From: Scot Doyle <lkml14@scotdoyle.com>
To: David Daney <ddaney@caviumnetworks.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>,
Jean-Christophe Plagniol-Villard <plagnioj@jcrosoft.com>,
David Daney <david.daney@cavium.com>,
Ming Lei <ming.lei@canonical.com>,
Dann Frazier <dann.frazier@canonical.com>,
Jeremy Kerr <jk@ozlabs.org>,
Peter Hurley <peter@hurleysoftware.com>,
Pavel Machek <pavel@ucw.cz>, Jonathan Liu <net147@gmail.com>,
Alistair Popple <alistair@popple.id.au>,
Jean-Philippe Brucker <jean-philippe.brucker@arm.com>,
"Chintakuntla, Radha" <Radha.Chintakuntla@caviumnetworks.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jslaby@suse.com>, David Airlie <airlied@linux.ie>,
ddaney.cavm@gmail.com, Scot Doyle <lkml14@scotdoyle.com>,
dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] fbcon: use default if cursor blink interval is not valid
Date: Thu, 19 May 2016 17:25:36 -0500 (CDT) [thread overview]
Message-ID: <alpine.DEB.2.10.1605191708400.15396@laptop> (raw)
In-Reply-To: <573DE2D0.1050402@caviumnetworks.com>
On Thu, 19 May 2016, David Daney wrote:
> On 05/18/2016 09:21 PM, Scot Doyle wrote:
> > Two current [1] and three previous [2] systems locked during boot
> > because the cursor flash timer was set using an ops->cur_blink_jiffies
> > value of 0. Previous patches attempted to solve the problem by moving
> > variable initialization earlier in the setup sequence [2].
> >
> > Use the normal cursor blink default interval of 200 ms if
> > ops->cur_blink_jiffies is not in the range specified in commit
> > bd63364caa8d. Since invalid values are not used, specific system
> > initialization timings should not cause lockups.
> >
>
> This patch just papers over the problem that you yourself introduced in commit
> bd63364caa8d ("vt: add cursor blink interval escape sequence").
>
> As you know, I have a patch that fixes the problem at the source:
> https://lkml.org/lkml/2016/5/17/455
>
> I don't like the idea of silently ignoring bad values passed in from other
> code (drivers/tty/vt/vt.c), and much less doing the check for bad values each
> time the timer expires rather than just once, where the bad value is first
> introduced.
>
> I think it would be preferable to WARN() at the site the bad value is
> introduced, so that we can easily find the real source of the problem.
> Initialize cur_blink_jiffies to a sane default value, then if something
> attempts to set it to a value that would cause soft lockup, WARN and refuse to
> change it.
I agree this approach would be cleaner and am willing to give it a try
by submitting an alternative patch and ack'ing yours. Thanks for taking
the time to critique my proposal.
next prev parent reply other threads:[~2016-05-19 22:26 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-17 18:41 [PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer David Daney
2016-05-17 20:49 ` Pavel Machek
2016-05-18 0:42 ` Ming Lei
2016-05-18 20:24 ` Scot Doyle
2016-05-18 20:38 ` David Daney
2016-05-19 4:21 ` [PATCH] fbcon: use default if cursor blink interval is not valid Scot Doyle
2016-05-19 7:25 ` Jeremy Kerr
2016-05-19 8:29 ` Ming Lei
2016-05-19 9:01 ` Pavel Machek
2016-05-19 14:22 ` Scot Doyle
2016-05-19 15:31 ` Ming Lei
2016-05-19 15:59 ` David Daney
2016-05-19 22:25 ` Scot Doyle [this message]
2016-05-19 22:31 ` [PATCH] fbcon: warn on invalid cursor blink intervals Scot Doyle
2016-05-19 22:50 ` David Daney
2016-05-20 1:21 ` Jeremy Kerr
2016-05-20 2:17 ` Ming Lei
2016-05-20 2:26 ` Jeremy Kerr
2016-05-20 2:48 ` Ming Lei
2016-05-20 5:04 ` Jeremy Kerr
2016-05-20 16:27 ` Scot Doyle
2016-05-24 1:19 ` Scot Doyle
2016-05-28 11:48 ` Henrique de Moraes Holschuh
2016-06-12 5:05 ` Chintakuntla, Radha
2016-05-28 11:45 ` Henrique de Moraes Holschuh
2016-05-19 0:27 ` [PATCH] tty: vt: Fix soft lockup in fbcon cursor blink timer Ming Lei
2016-05-19 7:08 ` Pavel Machek
2016-05-19 22:35 ` Scot Doyle
2016-05-28 11:44 ` Henrique de Moraes Holschuh
2016-06-14 16:22 ` Ping: " David Daney
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