Re: Linux 4.4-rc4 regression, bisected to "net: fix sock_wake_async() rcu protection"

From: Eric Dumazet
Date: Wed Dec 30 2015 - 08:55:10 EST


On Wed, 2015-12-30 at 12:32 +0100, Nicolai Stange wrote:
> Andy Lutomirski <luto@xxxxxxxxxx> writes:
>
> > On recent v4.4-rc releases, I can't run emacs. No, really, running
> > "emacs" in a GNOME 3 session makes gnome-shell think that emacs is
> > running, but no window is drawn, and the overall system UI is a bit
> > weird when the invisible emacs window is focused.
> >
> > This is 100% reproducible.
> >
> > There might be other symptoms involving gdb malfunctioning, but those
> > are, at best, sporadic. The emacs failure is entirely reliable. I
> > have no idea what the underlying failure mode is, but failure to wake
> > a socket waiter seems plausible, I also have no idea why oocalc,
> > gimp, vim, gedit, firefox, etc aren't affected.
> >
> > A somewhat unorthodox "git bisect" run blames:
> >
> > commit ceb5d58b217098a657f3850b7a2640f995032e62
> > Author: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Date: Sun Nov 29 20:03:11 2015 -0800
> >
> > net: fix sock_wake_async() rcu protection
> >
> > I've confirmed that v4.4-rc7 with that patch reverted works fine.
> >
> > Since the offending commit was apparently a security fix, simply
> > reverting it might not be the best idea.
>
> Please have a look at https://lkml.kernel.org/g/87ege73bma.fsf@xxxxxxxxx
>
> I ran into the same issue and this one fixes it for me.

Right, and the ozlabs pointers for this were :

v1:
https://patchwork.ozlabs.org/patch/561194/

v2:
https://patchwork.ozlabs.org/patch/561553/

Thanks.


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