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Groups > linux.kernel > #1721497

Re: printk: what is going on with additional newlines?

From Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Newsgroups linux.kernel
Subject Re: printk: what is going on with additional newlines?
Date 2017-08-28 12:30 +0200
Message-ID <ujpsS-4p8-35@gated-at.bofh.it> (permalink)
References <ueAff-3Y4-3@gated-at.bofh.it> <ujods-3Ju-7@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On (08/28/17 11:05), Pavel Machek wrote:
> Hi!
> 
> In 4.13-rc, printk("foo"); printk("bar"); seems to produce
> foo\nbar. That's... quite surprising/unwelcome. What is going on
> there? Are timestamps responsible?

well, one thing we know for sure it is not related to this patch set  ;)


does any of the below patches fix the problem for you?

basically it sets up the rule -- if we don't have LOG_NEWLINE lflags
then we enforce LOG_CONT.

---

@@ -1721,9 +1723,13 @@ asmlinkage int vprintk_emit(int facility, int level,
 	text_len = vscnprintf(text, sizeof(textbuf), fmt, args);
 
 	/* mark and strip a trailing newline */
-	if (text_len && text[text_len-1] == '\n') {
-		text_len--;
-		lflags |= LOG_NEWLINE;
+	if (text_len) {
+		if (text[text_len-1] == '\n') {
+			text_len--;
+			lflags |= LOG_NEWLINE;
+		} else {
+			lflags |= LOG_CONT;
+		}
 	}
 
 	/* strip kernel syslog prefix and extract log level or control flags */


---


=== 8< === 8< ===


or... an alternative "solution"

---

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index fc47863f629c..5fd567abc5e6 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -1670,7 +1670,9 @@ static size_t log_output(int facility, int level, enum log_flags lflags, const c
 	 * write from the same process, try to add it to the buffer.
 	 */
 	if (cont.len) {
-		if (cont.owner == current && (lflags & LOG_CONT)) {
+		if (cont.owner == current &&
+				((lflags & LOG_CONT) ||
+				 !(lflags & LOG_NEWLINE))) {
 			if (cont_add(facility, level, lflags, text, text_len))
 				return text_len;
 		}


---

	-ss

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Thread

printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-28 11:10 +0200
  Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 12:30 +0200
    Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 14:30 +0200
      Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-28 14:40 +0200
      Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-28 14:50 +0200
        Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-29 15:50 +0200
          Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 18:40 +0200
          Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:10 +0200
            Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:20 +0200
              Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-08-29 22:50 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 23:00 +0200
                Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-02 08:20 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-02 19:10 +0200
              Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-08-30 02:00 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-30 02:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:10 +0200
                Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-08-30 03:20 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:50 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 04:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 04:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 04:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 04:50 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-30 05:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 07:40 +0200
                Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-08 12:20 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-05 11:50 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-05 12:10 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-05 14:30 +0200
                Re: printk: what is going on with additional newlines? Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> - 2017-09-05 14:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-05 16:30 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-05 15:50 +0200
                Re: printk: what is going on with additional newlines? Petr Mladek <pmladek@suse.com> - 2017-09-06 10:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-09-01 15:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 19:40 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-01 22:30 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 07:30 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-04 07:50 +0200
                Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-09-05 17:00 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-06 04:20 +0200
                Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-06 04:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 06:40 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-04 07:30 +0200
            Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky@gmail.com> - 2017-08-29 19:40 +0200
              Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 20:00 +0200
                Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 20:10 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:10 +0200
                Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-08-30 03:00 +0200
  Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 18:50 +0200
    Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:20 +0200
      Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:30 +0200
        Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:40 +0200
          Re: printk: what is going on with additional newlines? Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-29 19:40 +0200
            Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-08-29 19:50 +0200
    Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-08-29 22:30 +0200
      Re: printk: what is going on with additional newlines? Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com> - 2017-09-01 03:50 +0200
        Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 04:10 +0200
          Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-01 09:00 +0200
            Re: printk: what is going on with additional newlines? Joe Perches <joe@perches.com> - 2017-09-01 09:30 +0200
        Re: printk: what is going on with additional newlines? Pavel Machek <pavel@ucw.cz> - 2017-09-01 09:30 +0200
          Re: printk: what is going on with additional newlines? Steven Rostedt <rostedt@goodmis.org> - 2017-09-01 13:20 +0200

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