Hi Filipe,
On 06/03/2015 01:03 AM, Filipe Brandenburger wrote:
> Hi,
>
> This seems to be a regression introduced in this commit:
> d2b6f44779d3 ("n_tty: Fix signal handling flushes")
>
> The problem is that pressing Ctrl+C on a shell through SSH is "eating"
> the output, which is usually a literal "^C", a newline and the $PS1
> prompt.
Thanks for the report.
But I'm having trouble reproducing what you observe using either
native localhost or 2 machines, so this may be specific to qemu.
I assume you're shelling onto the vm? Is this an x86 vm?
> I straced both bash and the sshd for that connection and caught it on
> a time while the problem happened. It turns out bash was indeed
> printing the "^C", newline and $PS1 but the sshd process was never
> receiving it, so it was being lost somewhere in the pty code...
>
> I tried bisecting it but it was hard since the problem wouldn't always
> reproduce...
Could echo be off at the moment the signal char is processed?
IOW, what are you interrupting?
> But I booted with 3.9.8 and used the vm for many hours,
> didn't notice it once, booted on 4.1-rc6 again, used it for a while
> and noticed the problem was there,
I could see how a pty closing bug might cause this but that was fixed
for 4.1-rc3 (and was only just added to the 4.0-stable tree), so
doesn't explain observing this on 4.1-rc6.
Regards,
Peter Hurley
> then reverted commit d2b6f44779d3,
> rebuilt, boot it, used it for a few hours and (so far) haven't noticed
> the problem back.
>
> I'm using Arch Linux on a qemu/kvm. I noticed this problem first with
> kernel 4.0.4 from Arch, but then I tried upstream kernels and I
> noticed the same on 4.0, 4.0.4-upstream, 4.1-rc5 and 4.1-rc6.
>
> If I have some time, I'll start digging into it to figure out if I can
> trace some kernel structures when I manage to reproduce the problem.
> If you'd like me to add a kernel patch and possibly execute some
> commands for tracing while I try to reproduce the problem (to confirm
> a hypothesis you may have?) let me know, I'd be happy to help in
> trying to figure this one out.
>
> Kernel bugzilla is here:
> https://bugzilla.kernel.org/show_bug.cgi?id=99351
>
> Cheers!
> Filipe
>
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