Re: Patch "tty: vt: Fix soft lockup in fbcon cursor blink timer." has been added to the 3.14-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, Jul 25, 2016 at 09:02:28AM -0500, Scot Doyle wrote:
> On Sun, 24 Jul 2016, gregkh@linuxfoundation.org wrote:
> > This is a note to let you know that I've just added the patch titled
> > 
> >     tty: vt: Fix soft lockup in fbcon cursor blink timer.
> > 
> > to the 3.14-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > The filename of the patch is:
> >      tty-vt-fix-soft-lockup-in-fbcon-cursor-blink-timer.patch
> > and it can be found in the queue-3.14 subdirectory.
> > 
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> > 
> > 
> > >From 1b45996d2ebf9680ccd0db875fc668aa025f40fd Mon Sep 17 00:00:00 2001
> > From: David Daney <david.daney@cavium.com>
> > Date: Tue, 17 May 2016 11:41:04 -0700
> > Subject: tty: vt: Fix soft lockup in fbcon cursor blink timer.
> > 
> > From: David Daney <david.daney@cavium.com>
> > 
> > commit 1b45996d2ebf9680ccd0db875fc668aa025f40fd upstream.
> > 
> > We are getting somewhat random soft lockups with this signature:
> > 
> > [   86.992215] [<fffffc00080935e0>] el1_irq+0xa0/0x10c
> > [   86.997082] [<fffffc000841822c>] cursor_timer_handler+0x30/0x54
> > [   87.002991] [<fffffc000810ec44>] call_timer_fn+0x54/0x1a8
> > [   87.008378] [<fffffc000810ef88>] run_timer_softirq+0x1c4/0x2bc
> > [   87.014200] [<fffffc000809077c>] __do_softirq+0x114/0x344
> > [   87.019590] [<fffffc00080af45c>] irq_exit+0x74/0x98
> > [   87.024458] [<fffffc00080fac20>] __handle_domain_irq+0x98/0xfc
> > [   87.030278] [<fffffc000809056c>] gic_handle_irq+0x94/0x190
> > 
> > This is caused by the vt visual_init() function calling into
> > fbcon_init() with a vc_cur_blink_ms value of zero.  This is a
> > transient condition, as it is later set to a non-zero value.  But, if
> > the timer happens to expire while the blink rate is zero, it goes into
> > an endless loop, and we get soft lockup.
> > 
> > The fix is to initialize vc_cur_blink_ms before calling the con_init()
> > function.
> > 
> > Signed-off-by: David Daney <david.daney@cavium.com>
> > Acked-by: Pavel Machek <pavel@ucw.cz>
> > Tested-by: Ming Lei <ming.lei@canonical.com>
> > Acked-by: Scot Doyle <lkml14@scotdoyle.com>
> > Tested-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > 
> > ---
> >  drivers/tty/vt/vt.c |    1 +
> >  1 file changed, 1 insertion(+)
> > 
> > --- a/drivers/tty/vt/vt.c
> > +++ b/drivers/tty/vt/vt.c
> > @@ -742,6 +742,7 @@ static void visual_init(struct vc_data *
> >  	vc->vc_complement_mask = 0;
> >  	vc->vc_can_do_color = 0;
> >  	vc->vc_panic_force_write = false;
> > +	vc->vc_cur_blink_ms = DEFAULT_CURSOR_BLINK_MS;
> >  	vc->vc_sw->con_init(vc, init);
> >  	if (!vc->vc_complement_mask)
> >  		vc->vc_complement_mask = vc->vc_can_do_color ? 0x7700 : 0x0800;
> > 
> > 
> > Patches currently in stable-queue which might be from david.daney@cavium.com are
> > 
> > queue-3.14/tty-vt-fix-soft-lockup-in-fbcon-cursor-blink-timer.patch
> > 
> 
> Hi Greg,
> 
> This patch is only necessary for >= 4.2 kernels.

Yeah, that was obvious when it broke the 3.14 build, so I removed it
from the queue yesterday :)

thanks,

greg k-h