore
> operation of iw (WiFi CLI) which uses sillily small recv buffer,
> and is the reason for this "emergency PR".

So this was "useful" in the sense that it seems to have taken my
"random long delays at initial graphical login" and made them
"reliable hangs at early boot time" instead.

I originally blamed the drm tree, because there were some other issues
in there with reference counting - and because the hang happened at
that "start graphical environment", but now it really looks like two
independent issues, where the netlink issues cause the delay, and the
drm object refcounting issues were entirely separate and coincidental.

I suspect that there is bootup code that needs more than that "just
one skb", and that all the recent issues with netlink sk_rmem_alloc
are broken and need reverting.

Because this "emergency PR" does seem to have turned my "annoying
problem with timeouts at initial login" into "now it doesn't boot at
all".

Which is good in that the random timeouts and delays were looking like
a nightmare to bisect, and now it looks like at least the cause of
them is more clear.

But it's certainly not good in the sense of "we're at almost rc6, we
shouldn't be having these kinds of issues".

The machine I see this on doesn't actually use WiFi at all, but there
*is* a WiFi chip in it, I just turn off that interface in favor of the
wired ports.

But obviously there might also be various other netlink users that are
unhappy with the accounting changes, so the WiFi angle may be a red
herring.

            Linus