linux-kernel - Re: kernel CI: printk loglevels in kernel boot logs?

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Message-ID: <20171123031408.2p34znajairgfnbo@wfg-t540p.sh.intel.com>
Date:   Thu, 23 Nov 2017 11:14:08 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Kevin Hilman <khilman@...libre.com>,
        Mark Brown <broonie@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: kernel CI: printk loglevels in kernel boot logs?

On Thu, Nov 23, 2017 at 11:59:57AM +0900, Sergey Senozhatsky wrote:
>On (11/22/17 20:52), Fengguang Wu wrote:
>[..]
>> > well, I think that that "consoles_format=syslog" command line parameter
>> > will be enabled only by those who actually want to have it - Fengguang's
>> > build robot and kernelCI (+ may be more setups).  so I'd probably assume
>> > there are low risks here. may be I'm wrong.
>>
>> Yes, since it needs explicit enabling, local parsers should stay
>> working. Unless we send dmesg to other developers, but then they
>> might also receive $(dmesg --raw) outputs and need to handle <%u>
>> prefixes, too.
>>
>> > I think it makes sense to have syslog's format "<%u>[timestamp] text\n"
>> > on serial consoles (time stamp when PRINTK_TIME set; <%u> when
>> > consoles_format=syslog set).
>>
>> Thanks. Since the 0day scripts can already parse that format (code
>> is listed below), we should quickly benefit from that feature when
>> it's mainlined.
>
>okay... who's going to send the patch? kernelCI folks?
>
>I have some sort of a patch. added console_msg_format= with the only

The patch looks good to me. Perhaps you can send it out after getting
review comments from kernelci folks?

Reviewed-by: Fengguang Wu <fengguang.wu@...el.com>

Thanks,
Fengguang

>available option so far - "syslog". may be people would want to have
>boot time, etc. on their consoles. who knows. may be msg_format will
>be extended someday in the future or may be not, and we can do
>something like "console_format_syslog" (or any better name).
>
>Not-yet-signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
>---
> Documentation/admin-guide/kernel-parameters.txt | 11 +++++++++++
> kernel/printk/printk.c                          | 21 ++++++++++++++++++++-
> 2 files changed, 31 insertions(+), 1 deletion(-)
>
>diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>index 62436bd5f34a..42113e5181b2 100644
>--- a/Documentation/admin-guide/kernel-parameters.txt
>+++ b/Documentation/admin-guide/kernel-parameters.txt
>@@ -640,6 +640,17 @@
> 			console=brl,ttyS0
> 		For now, only VisioBraille is supported.
>
>+	console_msg_format=
>+			[KNL] Control message format
>+			By default we print messages in "[time stamp] text\n"
>+			format (time stamp may not be printed, depending on
>+			CONFIG_PRINTK_TIME or `printk_time' param).
>+		syslog
>+			Switch to syslog format (similar to "dmesg --raw" or
>+			reading from /proc/kmsg): "<%u>[time stamp] text\n"
>+			IOW, each message is getting prepended with the
>+			facility and loglevel prefix.
>+
> 	consoleblank=	[KNL] The console blank (screen saver) timeout in
> 			seconds. A value of 0 disables the blank timer.
>                        Defaults to 0.
>diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
>index 5d81206a572d..034f3ad85f5b 100644
>--- a/kernel/printk/printk.c
>+++ b/kernel/printk/printk.c
>@@ -277,6 +277,13 @@ EXPORT_SYMBOL(console_set_on_cmdline);
> /* Flag: console code may call schedule() */
> static int console_may_schedule;
>
>+enum con_msg_format {
>+	MSG_FORMAT_DEFAULT = 1,
>+	MSG_FORMAT_SYSLOG = 2,
>+};
>+
>+static int console_msg_format = MSG_FORMAT_DEFAULT;
>+
> /*
>  * The printk log buffer consists of a chain of concatenated variable
>  * length records. Every record starts with a record header, containing
>@@ -1913,6 +1920,15 @@ static int __add_preferred_console(char *name, int idx, char *options,
> 	c->index = idx;
> 	return 0;
> }
>+
>+static int __init console_msg_format_setup(char *str)
>+{
>+	if (!strncmp(str, "syslog", 6))
>+		console_msg_format = MSG_FORMAT_SYSLOG;
>+	return 1;
>+}
>+__setup("console_msg_format=", console_msg_format_setup);
>+
> /*
>  * Set up a console.  Called via do_early_param() in init/main.c
>  * for each "console=" parameter in the boot command line.
>@@ -2215,7 +2231,10 @@ void console_unlock(void)
> 			goto skip;
> 		}
>
>-		len += msg_print_text(msg, false, text + len, sizeof(text) - len);
>+		len += msg_print_text(msg,
>+				console_msg_format & MSG_FORMAT_SYSLOG,
>+				text + len,
>+				sizeof(text) - len);
> 		if (nr_ext_console_drivers) {
> 			ext_len = msg_print_ext_header(ext_text,
> 						sizeof(ext_text),
>-- 
>2.15.0
>