linux-kernel - Fwd: Regression: patch " hvc_console: display printk messages on console." causing infinite loop with 3.2-rc0 + Xen.

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Message-ID: <CAB8Rdapo4gfEKOd2Xez7kqPHJR-1+emDvGpCq+Kv8yTtG9XYdg@mail.gmail.com>
Date:	Thu, 27 Oct 2011 07:50:44 -0700
From:	Miche Baker-Harvey <miche@...gle.com>
To:	linux-kernel@...r.kernel.org
Subject: Fwd: Regression: patch " hvc_console: display printk messages on
 console." causing infinite loop with 3.2-rc0 + Xen.

<plain text forwarding>

Bummer.  Sorry about that.
Konrad, could you give me a hand figuring out what's up with this -
I'm not running Zen here.  (If there's a test suite I could have run,
mea culpa, and please point me in the right direction.)

The "console [hvc0] enabled" message is coming from register_console()
in printk.c, and it doesn't have any loops.
It's called from hvc_console_init(), hvc_instantiate(), and
hvc_alloc(), none of which have loops.  The call in hvc_alloc() is the
one I added, so either I've inadvertently made one of the other two
repeat (I'm guestting hvc_instantiate() is the one you're using), or
you're infinitely calling hvc_alloc().  There's a calls to hvc_alloc()
in hvc_xen.c::xen_hvc_init(), and in init_port_console() in
virtio_console.c, but again, no loops.  Similarly for
hvc_instantiate().

So, could I trouble you to put a breakpoint in register_console() and
send me the stack?

Thanks,
Miche

On Wed, Oct 26, 2011 at 10:48 PM, Greg KH <gregkh@...e.de> wrote:
>
> On Thu, Oct 27, 2011 at 01:30:08AM -0400, Konrad Rzeszutek Wilk wrote:
> > Hey Miche.
> >
> > The git commit 361162459f62dc0826b82c9690a741a940f457f0:
> >
> >     hvc_console: display printk messages on console.
> >
> > is causing an infinite loop when booting Linux under Xen, as so:
> >
> > [    2.382984] console [hvc0] enabled
> > [    2.382984] console [hvc0] enabled
> > [    2.382984] console [hvc0] enabled
> > [    2.382984] console [hvc0] enabled
> > [    2.382984] console [hvc0] enabled
> > [    2.382984] console [hvc0] enabled
> > ..
> >
> > (see attached file titled bad.log)
> >
> > If I use Linus's latest git tree and revert your patch I get the kernel
> > to bootup (see good.log file),
>
> Ick, not good, thanks for letting us know.
>
> Miche, want me to just revert this, or do you think you can fix it?
>
> thanks,
>
> greg k-h
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