From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Aleksey Makarov <aleksey.makarov@linaro.org>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Sabrina Dubroca <sd@queasysnail.net>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
Sudeep Holla <sudeep.holla@arm.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Peter Hurley <peter@hurleysoftware.com>,
Jiri Slaby <jslaby@suse.com>, Robin Murphy <robin.murphy@arm.com>,
Steven Rostedt <rostedt@goodmis.org>,
"Nair, Jayachandran" <Jayachandran.Nair@cavium.com>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH v9 3/3] printk: fix double printing with earlycon
Date: Wed, 7 Jun 2017 18:13:22 +0900 [thread overview]
Message-ID: <20170607091322.GA568@jagdpanzerIV.localdomain> (raw)
In-Reply-To: <20170606160339.GC7604@pathway.suse.cz>
On (06/06/17 18:03), Petr Mladek wrote:
[..]
> From 142d75792d0df874e80493654311f69f6a1ca798 Mon Sep 17 00:00:00 2001
> From: Petr Mladek <pmladek@suse.com>
> Date: Tue, 6 Jun 2017 17:20:38 +0200
> Subject: [PATCH] Revert "printk: fix double printing with earlycon"
>
> The commit cf39bf58afdaabc ("printk: fix double printing with earlycon")
> caused regression to users that define both console=ttyS1 and console=ttyS0
> on the command line, see
> https://lkml.kernel.org/r/20170509082915.GA13236@bistromath.localdomain
>
> The kernel log messages always appeared only on one serial port. It is
> even documented in Documentation/admin-guide/serial-console.rst:
>
> "Note that you can only define one console per device type (serial,
> video)."
>
> The above mentioned commit changed the order in which the command line
> parameters are searched. As a result, the kernel log messages go to
> the last mentioned ttyS* instead of the first one.
>
> We long thought that using two console=ttyS* on the command line
> did not make sense. But then we realized that console= parameters
> were handled also by systemd, see
> http://0pointer.de/blog/projects/serial-console.html
>
> "By default systemd will instantiate one serial-getty@.service on
> the main kernel console, if it is not a virtual terminal."
>
> where
>
> "[4] If multiple kernel consoles are used simultaneously, the main
> console is the one listed first in /sys/class/tty/console/active,
> which is the last one listed on the kernel command line."
>
> This puts the original report into another light. The system is running
> in qemu. The first serial port is used to store the messages into a file.
> The second one is used to login to the system via a socket. It depends
> on systemd and the historic kernel behavior.
>
> By other words, systemd causes that it makes sense to define both
> console=ttyS1 console=ttyS0 on the command line. The kernel fix
> caused regression related to userspace (systemd) and need to be
> reverted.
>
> In addition, it went out that the fix helped only partially.
> The messages still were duplicated when the boot console was
> removed early by late_initcall(printk_late_init). Then the entire
> log was replayed when the same console was registered as a normal one.
>
> This reverts commit cf39bf58afdaabc0b86f141630fb3fd18190294e.
FWIW,
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
the whole thing is too fragile and, may be, it deserves a rewrite.
I agree with the decision to revert the patch. a user space visible
regression is a pretty annoying thing; even a rare one. it takes ~1-2
years until kernel release hits major vendors/users so the biggest part
of regressions might be years away, but in the meantime we can grow a
number of new setups that will depend on a new console= behavior. so
I'd prefer to revert early.
Petr, Aleksey, many thanks, good work.
-ss
prev parent reply other threads:[~2017-06-07 9:13 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-15 10:28 [PATCH v5 0/3] printk: fix double printing with earlycon Aleksey Makarov
2017-03-15 10:28 ` [PATCH v5 1/3] printk: fix name/type/scope of preferred_console var Aleksey Makarov
2017-03-15 10:28 ` [PATCH v5 2/3] printk: rename selected_console -> preferred_console Aleksey Makarov
2017-03-15 10:28 ` [PATCH v5 3/3] printk: fix double printing with earlycon Aleksey Makarov
2017-03-15 16:58 ` Petr Mladek
2017-03-16 7:30 ` Sergey Senozhatsky
2017-03-16 10:36 ` Aleksey Makarov
2017-03-16 13:54 ` Petr Mladek
2017-03-17 10:32 ` Aleksey Makarov
2017-03-17 11:43 ` [PATCH v6 " Aleksey Makarov
2017-03-17 13:34 ` Aleksey Makarov
2017-03-17 13:43 ` [PATCH v7 " Aleksey Makarov
2017-03-20 6:16 ` Sergey Senozhatsky
2017-03-20 10:03 ` [PATCH v8 " Aleksey Makarov
2017-03-27 14:14 ` Petr Mladek
2017-03-27 16:28 ` Aleksey Makarov
2017-03-28 2:04 ` Sergey Senozhatsky
2017-03-28 12:56 ` Petr Mladek
2017-03-30 5:55 ` Sergey Senozhatsky
2017-04-04 11:12 ` Petr Mladek
2017-04-05 18:26 ` Aleksey Makarov
2017-04-05 20:20 ` [PATCH v9 " Aleksey Makarov
2017-04-05 21:57 ` Andy Shevchenko
2017-04-06 4:44 ` Aleksey Makarov
2017-04-10 14:22 ` Petr Mladek
2017-04-10 18:00 ` Aleksey Makarov
2017-04-11 1:54 ` Sergey Senozhatsky
2017-04-11 7:43 ` Petr Mladek
2017-04-12 6:24 ` Aleksey Makarov
2017-05-09 8:29 ` Sabrina Dubroca
2017-05-11 8:24 ` Sergey Senozhatsky
2017-05-11 8:41 ` Sergey Senozhatsky
2017-05-11 11:32 ` Sergey Senozhatsky
2017-05-11 21:17 ` Aleksey Makarov
2017-05-12 1:11 ` Sergey Senozhatsky
2017-05-11 21:13 ` Aleksey Makarov
2017-05-12 12:57 ` Petr Mladek
2017-05-12 13:46 ` Petr Mladek
2017-05-14 21:01 ` Aleksey Makarov
2017-05-13 11:48 ` Sergey Senozhatsky
2017-05-14 20:37 ` Aleksey Makarov
2017-05-18 15:49 ` Petr Mladek
2017-05-26 9:37 ` Aleksey Makarov
2017-06-01 12:03 ` Petr Mladek
2017-06-06 14:31 ` Petr Mladek
2017-06-06 16:03 ` Petr Mladek
2017-06-07 9:13 ` Sergey Senozhatsky [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170607091322.GA568@jagdpanzerIV.localdomain \
--to=sergey.senozhatsky.work@gmail.com \
--cc=Jayachandran.Nair@cavium.com \
--cc=aleksey.makarov@linaro.org \
--cc=gregkh@linuxfoundation.org \
--cc=jslaby@suse.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-serial@vger.kernel.org \
--cc=peter@hurleysoftware.com \
--cc=pmladek@suse.com \
--cc=robin.murphy@arm.com \
--cc=rostedt@goodmis.org \
--cc=sd@queasysnail.net \
--cc=sergey.senozhatsky@gmail.com \
--cc=sudeep.holla@arm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).