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From: "Manuel Schölling" <manuel.schoelling@gmx.de>
To: Adam Borowski <kilobyte@angband.pl>
Cc: plagnioj@jcrosoft.com, tomi.valkeinen@ti.com, jslaby@suse.cz,
	gregkh@linuxfoundation.org, linux-fbdev@vger.kernel.org,
	linux-kernel@vger.kernel.org, andrey_utkin@fastmail.com
Subject: Re: [PATCH v5 2/2] console: Add persistent scrollback buffers for all VGA consoles
Date: Tue, 22 Nov 2016 17:56:42 +0100	[thread overview]
Message-ID: <1479833802.19820.8.camel@gmx.de> (raw)
In-Reply-To: <20161121201704.GA29655@angband.pl>

Hi Adam,

On Mo, 2016-11-21 at 21:17 +0100, Adam Borowski wrote:
> On Sun, Nov 20, 2016 at 10:58:08PM +0100, Manuel Schölling wrote:
> > Add a scrollback buffers for each VGA console. The benefit is that
> > the scrollback history is not flushed when switching between consoles
> > but is persistent.
> > The buffers are allocated on demand when a new console is opened.
> > 
> > This breaks tools like clear_console that rely on flushing the
> > scrollback history by switching back and forth between consoles
> > which is why this feature is disabled by default.
> > Use the escape sequence \e[3J instead for flushing the buffer.

> First, big thanks for this fix, it's something that greatly annoyed me
> since forever!
Yeah, me too! ;)

> The thing about clear_console is unfortunate: they abused the bug you're
> fixing.  I've asked to use \e[3J (https://bugs.debian.org/845177) so there's
> hope it'll be applied in stretch; with Debian configuring its glibc to
> support only kernels from two releases before (in jessie that's 2.6.32, in
> stretch 3.2)[1] there's hope we can flip the default in several years.
> 
> Do you suspect any other program relies on VT switch to clear the
> scrollback?
Not, AFAIK. Although I do not have a complete list of programs that are
suppose to do that.

> But alas, this commit breaks that very \e[3J.  It does only a \e[2J, leaving
> the scrollback uncleared.  For comparison, both mainline and with just your
> preparatory commit, \e[3J works as expected.
Really? All my tests worked fine: I compiled the kernel with the latest patches, started the kernel in QEMU and then did

  $ openvt /bin/sh
  $ echo -e '\e[3J' # scrollback buffer was flushed correctly
  $ chvt 2
  $ echo -e '\e[3J' # scrollback buffer was flushed correctly

Can you tell me how you tested it? Maybe I can reproduce the bug.

Thanks for spending the time to test it!

Bye,

Manuel

  reply	other threads:[~2016-11-22 16:56 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20161118005309.GC26324@dell-m4800.home>
2016-11-20 21:58 ` [PATCH v5 0/2] console: Add persistent scrollback buffers for all VGA console Manuel Schölling
2016-11-20 21:58   ` [PATCH v5 1/2] console: Move scrollback data into its own struct Manuel Schölling
2016-11-20 21:58   ` [PATCH v5 2/2] console: Add persistent scrollback buffers for all VGA consoles Manuel Schölling
2016-11-20 22:23     ` kbuild test robot
2016-11-21 20:17     ` Adam Borowski
2016-11-22 16:56       ` Manuel Schölling [this message]
2016-11-23 17:33         ` Adam Borowski
2016-11-27 16:51           ` [PATCH v7 0/3] " Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 1/3] console: Move scrollback data into its own struct Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 2/3] console: Add callback to flush scrollback buffer to consw struct Manuel Schölling
2016-11-27 16:51             ` [PATCH v7 3/3] console: Add persistent scrollback buffers for all VGA consoles Manuel Schölling
2016-11-27 21:37             ` [PATCH v7 0/3] " Andrey Utkin
2016-11-27 23:15               ` Adam Borowski
2016-11-27 23:30                 ` Jakub Wilk
2016-11-28  0:02                 ` Andrey Utkin
2016-11-28 21:28               ` Manuel Schölling
2016-11-29 10:01                 ` Andrey Utkin
2016-11-29 10:44                   ` Adam Borowski
2016-11-29 16:35                   ` Manuel Schölling
2016-12-01 21:03                   ` Manuel Schölling
2016-12-01 21:31                     ` Andrey Utkin
2016-11-27 23:53             ` Adam Borowski
2016-11-28 21:23               ` Manuel Schölling
2016-11-23 17:33       ` [PATCH v5 2/2] " Manuel Schölling

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