From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Petr Mladek <pmladek@suse.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Joe Perches <joe@perches.com>,
Steven Rostedt <rostedt@goodmis.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Pavel Machek <pavel@ucw.cz>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Jan Kara <jack@suse.cz>,
Andrew Morton <akpm@linux-foundation.org>,
Jiri Slaby <jslaby@suse.com>, Andreas Mohr <andi@lisas.de>,
Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: printk: what is going on with additional newlines?
Date: Sun, 17 Sep 2017 15:26:08 +0900 [thread overview]
Message-ID: <20170917062608.GA512@tigerII.localdomain> (raw)
In-Reply-To: <20170906075554.GI8741@pathway.suse.cz>
On (09/06/17 09:55), Petr Mladek wrote:
[..]
> > but I'm not super eager to have printk-safe based buffering.
> > that's why I never posted a patch set. this approach has its
> > limitations.
>
> Ah, I am happy to read this. From the previous mails,
> I got the feeling that you were eager to go this way.
naaah, not really :)
[..]
> > I prepend every line with the CPU number that has printk()-ed it.
> > and that's helpful because one can grep and filter out messages
> > from other CPUs. it's quite OK thing to have given that messages
> > can be really mixed sometimes.
> >
> > so adding extra information to `struct printk_log' could be helpful.
> > I think we had this discussion before and you didn't want to change
> > the size of `struct printk_log' because that might break gdb/crash/etc
> > user space tools. has it changed?
>
> Yup, there should be a serious reason to change 'struct printk_log'.
> I am not sure if this is the case. But I am sure that there will
> be need to change the structure sooner or later.
>
> Anyway, it seems that we will need to update all the tools
> for the different time stamps, see
> https://lkml.kernel.org/r/1504613201-23868-1-git-send-email-prarit@redhat.com
> Then we will be more clever how painful it is.
>
>
> > may be we can #ifdef CONFIG_PRINTK_ABC them.
so... I think we don't have to update 'struct printk_log'. we can store
that "extended data" at the beginning of every message, right after the
prefix.
NOTE:
below is a very-very quick hack. so quick, that it has known problems.
- the code does not handle !PREFIX messages (like printk("foo")).
but I guess we can come up with a solution here.
- and printk_vscnprintf() should have that CONFIG_PRINTK_ABC,
which is missing in the code below.
dmesg looks like this
[ 3.338129] [ext: kworker/3:2/3] input: ETPS/2 Elantech Touchpad as /devices/platform/i8042/serio1/input/input7
[ 3.340653] [ext: systemd-udevd/0] mousedev: PS/2 mouse device common for all mice
[ 5.554184] [ext: swapper/0/0] random: crng init done
[ 33.410639] [ext: wpa_supplicant/6] IPv6: ADDRCONF(NETDEV_UP): wlp2s0: link is not ready
[ 36.812187] [ext: kworker/u16:5/1] wlp2s0: associated
[ 36.812231] [ext: kworker/1:1/1] IPv6: ADDRCONF(NETDEV_CHANGE): wlp2s0: link becomes ready
if we will ever decide to add any sort of "extended data" to every
message, then may be we can do it this way?
---
kernel/printk/printk.c | 31 ++++++++++++++++++++++++++++++-
1 file changed, 30 insertions(+), 1 deletion(-)
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index a64c52c19b03..d7380cb70fb5 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1936,6 +1936,35 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
return log_store(facility, level, lflags, 0, dict, dictlen, text, text_len);
}
+static size_t printk_vscnprintf(char *text, size_t text_sz,
+ const char *fmt, va_list args)
+{
+ size_t printed = 0;
+ bool do_prefix = false;
+
+ if (fmt[0] == KERN_SOH_ASCII) {
+ text[0] = fmt[0];
+ text[1] = fmt[1];
+
+ if (fmt[1] != 'c')
+ do_prefix = true;
+
+ fmt += 2;
+ printed = 2;
+ }
+
+ if (do_prefix) {
+ printed += snprintf(text + printed,
+ text_sz - printed,
+ "[ext: %s/%d] ",
+ current->comm,
+ smp_processor_id());
+ }
+
+ printed += vscnprintf(text + printed, text_sz - printed, fmt, args);
+ return printed;
+}
+
asmlinkage int vprintk_emit(int facility, int level,
const char *dict, size_t dictlen,
const char *fmt, va_list args)
@@ -1962,7 +1991,7 @@ asmlinkage int vprintk_emit(int facility, int level,
* The printf needs to come first; we need the syslog
* prefix which might be passed-in as a parameter.
*/
- text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
+ text_len = printk_vscnprintf(text, sizeof(textbuf), fmt, args);
/* mark and strip a trailing newline */
if (text_len && text[text_len-1] == '\n') {
next prev parent reply other threads:[~2017-09-17 6:30 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-15 2:56 [RFC][PATCHv5 00/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 01/13] printk: move printk_pending out of per-cpu Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 02/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 03/13] printk: add sync printk_emergency API Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 04/13] printk: add enforce_emergency parameter Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 05/13] printk: enable printk offloading Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 06/13] printk: register PM notifier Sergey Senozhatsky
2017-08-15 11:51 ` Rafael J. Wysocki
2017-08-16 7:31 ` Sergey Senozhatsky
2017-08-16 12:58 ` Rafael J. Wysocki
2017-08-17 5:55 ` Sergey Senozhatsky
2017-08-17 15:43 ` Rafael J. Wysocki
2017-08-17 23:19 ` Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 07/13] printk: register syscore notifier Sergey Senozhatsky
2017-08-15 11:56 ` Rafael J. Wysocki
2017-08-16 6:55 ` Sergey Senozhatsky
2017-08-16 12:59 ` Rafael J. Wysocki
2017-08-15 2:56 ` [RFC][PATCHv5 08/13] printk: set watchdog_thresh as maximum value for atomic_print_limit Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 09/13] printk: add auto-emergency enforcement mechanism Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 10/13] printk: force printk_kthread to offload printing Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 11/13] printk: always offload printing from user-space processes Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 12/13] printk: do not cond_resched() when we can offload Sergey Senozhatsky
2017-08-15 2:56 ` [RFC][PATCHv5 13/13] printk: move offloading logic to per-cpu Sergey Senozhatsky
2017-08-23 8:33 ` [RFC][PATCHv5 00/13] printk: introduce printing kernel thread Sergey Senozhatsky
2017-08-28 9:05 ` printk: what is going on with additional newlines? Pavel Machek
2017-08-28 10:28 ` Sergey Senozhatsky
2017-08-28 12:21 ` Sergey Senozhatsky
2017-08-28 12:38 ` Sergey Senozhatsky
2017-08-28 12:46 ` Pavel Machek
2017-08-29 13:40 ` Sergey Senozhatsky
2017-08-29 16:37 ` Joe Perches
2017-08-29 17:00 ` Linus Torvalds
2017-08-29 17:12 ` Linus Torvalds
2017-08-29 20:41 ` Tetsuo Handa
2017-08-29 20:51 ` Linus Torvalds
2017-09-02 6:12 ` Tetsuo Handa
2017-09-02 17:06 ` Linus Torvalds
2017-08-29 23:50 ` Steven Rostedt
2017-08-29 23:59 ` Linus Torvalds
2017-08-30 1:03 ` Sergey Senozhatsky
2017-08-30 1:10 ` Steven Rostedt
2017-08-30 1:51 ` Sergey Senozhatsky
2017-08-30 1:52 ` Joe Perches
2017-08-30 2:25 ` Sergey Senozhatsky
2017-08-30 2:31 ` Joe Perches
2017-08-30 2:47 ` Sergey Senozhatsky
2017-08-30 2:58 ` Joe Perches
2017-08-30 5:37 ` Sergey Senozhatsky
2017-09-08 10:18 ` Pavel Machek
2017-09-05 9:44 ` Petr Mladek
2017-09-05 9:59 ` Sergey Senozhatsky
2017-09-05 12:21 ` Petr Mladek
2017-09-05 12:35 ` Tetsuo Handa
2017-09-05 14:18 ` Sergey Senozhatsky
2017-09-05 13:42 ` Sergey Senozhatsky
2017-09-06 7:55 ` Petr Mladek
2017-09-17 6:26 ` Sergey Senozhatsky [this message]
2017-09-17 9:27 ` Sergey Senozhatsky
2017-09-17 15:35 ` Linus Torvalds
2017-09-18 0:46 ` Sergey Senozhatsky
2017-09-18 2:22 ` Joe Perches
2017-09-18 2:41 ` Sergey Senozhatsky
2017-09-18 2:45 ` Joe Perches
2017-09-18 2:55 ` Sergey Senozhatsky
2017-09-18 3:07 ` Joe Perches
2017-09-18 4:42 ` Sergey Senozhatsky
2017-09-01 13:19 ` Sergey Senozhatsky
2017-09-01 17:32 ` Joe Perches
2017-09-01 20:21 ` Linus Torvalds
2017-09-04 5:22 ` Sergey Senozhatsky
2017-09-04 5:41 ` Joe Perches
2017-09-05 14:54 ` Steven Rostedt
2017-09-06 2:14 ` Sergey Senozhatsky
2017-09-06 2:36 ` Linus Torvalds
2017-09-04 4:30 ` Sergey Senozhatsky
2017-09-04 5:24 ` Sergey Senozhatsky
2017-08-29 17:33 ` Sergey Senozhatsky
2017-08-29 17:52 ` Linus Torvalds
2017-08-29 18:09 ` Joe Perches
2017-08-30 1:07 ` Sergey Senozhatsky
2017-08-30 0:58 ` Sergey Senozhatsky
2017-08-29 16:48 ` Linus Torvalds
2017-08-29 17:10 ` Joe Perches
2017-08-29 17:20 ` Linus Torvalds
2017-08-29 17:33 ` Joe Perches
2017-08-29 17:36 ` Linus Torvalds
2017-08-29 17:48 ` Joe Perches
2017-08-29 20:24 ` Pavel Machek
2017-09-01 1:40 ` Sergey Senozhatsky
2017-09-01 2:04 ` Joe Perches
2017-09-01 6:59 ` Pavel Machek
2017-09-01 7:23 ` Joe Perches
2017-09-01 7:29 ` Pavel Machek
2017-09-01 11:13 ` Steven Rostedt
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